ORCID Profile
0000-0001-5226-871X
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Physical Oceanography | Atmospheric Dynamics | Climate Change Processes | Atmospheric Sciences | Oceanography | Water Resources Engineering | Surfacewater Hydrology | Physical Geography and Environmental Geoscience | Oceanography | Glaciology | Climatology (excl. Climate Change Processes) | Physical oceanography | Biological oceanography | Atmospheric dynamics | Fisheries Management |
ANZSRC Socio-Economic Objective (SEO)
Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Climate Variability (excl. Social Impacts) | Climate Change Models | Atmospheric Processes and Dynamics | Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Wild Caught Tuna | Water Allocation and Quantification | Natural Hazards in Coastal and Estuarine Environments | Expanding Knowledge in the Environmental Sciences | Expanding Knowledge in the Earth Sciences | Effects of Climate Change and Variability on the South Pacific (excl. Australia and New Zealand) (excl. Social Impacts)
Related Links
Publications
Dynamics and Predictability of El Niño–Southern Oscillation: An Australian Perspective on Progress and Challenges
Publisher: American Meteorological Society
Date: 03-2019
Abstract: El Niño and La Niña, the warm and cold phases of El Niño–Southern Oscillation (ENSO), cause significant year-to-year disruptions in global climate, including in the atmosphere, oceans, and cryosphere. Australia is one of the countries where its climate, including droughts and flooding rains, is highly sensitive to the temporal and spatial variations of ENSO. The dramatic impacts of ENSO on the environment, society, health, and economies worldwide make the application of reliable ENSO predictions a powerful way to manage risks and resources. An improved understanding of ENSO dynamics in a changing climate has the potential to lead to more accurate and reliable ENSO predictions by facilitating improved forecast systems. This motivated an Australian national workshop on ENSO dynamics and prediction that was held in Sydney, Australia, in November 2017. This workshop followed the aftermath of the 2015/16 extreme El Niño, which exhibited different characteristics to previous extreme El Niños and whose early evolution since 2014 was challenging to predict. This essay summarizes the collective workshop perspective on recent progress and challenges in understanding ENSO dynamics and predictability and improving forecast systems. While this essay discusses key issues from an Australian perspective, many of the same issues are important for other ENSO-affected countries and for the international ENSO research community.
Drivers of the sudden Antarctic sea-ice decline events
Publisher: Copernicus GmbH
Date: 26-02-2023
DOI: 10.5194/EGUSPHERE-EGU23-16112
Abstract: & & Antarctic sea-ice extent showed an unprecedented decline during 2015/16 after showing a weak positive trend since the last four decades. Many studies have attempted to understand the reasons behind this sudden decline in the sea-ice and have shown important influences from the atmosphere as well as the upper ocean processes. In this study, we attempt to understand similar sudden Antarctic sea-ice decline episodes in the long pre-industrial control simulations of multiple CMIP models. We examine the change in sea-ice extent from September to January and classify the events as sudden decline events based on the magnitude of this change. Composite analyses are then carried out to understand the similar atmospheric as well as oceanic processes as play during such events. Preliminary analyses suggest an important role of the Zonal wave 3 lification during September & #8211 November period similar to what was observed during 2016. We also notice a clear El-Nino signature in the tropical Pacific from the preceding austral summer with a presence of warm SSTs around Antarctica during the sea-ice growth season. More detailed analysis are currently being carried out and the results will be presented during the conference.& &
Pacific western boundary currents and their roles in climate
Publisher: Springer Science and Business Media LLC
Date: 06-2015
DOI: 10.1038/NATURE14504
Abstract: Pacific Ocean western boundary currents and the interlinked equatorial Pacific circulation system were among the first currents of these types to be explored by pioneering oceanographers. The widely accepted but poorly quantified importance of these currents-in processes such as the El Niño/Southern Oscillation, the Pacific Decadal Oscillation and the Indonesian Throughflow-has triggered renewed interest. Ongoing efforts are seeking to understand the heat and mass balances of the equatorial Pacific, and possible changes associated with greenhouse-gas-induced climate change. Only a concerted international effort will close the observational, theoretical and technical gaps currently limiting a robust answer to these elusive questions.
Projected Marine Heatwaves in the 21st Century and the Potential for Ecological Impact
Publisher: Frontiers Media SA
Date: 04-12-2019
On Challenges in Predicting Bottom Water Transport in the Southern Ocean
Publisher: American Meteorological Society
Date: 08-02-2012
DOI: 10.1175/JCLI-D-11-00040.1
Abstract: Changes in the Southern Ocean lower-limb overturning circulation are analyzed using a set of climate models. In agreement with some recently developed theoretical models, it is found that the overturning can be strongly affected by winds. In particular, the simulated strengthening of large-scale southward transport in the abyss is explicitly driven by zonal wind stress. However, there is a considerable range among the climate models in their projected changes of Southern Ocean wind stress. Furthermore, the strengthening of large-scale southward transport tends to be compensated by eddy-induced northward flows in the abyss, particularly at eddy-permitting resolution. As a result, the net Antarctic Bottom Water (AABW) export may only be weakly affected. However, none of the models considered accounts for the possibility that a fraction of the eddy kinetic energy may be converted to diapycnal mixing. If this were the case, the presented energetic arguments suggest that stronger Southern Ocean winds would result in a stronger AABW transport.
Historical and Projected Changes in the Southern Hemisphere Surface Westerlies
Publisher: American Geophysical Union (AGU)
Date: 22-02-2021
DOI: 10.1029/2020GL090849
Abstract: The Southern Hemisphere (SH) surface westerlies fundamentally control regional patterns of air temperature, storm tracks, and precipitation while also regulating ocean circulation, heat transport and carbon uptake. Wind‐forced ocean perturbation experiments commonly apply idealized poleward wind shifts ranging between 0.5 and 10 degrees of latitude and wind intensification factors of between 10% and 300%. In addition, changes in winds are often prescribed ad hoc as a zonally uniform anomaly that neglects important regional and seasonal differences. Here we quantify historical and projected SH westerly wind changes based on examination of CMIP5, CMIP6, and reanalysis data. We find a significant reduction in the location bias of the CMIP6 ensemble and an associated reduction in the projected poleward shift compared to CMIP5. Under a high emission scenario, we find a projected end of 21st Century ensemble mean wind increase of ∼10% and a poleward shift of ∼0.8° latitude, although there are important seasonal and regional variations.
Drier tropical and subtropical Southern Hemisphere in the mid-Pliocene Warm Period
Publisher: Springer Science and Business Media LLC
Date: 10-08-2002
DOI: 10.1038/S41598-020-68884-5
Abstract: Thermodynamic arguments imply that global mean rainfall increases in a warmer atmosphere however, dynamical effects may result in more significant ersity of regional precipitation change. Here we investigate rainfall changes in the mid-Pliocene Warm Period (~ 3 Ma), a time when temperatures were 2–3ºC warmer than the pre-industrial era, using output from the Pliocene Model Intercomparison Projects phases 1 and 2 and sensitivity climate model experiments. In the Mid-Pliocene simulations, the higher rates of warming in the northern hemisphere create an interhemispheric temperature gradient that enhances the southward cross-equatorial energy flux by up to 48%. This intensified energy flux reorganizes the atmospheric circulation leading to a northward shift of the Inter-Tropical Convergence Zone and a weakened and poleward displaced Southern Hemisphere Subtropical Convergences Zones. These changes result in drier-than-normal Southern Hemisphere tropics and subtropics. The evaluation of the mid-Pliocene adds a constraint to possible future warmer scenarios associated with differing rates of warming between hemispheres.
How did ocean warming affect Australian rainfall extremes during the 2010/2011 La Niña event?
Publisher: American Geophysical Union (AGU)
Date: 19-11-2015
DOI: 10.1002/2015GL065948
Coupled Ocean–Atmosphere–Ice Response to Variations in the Southern Annular Mode
Publisher: American Meteorological Society
Date: 15-09-2006
DOI: 10.1175/JCLI3843.1
Abstract: The coupled ocean–atmosphere–ice response to variations in the Southern Annular Mode (SAM) is examined in the National Center for Atmospheric Research (NCAR) Community Coupled Climate Model (version 2). The model shows considerable skill in capturing the predominantly zonally symmetric SAM while regional deviations between model and observation SAM winds go a long way in explaining the generally small differences between simulated and observed SAM responses in the ocean and sea ice systems. Vacillations in the position and strength of the circumpolar winds and the ensuing variations in advection of heat and moisture result in a dynamic and thermodynamic forcing of the ocean and sea ice. Both meridional and zonal components of ocean circulation are modified through Ekman transport, which in turn leads to anomalous surface convergences and ergences that strongly affect the meridional overturning circulation and potentially the pathways of intermediate water ventilation. A heat budget analysis demonstrates a conspiring of oceanic meridional heat advection, surface heat fluxes, and changes in mixed layer depth, which acts in phase to imprint a strong circumpolar SAM signature onto sea surface temperatures (SSTs), while other oceanic processes, including vertical advection, are shown to play only a minor role in contrast to previous suggestions. Lagged correlations show that although the SAM is mainly controlled by internal atmospheric mechanisms, the thermal inertia of the ocean reimprints the SAM signature back onto surface air temperatures (SATs) on time scales longer than the initial atmospheric signal. Sea ice variability is well explained by a combination of atmospheric and oceanic dynamic and thermodynamic forcing, and by an albedo feedback mechanism that allows ice extent anomalies to persist for many months. Nonzonally symmetric components of the SAM winds, particularly in the region surrounding the Antarctic Peninsula, have important effects for other climate variables.
Marine heatwaves threaten global biodiversity and the provision of ecosystem services
Publisher: Springer Science and Business Media LLC
Date: 04-03-2019
Variability in the origins and pathways of P acific E quatorial U ndercurrent water
Publisher: American Geophysical Union (AGU)
Date: 04-2015
DOI: 10.1002/2014JC010549
Abstract: The Pacific Equatorial Undercurrent (EUC) transports water originating from a number of distinct source regions, eastward across the Pacific Ocean. It is responsible for supplying nutrients to the productive eastern Equatorial Pacific Ocean. Of particular importance is the transport of iron by the EUC the limiting nutrient in that region. Although the mean circulation and sources of EUC water are reasonably well understood, it is unclear how the contribution of water from these sources to the EUC vary on seasonal to interannual timescales. Here a Lagrangian analysis is applied to the eddy‐resolving OFAM3 ocean simulation in order to identity variability in the makeup of the EUC over an 18 year period (1993–2010). While ENSO has an influence on the variability of source transport contributions to the EUC, the signal of increased (decreased) transport of water from the LLWBCs during El Niño (La Niña) periods does not translate to substantial changes in the makeup of the EUC between 165°E and 140°W. It is hypothesized that this is due to the large spread in travel times of water parcels as they travel from the source regions into the EUC. The consequent erosion of transport anomalies generated at the different western boundary source regions associated with ENSO may help explain why previous studies found little relationship between variability in iron fluxes off Papua New Guinea shelves and the chlorophyll response in the eastern tropical Pacific.
Projected Changes to the Southern Hemisphere Ocean and Sea Ice in the IPCC AR4 Climate Models
Publisher: American Meteorological Society
Date: 06-2009
Abstract: Fidelity and projected changes in the climate models, used for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), are assessed with regard to the Southern Hemisphere extratropical ocean and sea ice systems. While in idual models span different physical parameterizations and resolutions, a major component of intermodel variability results from surface wind differences. Projected changes to the surface wind field are also central in modifying future extratropical circulation and internal properties. A robust southward shift of the circumpolar current and subtropical gyres is projected, with a strong spinup of the Atlantic gyre. An associated increase in the core strength of the circumpolar circulation is evident however, this does not translate into robust increases in Drake Passage transport. While an overarching oceanic warming is projected, the circulation-driven poleward shift of the temperature field explains much of the midlatitude warming pattern. The effect of this shift is less clear for salinity, where, instead, surface freshwater forcing dominates. Surface warming and high-latitude freshwater increases drive intensified stratification, and a shoaling and southward shift of the deep mixed layers. Despite large intermodel differences, there is also a robust weakening in bottom water formation and its northward outflow. At the same time the wind intensification invigorates the upwelling of deep water, transporting warm, salty water southward and upward, with major implications for sequestration and outgassing of CO2. A robust decrease is projected for both the sea ice concentration and the seasonal cycling of ice volume, potentially altering the salt and heat budget at high latitudes.
Future Changes to El Niño–Southern Oscillation Temperature and Precipitation Teleconnections
Publisher: American Geophysical Union (AGU)
Date: 21-10-2017
DOI: 10.1002/2017GL074509
The tropicalization of temperate marine ecosystems: climate-mediated changes in herbivory and community phase shifts
Publisher: The Royal Society
Date: 22-08-2014
Abstract: Climate-driven changes in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species. In marine systems, changes in herbivory and the consequent loss of dominant habitat forming species can result in dramatic community phase shifts, such as from coral to macroalgal dominance when tropical fish herbivory decreases, and from algal forests to ‘barrens’ when temperate urchin grazing increases. Here, we propose a novel phase-shift away from macroalgal dominance caused by tropical herbivores extending their range into temperate regions. We argue that this phase shift is facilitated by poleward-flowing boundary currents that are creating ocean warming hotspots around the globe, enabling the range expansion of tropical species and increasing their grazing rates in temperate areas. Overgrazing of temperate macroalgae by tropical herbivorous fishes has already occurred in Japan and the Mediterranean. Emerging evidence suggests similar phenomena are occurring in other temperate regions, with increasing occurrence of tropical fishes on temperate reefs.
Climate Drift in the CMIP5 Models*
Publisher: American Meteorological Society
Date: 16-10-2013
DOI: 10.1175/JCLI-D-12-00521.1
Abstract: Climate models often exhibit spurious long-term changes independent of either internal variability or changes to external forcing. Such changes, referred to as model “drift,” may distort the estimate of forced change in transient climate simulations. The importance of drift is examined in comparison to historical trends over recent decades in the Coupled Model Intercomparison Project (CMIP). Comparison based on a selection of metrics suggests a significant overall reduction in the magnitude of drift from phase 3 of CMIP (CMIP3) to phase 5 of CMIP (CMIP5). The direction of both ocean and atmospheric drift is systematically biased in some models introducing statistically significant drift in globally averaged metrics. Nevertheless, for most models globally averaged drift remains weak compared to the associated forced trends and is often smaller than the difference between trends derived from different ensemble members or the error introduced by the aliasing of natural variability. An exception to this is metrics that include the deep ocean (e.g., steric sea level) where drift can dominate in forced simulations. In such circumstances drift must be corrected for using information from concurrent control experiments. Many CMIP5 models now include ocean biogeochemistry. Like physical models, biogeochemical models generally undergo long spinup integrations to minimize drift. Nevertheless, based on a limited subset of models, it is found that drift is an important consideration and must be accounted for. For properties or regions where drift is important, the drift correction method must be carefully considered. The use of a drift estimate based on the full control time series is recommended to minimize the contamination of the drift estimate by internal variability.
Drivers and impacts of the most extreme marine heatwave events
Publisher: Springer Science and Business Media LLC
Date: 09-11-2020
DOI: 10.1038/S41598-020-75445-3
Abstract: Prolonged high-temperature extreme events in the ocean, marine heatwaves, can have severe and long-lasting impacts on marine ecosystems, fisheries and associated services. This study applies a marine heatwave framework to analyse a global sea surface temperature product and identify the most extreme events, based on their intensity, duration and spatial extent. Many of these events have yet to be described in terms of their physical attributes, generation mechanisms, or ecological impacts. Our synthesis identifies commonalities between marine heatwave characteristics and seasonality, links to the El Niño-Southern Oscillation, triggering processes and impacts on ocean productivity. The most intense events preferentially occur in summer, when climatological oceanic mixed layers are shallow and winds are weak, but at a time preceding climatological maximum sea surface temperatures. Most subtropical extreme marine heatwaves were triggered by persistent atmospheric high-pressure systems and anomalously weak wind speeds, associated with increased insolation, and reduced ocean heat losses. Furthermore, the most extreme events tended to coincide with reduced chlorophyll- a concentration at low and mid-latitudes. Understanding the importance of the oceanic background state, local and remote drivers and the ocean productivity response from past events are critical steps toward improving predictions of future marine heatwaves and their impacts.
Drivers of decadal hiatus periods in the 20th and 21st centuries
Publisher: American Geophysical Union (AGU)
Date: 20-08-2010
DOI: 10.1002/2014GL060527
Cold Tongue and Warm Pool ENSO Events in CMIP5: Mean State and Future Projections
Publisher: American Meteorological Society
Date: 10-04-2014
DOI: 10.1175/JCLI-D-13-00437.1
Abstract: The representation of the El Niño–Southern Oscillation (ENSO) under historical forcing and future projections is analyzed in 34 models from the Coupled Model Intercomparison Project phase 5 (CMIP5). Most models realistically simulate the observed intensity and location of maximum sea surface temperature (SST) anomalies during ENSO events. However, there exist systematic biases in the westward extent of ENSO-related SST anomalies, driven by unrealistic westward displacement and enhancement of the equatorial wind stress in the western Pacific. Almost all CMIP5 models capture the observed asymmetry in magnitude between the warm and cold events (i.e., El Niños are stronger than La Niñas) and between the two types of El Niños: that is, cold tongue (CT) El Niños are stronger than warm pool (WP) El Niños. However, most models fail to reproduce the asymmetry between the two types of La Niñas, with CT stronger than WP events, which is opposite to observations. Most models capture the observed peak in ENSO litude around December however, the seasonal evolution of ENSO has a large range of behavior across the models. The CMIP5 models generally reproduce the duration of CT El Niños but have biases in the evolution of the other types of events. The evolution of WP El Niños suggests that the decay of this event occurs through heat content discharge in the models rather than the advection of SST via anomalous zonal currents, as seems to occur in observations. No consistent changes are seen across the models in the location and magnitude of maximum SST anomalies, frequency, or temporal evolution of these events in a warmer world.
CORRIGENDUM
Publisher: American Meteorological Society
Date: 15-07-2011
Drivers of the projected changes to the Pacific Ocean equatorial circulation
Publisher: American Geophysical Union (AGU)
Date: 05-2012
DOI: 10.1029/2012GL051447
Optimising fisheries management in relation to tuna catches in the western central Pacific Ocean: A review of research priorities and opportunities
Publisher: Elsevier BV
Date: 09-2015
Future changes to the Indonesian Throughflow and Pacific circulation: The differing role of wind and deep circulation changes
Publisher: American Geophysical Union (AGU)
Date: 28-02-2016
DOI: 10.1002/2016GL067757
The Impact of Interacting Climate Modes on East Australian Precipitation Moisture Sources
Publisher: American Meteorological Society
Date: 15-05-2022
Abstract: Modes of climate variability can drive significant changes to regional climate affecting extremes such as droughts, floods, and bushfires. The need to forecast these extremes and expected future increases in their intensity and frequency motivates a need to better understand the physical processes that connect climate modes to regional precipitation. Focusing on east Australia, where precipitation is driven by multiple interacting climate modes, this study provides a new perspective into the links between large-scale modes of climate variability and precipitation. Using a Lagrangian back-trajectory approach, we examine how El Niño–Southern Oscillation (ENSO) modifies the supply of evaporative moisture for precipitation, and how this is modulated by the Indian Ocean dipole (IOD) and southern annular mode (SAM). We demonstrate that La Niña modifies large-scale moisture transport together with local thermodynamic changes to facilitate local precipitation generation, whereas below-average precipitation during El Niño stems predominantly from increased regional subsidence. These dynamic–thermodynamic processes were often more pronounced during co-occurring La Niña/negative IOD and El Niño ositive IOD periods. As the SAM is less strongly correlated with ENSO, the impact of co-occurring ENSO and SAM largely depended on the state of ENSO. La Niña–related processes were exacerbated when combined with +SAM and d ened when combined with −SAM, and vice versa during El Niño. This new perspective on how interacting climate modes physically influence regional precipitation can help elucidate how model biases affect the simulation of Australian climate, facilitating model improvement and understanding of regional impacts from long-term changes in these modes. How climate modes modulate the oceanic and terrestrial sources of moisture for rainfall in east Australia is investigated. East Australia is wetter during La Niña because more moisture is transported into the region and is more easily turned into rainfall when it arrives, whereas drier conditions during El Niño are because local conditions inhibit the conversion of moisture into rainfall. Distant atmospheric changes over the Indian and Southern Oceans can intensify these changes. Our results can be used to better understand and predict the regional impact of long-term changes in these modes of climate variability, which are potentially altered under climate change.
Indian and Pacific Ocean Influences on Southeast Australian Drought and Soil Moisture
Publisher: American Meteorological Society
Date: 03-2010
Abstract: The relative influences of Indian and Pacific Ocean modes of variability on Australian rainfall and soil moisture are investigated for seasonal, interannual, and decadal time scales. For the period 1900–2006, observations, reanalysis products, and hindcasts of soil moisture during the cool season (June–October) are used to assess the impacts of El Niño–Southern Oscillation (ENSO) and the Indian Ocean dipole (IOD) on southeastern Australia and the Murray–Darling Basin, two regions that have recently suffered severe droughts. A distinct asymmetry is found in the impacts of the opposite phases of both ENSO and IOD on Australian rainfall and soil moisture. There are significant differences between the dominant drivers of drought at interannual and decadal time scales. On interannual time scales, both ENSO and the IOD modify southeastern Australian soil moisture, with the driest (wettest) conditions over the southeast and more broadly over large parts of Australia occurring during years when an El Niño and a positive IOD event (La Niña and a negative IOD event) co-occur. The atmospheric circulation associated with these responses is discussed. Lower-frequency variability over southeastern Australia, however, including multiyear drought periods, seems to be more robustly related to Indian Ocean temperatures than Pacific conditions. The frequencies of both positive and negative IOD events are significantly different during periods of prolonged drought compared to extended periods of “normal” rainfall. In contrast, the frequency of ENSO events remains largely unchanged during prolonged dry and wet periods. For the Murray–Darling Basin, there appears to be a significant influence by La Niña and both positive and negative IOD events. In particular, La Niña plays a much more prominent role than for more southern regions, especially on interannual time scales and during prolonged wet periods. For prolonged dry (wet) periods, positive IOD events also occur in unusually high (low) numbers.
Effect of anomalous warming in the central Pacific on the Australian monsoon
Publisher: American Geophysical Union (AGU)
Date: 06-2009
DOI: 10.1029/2009GL038416
Longer and more frequent marine heatwaves over the past century
Publisher: Springer Science and Business Media LLC
Date: 10-04-2018
DOI: 10.1038/S41467-018-03732-9
Abstract: Heatwaves are important climatic extremes in atmospheric and oceanic systems that can have devastating and long-term impacts on ecosystems, with subsequent socioeconomic consequences. Recent prominent marine heatwaves have attracted considerable scientific and public interest. Despite this, a comprehensive assessment of how these ocean temperature extremes have been changing globally is missing. Using a range of ocean temperature data including global records of daily satellite observations, daily in situ measurements and gridded monthly in situ-based data sets, we identify significant increases in marine heatwaves over the past century. We find that from 1925 to 2016, global average marine heatwave frequency and duration increased by 34% and 17%, respectively, resulting in a 54% increase in annual marine heatwave days globally. Importantly, these trends can largely be explained by increases in mean ocean temperatures, suggesting that we can expect further increases in marine heatwave days under continued global warming.
Corrigendum to ‘Multi-decadal projections of surface and interior pathways of the Fukushima Cesium-137 radioactive plume’ [Deep-Sea Research I 80 (2013) 37–46]
Publisher: Elsevier BV
Date: 12-2013
From severe droughts in South America to marine heatwaves in the South Atlantic
Publisher: Copernicus GmbH
Date: 07-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-5162
Abstract: & & In 2013/14 eastern South America experienced one of its worst droughts, leading to water shortages in S& #227 o Paulo, the world& #8217 s fourth most populated city. This event was also responsible for a dengue fever outbreak that tripled the usual number of fatalities and reduced Brazilian coffee production leading to a global shortages and worldwide price increases. The drought was associated with an anomalous anticyclonic circulation off southeast South America that prevented synoptic systems reaching the region while inhibiting the development of the South Atlantic Convergence Zone and its associated rainfall. A concomitant and unprecedented marine heatwave also developed in the southwest Atlantic. Here we show from observations that such droughts and adjacent marine heatwaves have a common remote cause. Atmospheric blocking triggered by tropical convection in the Indian and Pacific oceans can cause persistent anticyclonic circulation that not only leads to severe drought but also generates marine heatwaves in the adjacent ocean. We show that increased shortwave radiation due to reduced cloud cover and reduced ocean heat loss from weaker winds are the main contributors to the establishment of marine heatwaves in the region. The proposed mechanism, which involves droughts, extreme air temperature over land and atmospheric blocking explains approximately 60% of the marine heatwave events in the western South Atlantic. We also identified an increase in frequency, duration, intensity and extension of marine heatwave events over the satellite period 1982& #8211 . Moreover, surface primary production was reduced during these events with implications for regional fisheries.& &
Genesis of Indian Ocean Mixed Layer Temperature Anomalies: A Heat Budget Analysis
Publisher: American Meteorological Society
Date: 15-06-2010
Abstract: The genesis of mixed layer temperature anomalies across the Indian Ocean are analyzed in terms of the underlying heat budget components. Observational data, for which a seasonal budget can be computed, and a climate model output, which provides improved spatial and temporal coverage for longer time scales, are examined. The seasonal climatology of the model heat budget is broadly consistent with the observational reconstruction, thus providing certain confidence in extending the model analysis to interannual time scales. To identify the dominant heat budget components, covariance analysis is applied based on the heat budget equation. In addition, the role of the heat budget terms on the generation and decay of temperature anomalies is revealed via a novel temperature variance budget approach. The seasonal evolution of the mixed layer temperature is found to be largely controlled by air–sea heat fluxes, except in the tropics where advection and entrainment are important. A distinct shift in the importance and role of certain heat budget components is shown to be apparent in moving from seasonal to interannual time scales. On these longer time scales, advection gains importance in generating and sustaining anomalies over extensive regions, including the trade wind and midlatitude wind regimes. On the other hand, air–sea heat fluxes tend to drive the evolution of thermal anomalies over subtropical regions including off northwestern Australia. In the tropics, however, they limit the growth of anomalies. Entrainment plays a role in the generation and maintenance of interannual anomalies over localized regions, particularly off Sumatra and over the Seychelles–Chagos Thermocline Ridge. It is further shown that the spatial distribution of the role and importance of these terms is related to oceanographic features of the Indian Ocean. Mixed layer depth effects and the influence of model biases are discussed.
Generation of the Amundsen Sea Low by Antarctic Orography
Publisher: American Geophysical Union (AGU)
Date: 16-02-2021
DOI: 10.1029/2020GL091487
Abstract: The Amundsen Sea Low (ASL) is a distinctive feature of the Southern Hemisphere high latitude atmospheric circulation, regulating regional Antarctic climate, meridional heat transport, ocean circulation, and sea‐ice in the Amundsen‐Bellingshausen Seas. Most previous research on the ASL has focused on its variability with only a few studies attempting to understand why the climatological ASL exists. These studies have proposed different hypotheses to explain the presence of the ASL, however, a clear understanding of the mechanisms responsible for the generation of the ASL remains uncertain. Here we use an atmospheric general circulation model to show that the ASL is a consequence of the interaction between Antarctic topography and the westerly wind jet, with negligible influence from low‐latitude teleconnections. A nonrotating fluid flow simulation further suggests that the ASL can be explained by flow separation resulting from the interaction of westerly winds with the topography of Antarctica.
Zonal wave 3 pattern in the Southern Hemisphere generated by tropical convection
Publisher: Springer Science and Business Media LLC
Date: 26-08-2021
Keeping pace with marine heatwaves
Publisher: Springer Science and Business Media LLC
Date: 28-07-2001
Regional Versus Remote Atmosphere‐Ocean Drivers of the Rapid Projected Intensification of the East Australian Current
Publisher: American Geophysical Union (AGU)
Date: 07-2020
DOI: 10.1029/2019JC015889
Projected changes to South Atlantic boundary currents and confluence region in the CMIP5 models: the role of wind and deep ocean changes
Publisher: IOP Publishing
Date: 09-2016
Constraining future greenhouse gas emissions by a cumulative target
Publisher: Proceedings of the National Academy of Sciences
Date: 29-09-2009
Causes of Late Twentieth-Century Trends in New Zealand Precipitation
Publisher: American Meteorological Society
Date: 2009
Abstract: Late twentieth-century trends in New Zealand precipitation are examined using observations and reanalysis data for the period 1979–2006. One of the aims of this study is to investigate the link between these trends and recent changes in the large-scale atmospheric circulation in the Southern Hemisphere. The contributions from changes in Southern Hemisphere climate modes, particularly the El Niño–Southern Oscillation (ENSO) and the southern annular mode (SAM), are quantified for the austral summer season, December–February (DJF). Increasingly drier conditions over much of New Zealand can be partially explained by the SAM and ENSO. Especially over wide parts of the North Island and western regions of the South Island, the SAM potentially contributes up to 80% and 20%–50% to the overall decline in DJF precipitation, respectively. Over the North Island, the contribution of the SAM and ENSO to precipitation trends is of the same sign. In contrast, over the southwest of the South Island the two climate modes act in the opposite sense, though the effect of the SAM seems to dominate there during austral summer. The leading modes of variability in summertime precipitation over New Zealand are linked to the large-scale atmospheric circulation. The two dominant modes, explaining 64% and 9% of the overall DJF precipitation variability respectively, can be understood as local manifestations of the large-scale climate variability associated with the SAM and ENSO.
Multi-decadal projections of surface and interior pathways of the Fukushima Cesium-137 radioactive plume
Publisher: Elsevier BV
Date: 10-2013
What causes southeast Australia's worst droughts?
Publisher: American Geophysical Union (AGU)
Date: 02-2009
DOI: 10.1029/2008GL036801
Effects of volcanism on tropical variability
Publisher: American Geophysical Union (AGU)
Date: 25-07-2015
DOI: 10.1002/2015GL064751
Evaluating global climate models for the Pacific island region
Publisher: Inter-Research Science Center
Date: 20-10-2011
DOI: 10.3354/CR01028
An Assessment of Drift Correction Alternatives for CMIP5 Decadal Predictions
Publisher: American Geophysical Union (AGU)
Date: 14-10-2017
DOI: 10.1002/2017JD026900
Climate Drift in the CMIP3 Models
Publisher: American Meteorological Society
Date: 07-2012
DOI: 10.1175/JCLI-D-11-00312.1
Abstract: Even in the absence of external forcing, climate models often exhibit long-term trends that cannot be attributed to natural variability. This so-called climate drift arises for various reasons including the following: perturbations to the climate system on coupling component models together and deficiencies in model physics and numerics. When examining trends in historical or future climate simulations, it is important to know the error introduced by drift so that action can be taken where necessary. This study assesses the importance of drift for a number of climate properties at global and local scales. To illustrate this, the present paper focuses on simulated trends over the second half of the twentieth century. While drift in globally averaged surface properties is generally considerably smaller than observed and simulated twentieth-century trends, it can still introduce nontrivial errors in some models. Furthermore, errors become increasingly important at smaller scales. The direction of drift is not systematic across different models or variables, as such drift is considerably reduced in the multimodel mean. Despite drift being primarily associated with ocean adjustment, it is also apparent in atmospheric variables. For ex le, most models have local drift magnitudes in surface air and ocean temperatures that are typically between 15% and 35% of the twentieth-century simulation trend magnitudes for 1950–2000. Below depths of 1000–2000 m, drift dominates over any forced trend in most regions. As such steric sea level is strongly affected and for some models and regions the sea level trend direction is reversed. Thus depending on the application, drift may be negligible or may make up an important part of the simulated trend.
Iron sources and pathways into the Pacific Equatorial Undercurrent
Publisher: American Geophysical Union (AGU)
Date: 28-09-2016
DOI: 10.1002/2016GL070501
Pacific‐to‐Indian Ocean connectivity: Tasman leakage, Indonesian Throughflow, and the role of ENSO
Publisher: American Geophysical Union (AGU)
Date: 02-2014
DOI: 10.1002/2013JC009525
The National Marine Science Plan: informing Australia’s future ocean policy*
Publisher: Informa UK Limited
Date: 02-01-2016
Mixed responses of tropical Pacific fisheries and aquaculture to climate change
Publisher: Springer Science and Business Media LLC
Date: 10-03-2013
DOI: 10.1038/NCLIMATE1838
Demystifying global climate models for use in the life sciences
Publisher: Elsevier BV
Date: 09-2023
Marine biodiversity exposed to prolonged and intense subsurface heatwaves
Publisher: Springer Science and Business Media LLC
Date: 18-09-2023
Correction to: Role of Pacific trade winds in driving ocean temperatures during the recent slowdown and projections under a wind trend reversal
Publisher: Springer Science and Business Media LLC
Date: 18-05-2018
A global assessment of marine heatwaves and their drivers
Publisher: Springer Science and Business Media LLC
Date: 14-06-2019
DOI: 10.1038/S41467-019-10206-Z
Abstract: Marine heatwaves (MHWs) can cause devastating impacts to marine life. Despite the serious consequences of MHWs, our understanding of their drivers is largely based on isolated case studies rather than any systematic unifying assessment. Here we provide the first global assessment under a consistent framework by combining a confidence assessment of the historical refereed literature from 1950 to February 2016, together with the analysis of MHWs determined from daily satellite sea surface temperatures from 1982–2016, to identify the important local processes, large-scale climate modes and teleconnections that are associated with MHWs regionally. Clear patterns emerge, including coherent relationships between enhanced or suppressed MHW occurrences with the dominant climate modes across most regions of the globe – an important exception being western boundary current regions where reports of MHW events are few and ocean-climate relationships are complex. These results provide a global baseline for future MHW process and prediction studies.
Impacts of the tropical trans-basin variability on Australian rainfall
Publisher: Springer Science and Business Media LLC
Date: 22-10-2016
Historical and projected changes in the Southern Hemisphere surface westerlies
Publisher: Wiley
Date: 30-09-2020
Author Correction: Pathways to sustaining tuna-dependent Pacific Island economies during climate change
Publisher: Springer Science and Business Media LLC
Date: 16-06-2023
Future changes to the upper ocean Western Boundary Currents across two generations of climate models
Publisher: Springer Science and Business Media LLC
Date: 05-05-2021
DOI: 10.1038/S41598-021-88934-W
Abstract: Western Boundary Currents (WBCs) are important for the oceanic transport of heat, dissolved gases and nutrients. They can affect regional climate and strongly influence the dispersion and distribution of marine species. Using state-of-the-art climate models from the latest and previous Climate Model Intercomparison Projects , we evaluate upper ocean circulation and examine future projections, focusing on subtropical and low-latitude WBCs. Despite their coarse resolution, climate models successfully reproduce most large-scale circulation features with ensemble mean transports typically within the range of observational uncertainty, although there is often a large spread across the models and some currents are systematically too strong or weak. Despite considerable differences in model structure, resolution and parameterisations, many currents show highly consistent projected changes across the models. For ex le, the East Australian Current, Brazil Current and Agulhas Current extensions are projected to intensify, while the Gulf Stream, Indonesian Throughflow and Agulhas Current are projected to weaken. Intermodel differences in most future circulation changes can be explained in part by projected changes in the large-scale surface winds. In moving to the latest model generation, despite structural model advancements, we find little systematic improvement in the simulation of ocean transports nor major differences in the projected changes.
Tropical Pacific Observing System
Publisher: Frontiers Media SA
Date: 18-02-2019
Episodic and non-uniform shifts of thermal habitats in a warming ocean
Publisher: Elsevier BV
Date: 03-3000
Implications of CMIP3 model biases and uncertainties for climate projections in the western tropical Pacific
Publisher: Springer Science and Business Media LLC
Date: 09-11-2012
Uncertainty in near-term global surface warming linked to tropical Pacific climate variability
Publisher: Springer Science and Business Media LLC
Date: 30-04-2019
DOI: 10.1038/S41467-019-09761-2
Abstract: Climate models generally simulate a long-term slowdown of the Pacific Walker Circulation in a warming world. However, despite increasing greenhouse forcing, there was an unprecedented intensification of the Pacific Trade Winds during 1992–2011, that co-occurred with a temporary slowdown in global surface warming. Using ensemble simulations from three different climate models starting from different initial conditions, we find a large spread in projected 20-year globally averaged surface air temperature trends that can be linked to differences in Pacific climate variability. This implies diminished predictive skill for global surface air temperature trends over decadal timescales, to a large extent due to intrinsic Pacific Ocean variability. We show, however, that this uncertainty can be considerably reduced when the initial oceanic state is known and well represented in the model. In this case, the spatial patterns of 20-year surface air temperature trends depend largely on the initial state of the Pacific Ocean.
The Modulation of ENSO Variability in CCSM3 by Extratropical Rossby Waves
Publisher: American Meteorological Society
Date: 15-11-2009
Abstract: Evidence suggests that the magnitude and frequency of the El Niño–Southern Oscillation (ENSO) changes on interdecadal time scales. This is manifest in a distinct shift in ENSO behavior during the late 1970s. This study investigates mechanisms that may force this interdecadal variability and, in particular, on modulations driven by extratropical Rossby waves. Results from oceanic shallow-water models show that the Rossby wave theory can explain small near-zonal changes in equatorial thermocline depth that can alter the litude of simulated ENSO events. However, questions remain over whether the same mechanism operates in more complex coupled general circulation models (CGCMs) and what the magnitude of the resulting change would be. Experiments carried out in a state-of-the-art z-coordinate primitive equation model confirm that the Rossby wave mechanism does indeed operate. The effects of these interactions are further investigated using a partial coupling (PC) technique. This allows for the isolation of the role of wind stress–forced oceanic exchanges between the extratropics and the tropics and the subsequent modulation of ENSO variability. It is found that changes in the background state of the equatorial Pacific thermocline depth, induced by a fixed off-equatorial wind stress anomaly, can significantly affect the probability of ENSO events occurring. This confirms the results obtained from simpler models and further validates theories that rely on oceanic wave dynamics to generate Pacific Ocean interdecadal variability. This indicates that an improved predictive capability for seasonal-to-interannual ENSO variability could be achieved through a better understanding of extratropical-to-tropical Pacific Ocean transfers and western boundary processes. Furthermore, such an understanding would provide a physical basis to enhance multiyear probabilistic predictions of ENSO indices.
Common cause for severe droughts in South America and marine heatwaves in the South Atlantic
Publisher: Springer Science and Business Media LLC
Date: 08-07-2019
Coupled Ocean–Atmosphere Feedback in the Southern Annular Mode
Publisher: American Meteorological Society
Date: 15-07-2007
DOI: 10.1175/JCLI4200.1
Abstract: Previous studies have demonstrated that while the Southern Annular Mode (SAM) is an intrinsic feature of the atmosphere, it projects strongly onto the ocean and sea ice properties and circulation. This study investigates the extent of “back interaction” whereby these oceanic SAM anomalies feed back to the atmosphere. A comparison between atmosphere-only and full coupled climate models demonstrates that air–sea interactions in the coupled system act to increase the persistence of the SAM in the atmosphere. To identify the nature of feedback from the ocean to the atmosphere, ensemble experiments are carried out in both atmosphere-only and full coupled models whereby a continuous SAM-like sea surface temperature (SST) anomaly is imposed. Both coupled and uncoupled experiments show a direct thermal response that affects the lower-tropospheric temperature and surface meridional winds. An indirect upper troposphere–wide response is also seen whose characteristics are sensitive to the coupling. For the uncoupled experiment a negative-phase SAM SST perturbation produces an indirect atmospheric response that projects strongly onto the SAM. A positive-phase anomaly, however, shows little robust response away from the local heating at the surface. The coupled experiments, however, do show linearity with respect to the sign of the anomaly. However, the response is considerably weaker than the uncoupled case and the projection of the response onto the SAM mode is poorer. Nonetheless the authors find a clear persistence of the SAM at interseasonal time scales that relies on air–sea coupling and cannot be reproduced in unforced atmosphere-only experiments. This demonstrates that the ocean plays a role in modulating the Southern Annular Mode at these time scales.
Pathways to sustaining tuna-dependent Pacific Island economies during climate change
Publisher: Springer Science and Business Media LLC
Date: 29-07-2021
DOI: 10.1038/S41893-021-00745-Z
Abstract: Climate-driven redistribution of tuna threatens to disrupt the economies of Pacific Small Island Developing States (SIDS) and sustainable management of the world’s largest tuna fishery. Here we show that by 2050, under a high greenhouse gas emissions scenario (RCP 8.5), the total biomass of three tuna species in the waters of ten Pacific SIDS could decline by an average of 13% (range = −5% to −20%) due to a greater proportion of fish occurring in the high seas. The potential implications for Pacific Island economies in 2050 include an average decline in purse-seine catch of 20% (range = −10% to −30%), an average annual loss in regional tuna-fishing access fees of US$90 million (range = −US$40 million to –US$140 million) and reductions in government revenue of up to 13% (range = −8% to −17%) for in idual Pacific SIDS. Redistribution of tuna under a lower-emissions scenario (RCP 4.5) is projected to reduce the purse-seine catch from the waters of Pacific SIDS by an average of only 3% (range = −12% to +9%), indicating that even greater reductions in greenhouse gas emissions, in line with the Paris Agreement, would provide a pathway to sustainability for tuna-dependent Pacific Island economies. An additional pathway involves Pacific SIDS negotiating within the regional fisheries management organization to maintain the present-day benefits they receive from tuna, regardless of the effects of climate change on the distribution of the fish.
Generation of the Amundsen Sea Low by Antarctic orography
Publisher: Wiley
Date: 02-11-2020
Constraining Wind Stress Products with Sea Surface Height Observations and Implications for Pacific Ocean Sea Level Trend Attribution*
Publisher: American Meteorological Society
Date: 12-2012
DOI: 10.1175/JCLI-D-12-00105.1
Abstract: A number of global surface wind datasets are available that are commonly used to examine climate variability or trends and as boundary conditions for ocean circulation models. However, discrepancies exist among these products. This study uses observed Archiving, Validation, and Interpretation of Satellite Oceanographic (AVISO) sea surface height anomalies (SSHAs) as a means to help constrain the fidelity of these products in the tropical region. Each wind stress product is used to force a linear shallow water model (SWM) and the resulting hindcast thermocline depth anomalies are converted to SSHAs. The resulting SSHAs are then assessed to see how well they reproduce the dominant EOF modes of observed variability and the regional (global mean removed) sea level trend (1993–2007) in each of the three ocean basins. While the results suggest that all wind datasets reproduce the observed interannual variability with reasonable fidelity, the two SWM hindcasts that produce the observed linear trend with the highest fidelity are those incorporating interim ECMWF Re-Analysis (ERA-Interim) and Wave- and Anemometer-Based Sea Surface Wind (WASWind) forcing. The role of surface wind forcing (i.e., upper ocean heat content redistribution) versus global mean sea level change (i.e., including the additional contributions of glacier and ice sheet melt along with ocean thermal expansion) on the recent dramatic increase in western equatorial Pacific island sea level is then reassessed. The results suggest that the recent sea level increase cannot be explained solely by wind stress forcing, regardless of the dataset used rather, the global mean sea level signal is required to fully explain this observed recent abrupt sea level rise and to better explain the sea level variability of the last 50–60 years.
Sampling biases in CMIP5 decadal forecasts
Publisher: American Geophysical Union (AGU)
Date: 14-04-2016
DOI: 10.1002/2016JD024804
Effectiveness of CMIP5 Decadal Experiments for Interannual Rainfall Prediction Over Australia
Publisher: American Geophysical Union (AGU)
Date: 08-2019
DOI: 10.1029/2018WR024462
Mid-Pliocene El Niño/Southern Oscillation suppressed by Pacific intertropical convergence zone shift
Publisher: Springer Science and Business Media LLC
Date: 11-08-2022
On the predictability of SSTA indices from CMIP5 decadal experiments
Publisher: IOP Publishing
Date: 07-2015
Coupled biophysical global ocean model and molecular genetic analyses identify multiple introductions of cryptogenic species
Publisher: Proceedings of the National Academy of Sciences
Date: 15-08-2005
Abstract: The anthropogenic introduction of exotic species is one of the greatest modern threats to marine bio ersity. Yet exotic species introductions remain difficult to predict and are easily misunderstood because knowledge of natural dispersal patterns, species ersity, and biogeography is often insufficient to distinguish between a broadly dispersed natural population and an exotic one. Here we compare a global molecular phylogeny of a representative marine meroplanktonic taxon, the moon-jellyfish Aurelia , with natural dispersion patterns predicted by a global biophysical ocean model. Despite assumed high dispersal ability, the phylogeny reveals many cryptic species and predominantly regional structure with one notable exception: the globally distributed Aurelia sp.1, which, molecular data suggest, may occasionally traverse the Pacific unaided. This possibility is refuted by the ocean model, which shows much more limited dispersion and patterns of distribution broadly consistent with modern biogeographic zones, thus identifying multiple introductions worldwide of this cryptogenic species. This approach also supports existing evidence that ( i ) the occurrence in Hawaii of Aurelia sp. 4 and other native Indo-West Pacific species with similar life histories is most likely due to anthropogenic translocation, and ( ii ) there may be a route for rare natural colonization of northeast North America by the European marine snail Littorina littorea , whose status as endemic or exotic is unclear.
Can Australian Multiyear Droughts and Wet Spells Be Generated in the Absence of Oceanic Variability?
Publisher: American Meteorological Society
Date: 19-08-2016
Abstract: Anomalous conditions in the tropical oceans, such as those related to El Niño–Southern Oscillation and the Indian Ocean dipole, have been previously blamed for extended droughts and wet periods in Australia. Yet the extent to which Australian wet and dry spells can be driven by internal atmospheric variability remains unclear. Natural variability experiments are examined to determine whether prolonged extreme wet and dry periods can arise from internal atmospheric and land variability alone. Results reveal that this is indeed the case however, these dry and wet events are found to be less severe than in simulations incorporating coupled oceanic variability. Overall, ocean feedback processes increase the magnitude of Australian rainfall variability by about 30% and give rise to more spatially coherent rainfall impacts. Over mainland Australia, ocean interactions lead to more frequent extreme events, particularly during the rainy season. Over Tasmania, in contrast, ocean–atmosphere coupling increases mean rainfall throughout the year. While ocean variability makes Australian rainfall anomalies more severe, droughts and wet spells of duration longer than three years are equally likely to occur in both atmospheric- and ocean-driven simulations. Moreover, they are essentially indistinguishable from what one expects from a Gaussian white noise distribution. Internal atmosphere–land-driven megadroughts and megapluvials that last as long as ocean-driven events are also identified in the simulations. This suggests that oceanic variability may be less important than previously assumed for the long-term persistence of Australian rainfall anomalies. This poses a challenge to accurate prediction of long-term dry and wet spells for Australia.
Assessment of the CMIP5 global climate model simulations of the western tropical Pacific climate system and comparison to CMIP3
Publisher: Wiley
Date: 07-02-2014
DOI: 10.1002/JOC.3916
Projected changes in the tropical Pacific Ocean of importance to tuna fisheries
Publisher: Springer Science and Business Media LLC
Date: 21-11-2012
Exploring Potential Links Between Co-occurring Coastal Terrestrial and Marine Heatwaves in Australia
Publisher: Frontiers Media SA
Date: 16-03-2022
DOI: 10.3389/FCLIM.2022.792730
Abstract: Despite numerous studies examining terrestrial or marine heatwaves independently, little work has investigated potential associations between these two types of extreme events. Examination of a limited number of past events suggests that certain co-occurring terrestrial and marine heatwaves have common drivers. Co-occurring events may also interact via local land-sea interactions, thereby altering the likelihood of these events. This study explores possible links between adjacent coastal marine and terrestrial heatwaves around Australia using observation and reanalysis data. We find a significant increase in the number of terrestrial heatwave days in the presence of an adjacent co-occurring marine heatwave along the coastal belt of Australia. In most regions, this increase persists at least 150 km inland. This suggests that processes operating beyond the narrow coastal belt are important in most regions. We also show that synoptic conditions driving a terrestrial heatwave in three locations around Australia are conducive for warming the ocean, which would increase the likelihood of a marine heatwave occurring. However, ocean state must also be conducive to reach MHW conditions. Our findings suggest that co-occurring terrestrial and marine heatwaves co-occur more frequently than chance would dictate, and that large scale synoptics may be conducive to both coastal terrestrial and marine heatwaves.
Factors influencing the skill of synthesized satellite wind products in the tropical Pacific
Publisher: American Geophysical Union (AGU)
Date: 02-2017
DOI: 10.1002/2016JC012340
Global Perspectives on Observing Ocean Boundary Current Systems
Publisher: Frontiers Media SA
Date: 08-08-2019
The Indo-Australian monsoon and its relationship to ENSO and IOD in reanalysis data and the CMIP3/CMIP5 simulations
Publisher: Springer Science and Business Media LLC
Date: 05-02-2013
Modulation of Australian Precipitation by Meridional Gradients in East Indian Ocean Sea Surface Temperature
Publisher: American Meteorological Society
Date: 11-2009
Abstract: This study explores the impact of meridional sea surface temperature (SST) gradients across the eastern Indian Ocean on interannual variations in Australian precipitation. Atmospheric general circulation model (AGCM) experiments are conducted in which the sign and magnitude of eastern Indian Ocean SST gradients are perturbed. This results in significant rainfall changes for western and southeastern Australia. A reduction (increase) in the meridional SST gradient drives a corresponding response in the atmospheric thickness gradients and results in anomalous dry (wet) conditions over Australia. During simulated wet years, this seems to be due to westerly anomalies in the thermal wind over Australia and anomalous onshore moisture advection, with a suggestion that the opposite occurs during dry conditions. Thus, an asymmetry is seen in the magnitude of the forced circulation and precipitation response between the dry and wet simulations. To assess the relative contribution of the SST anomalies making up the meridional gradient, the SST pattern is decomposed into its constituent “poles,” that is, the eastern tropical pole off the northwest shelf of Australia versus the southern pole in the central subtropical Indian Ocean. Overall, the simulated Australian rainfall response is linear with regard to the sign and magnitude of the eastern Indian Ocean SST gradient. The tropical eastern pole has a larger impact on the atmospheric circulation and Australian precipitation changes relative to the southern subtropical pole. However, there is clear evidence of the importance of the southern pole in enhancing the Australian rainfall response, when occurring in conjunction with but of opposite sign to the eastern tropical pole. The observed relationship between the meridional SST gradient in the eastern Indian Ocean and rainfall over western and southeastern Australia is also analyzed for the period 1970–2005. The observed relationship is found to be consistent with the AGCM results.
A hierarchical approach to defining marine heatwaves
Publisher: Elsevier BV
Date: 02-2016
Assessing the role of the ocean–atmosphere coupling frequency in the western Maritime Continent rainfall
Publisher: Springer Science and Business Media LLC
Date: 29-04-2020
Localising terrestrially derived pollution inputs to threatened near-shore coral reefs through stable isotope, water quality and oceanographic analysis
Publisher: Elsevier BV
Date: 08-2023
Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus
Publisher: Springer Science and Business Media LLC
Date: 09-02-2014
DOI: 10.1038/NCLIMATE2106
Response of Southern Hemisphere Western Boundary Current Regions to Future Zonally Symmetric and Asymmetric Atmospheric Changes
Publisher: American Geophysical Union (AGU)
Date: 11-2021
DOI: 10.1029/2021JC017858
Abstract: Subtropical western boundary currents (WBCs) are often associated with hotspots of global warming, with certain WBC extension regions warming 3–4 times faster than the global mean. In the Southern Hemisphere, strong warming over the WBC extensions has been observed over the last few decades, with enhanced warming projected into the future. This lified warming has primarily been linked to poleward intensification of the mid‐latitude westerly winds in the Southern Hemisphere. Changes in these winds are often thought of as being zonally symmetric however, recent studies show that they contain strong zonal asymmetries in certain ocean basins. The importance of these zonal asymmetries for the Southern Ocean has not yet been investigated. In this study, we use an ocean‐sea‐ice model forced by prescribed atmospheric fields to quantify the contribution of projected zonally asymmetric atmospheric changes in generating future ocean warming and circulation changes in the subtropical WBC regions. We find that the zonally asymmetric component of atmospheric forcing, characterized by a pattern that is consistent across CMIP6 models, can explain more than 30% ( °C) of the sea surface temperature (SST) warming found in the Tasman Sea and southern Australia region and a sizable fraction of warming in the Agulhas Current region. These changes in SST in both the Indian and Pacific basins are found to be primarily driven by increases in the advection of warm tropical water to the mid‐latitudes due to changes in the large‐scale subtropical ocean gyres, which in turn can largely be explained by changes in the mid‐latitude surface wind stress patterns.
Coral bleaching pathways under the control of regional temperature variability
Publisher: Springer Science and Business Media LLC
Date: 02-10-2017
DOI: 10.1038/NCLIMATE3399
Connections of climate change and variability to large and extreme forest fires in southeast Australia
Publisher: Springer Science and Business Media LLC
Date: 07-01-2021
DOI: 10.1038/S43247-020-00065-8
Abstract: The 2019/20 Black Summer bushfire disaster in southeast Australia was unprecedented: the extensive area of forest burnt, the radiative power of the fires, and the extraordinary number of fires that developed into extreme pyroconvective events were all unmatched in the historical record. Australia’s hottest and driest year on record, 2019, was characterised by exceptionally dry fuel loads that primed the landscape to burn when exposed to dangerous fire weather and ignition. The combination of climate variability and long-term climate trends generated the climate extremes experienced in 2019, and the compounding effects of two or more modes of climate variability in their fire-promoting phases (as occurred in 2019) has historically increased the chances of large forest fires occurring in southeast Australia. Palaeoclimate evidence also demonstrates that fire-promoting phases of tropical Pacific and Indian ocean variability are now unusually frequent compared with natural variability in pre-industrial times. Indicators of forest fire danger in southeast Australia have already emerged outside of the range of historical experience, suggesting that projections made more than a decade ago that increases in climate-driven fire risk would be detectable by 2020, have indeed eventuated. The multiple climate change contributors to fire risk in southeast Australia, as well as the observed non-linear escalation of fire extent and intensity, raise the likelihood that fire events may continue to rapidly intensify in the future. Improving local and national adaptation measures while also pursuing ambitious global climate change mitigation efforts would provide the best strategy for limiting further increases in fire risk in southeast Australia.
Pacific Equatorial Undercurrent: Mean state, sources, and future changes across models
Publisher: Frontiers Media SA
Date: 27-10-2012
DOI: 10.3389/FCLIM.2022.933091
Abstract: The Equatorial Undercurrent (EUC) stretches across the Pacific, transporting cool waters rich in oxygen and nutrients eastward to one of the most productive regions in the ocean. As an intricate part of the global climate system, EUC dynamics are essential to understanding future climate change but are poorly represented in global coupled climate models. This study examines EUC representation and future changes in the latest generations of the Coupled Model Intercomparison Project (CMIP6 and CMIP5) and an eddy-permitting ocean model. We also examine historical and projected changes in EUC source waters, including the Mindanao Current (MC), New Guinea Coastal Undercurrent (NGCU), and interior thermocline convergence. The circulation features in the models are broadly consistent with observations and ocean reanalyses, but improvements from CMIP5 to CMIP6 are limited. In the future projections, the EUC is enhanced in the western Pacific, with less prominent changes in CMIP6, but more so in the eddy-permitting model. The western Pacific EUC enhancement is likely associated with a wind-driven redirection of waters south of the equator, in which the NGCU boundary flow increases while the interior thermocline convergence decreases. This is superimposed on an overall weakening of the North Pacific subtropical overturning cell, including the MC, interior thermocline convergence, and Ekman ergence. As EUC heat and nutrient composition is linked to its sources, these projected changes have implications for the EUC's role in air–sea feedbacks, nutrient replenishment, and oxygen minimum zone ventilation in the eastern Pacific.
East Australian cyclones and air-sea feedbacks
Publisher: Wiley
Date: 18-01-2021
ENSO‐Driven Ocean Extremes and Their Ecosystem Impacts
Publisher: Wiley
Date: 23-10-2020
Contributions of Indian Ocean Sea Surface Temperatures to Enhanced East African Rainfall
Publisher: American Meteorological Society
Date: 15-02-2009
Abstract: Links between extreme wet conditions over East Africa and Indian Ocean sea surface temperatures (SST) are investigated during the core of the so-called short rain season in October–November. During periods of enhanced East African rainfall, Indian Ocean SST anomalies reminiscent of a tropical Indian Ocean dipole (IOD) event are observed. Ensemble simulations with an atmospheric general circulation model are used to understand the relative effect of local and large-scale Indian Ocean SST anomalies on above-average East African precipitation. The importance of the various tropical and subtropical IOD SST poles, both in idually and in combination, is quantified. In the simulations, enhanced East African “short rains” are predominantly driven by the local warm SST anomalies in the western equatorial Indian Ocean, while the eastern cold pole of the tropical IOD is of lesser importance. The changed East African rainfall distribution can be explained by a reorganization of the atmospheric circulation induced by the SST anomalies. A reduction in sea level pressure over the western half of the Indian Ocean and converging wind anomalies over East Africa lead to moisture convergence and increased convective activity over the region. The pattern of large-scale circulation changes over the tropical Indian Ocean and adjacent landmasses is consistent with an anomalous strengthening of the Walker cell. The seasonal cycle of various indices related to the SST and the atmospheric circulation in the equatorial Indian Ocean are examined to assess their potential usefulness for seasonal forecasting.
Can We Constrain CMIP5 Rainfall Projections in the Tropical Pacific Based on Surface Warming Patterns?*
Publisher: American Meteorological Society
Date: 10-12-2014
DOI: 10.1175/JCLI-D-14-00190.1
Abstract: Climate warming has large implications for rainfall patterns, and identifying the most plausible pattern of rainfall change over the next century among various model projections would be valuable for future planning. The spatial pattern of projected sea surface temperature change has a key influence on rainfall changes in the tropical Pacific Ocean. Here it is shown that simple indices of the size of the equatorial peak in the spatial pattern of warming and to a lesser extent the hemispheric asymmetry in warming are useful for classifying the surface temperature change in different models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). Models with a more pronounced equatorial warming show a fairly distinct rainfall response compared to those with more uniform warming, including a greater “warmer-get-wetter” or dynamical response, whereby rainfall increases follow the surface warming anomaly. Models with a more uniform warming pattern project a smaller rainfall increase at the equator and a rainfall increase in the southern tropical Pacific, a pattern that is distinct from the multimodel mean of CMIP5. Thus, the magnitude of enhanced equatorial warming and to some extent the hemispheric asymmetry in warming provides a useful framework for constraining rainfall projections. While there is not a simple emergent constraint for enhanced equatorial warming in models in terms of past trends or bias in the current climate, further understanding of the various feedbacks involved in these features could lead to a useful constraint of rainfall for the Pacific region.
A multimodel investigation of atmospheric mechanisms for driving Arctic amplification in warmer climates
Publisher: American Meteorological Society
Date: 17-05-2021
Abstract: When simulating past warm climates, such as the early Cretaceous and Paleogene periods, general circulation models (GCMs) underestimate the magnitude of warming in the Arctic. Additionally, model intercomparisons show a large spread in the magnitude of Arctic warming for these warmer-than-modern climates. Several mechanisms have been proposed to explain these disagreements, including the unrealistic representation of polar clouds or underestimated poleward heat transport in the models. This study provides an intercomparison of Arctic cloud and atmospheric heat transport (AHT) responses to strong imposed polar- lified surface ocean warming across four atmosphere-only GCMs. All models simulate an increase in high clouds throughout the year the resulting reduction in longwave radiation loss to space acts to support the imposed Arctic warming. The response of low and mid-level clouds varies considerably across the models, with models responding differently to surface warming and sea ice removal. The AHT is consistently weaker in the imposed warming experiments due to a large reduction in dry static energy transport that offsets a smaller increase in latent heat transport, thereby opposing the imposed surface warming. Our idealised polar lification experiments require very large increases in implied ocean heat transport (OHT) to maintain steady state. Increased CO 2 or tropical temperatures that likely characterised past warm climates, reduces the need for such large OHT increases.
Seasonal stratification and complex local dynamics control the sub-surface structure of marine heatwaves in Eastern Australian coastal waters
Publisher: Springer Science and Business Media LLC
Date: 09-2023
Projected Changes to Australian Marine Heatwaves
Publisher: American Geophysical Union (AGU)
Date: 30-03-2021
DOI: 10.1029/2020GL091323
Abstract: Marine heatwaves are extreme oceanic events that can have severe impacts on ecosystems and economies. Recent studies have suggested future increases in the severity and duration of these events. However, these findings are based on coarse resolution climate models that cannot resolve important ocean structures. This study uses a 0.25° coupled regional model to quantify how marine heatwaves around Australia respond under a high emissions scenario. We find that increases to future marine heatwave statistics are primarily caused by changes in the mean temperature, with changes in variability important in some areas. Temperature variance changes are most prominent close to Tasmania, with a covariance temperature budget demonstrating that this is linked to large simulated increases in East Australian Current transport and variability. Close to New Zealand, changes in surface heat fluxes also play an important role. These results quantify the response of marine heatwave characteristics to future temperature changes.
Association of Disease‐Specific Health Status With Long‐Term Survival in Peripheral Artery Disease
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 15-02-2022
Abstract: While peripheral artery disease (PAD) is associated with increased cardiovascular morbidity with mortality remaining high and challenging to predict, accurate understanding of serial PAD‐specific health status around the time of diagnosis may prognosticate long‐term mortality risk. Patients with new or worsening PAD symptoms enrolled in the PORTRAIT Registry across 10 US sites from 2011 to 2015 were included. Health status was assessed by the Peripheral Artery Questionnaire (PAQ) Summary score at baseline, 3‐month, and change from baseline to 3‐month follow‐up. Kaplan‐Meier using 3‐month landmark and hierarchical Cox regression models were constructed to assess the association of the PAQ with 5‐year all‐cause mortality. Of the 711 patients (mean age 68.8±9.6 years, 40.9% female, 72.7% white mean PAQ 47.5±22.0 and 65.9±25.0 at baseline and 3‐month, respectively), 141 (19.8%) died over a median follow‐up of 4.1 years. In unadjusted models, baseline (HR, 0.90 per‐10‐point increment 95% CI, 0.84–0.97 P =0.008), 3‐month (HR [95% CI], 0.87 [0.82–0.93] P .001) and change in PAQ (HR [95% CI], 0.92 [0.85–0.99] P =0.021) were each associated with mortality. In fully adjusted models including combination of scores, 3‐month PAQ was more strongly associated with mortality than either baseline (3‐month HR [95% CI], 0.85 [0.78–0.92] P .001 C‐statistic, 0.77) or change (3‐month HR [95% CI], 0.79 [0.72–0.87] P .001). PAD‐specific health status is independently associated with 5‐year survival in patients with new or worsening PAD symptoms, with the most recent assessment being most prognostic. Future work is needed to better understand how this information can be used proactively to optimize care.
Zonal Wave 3 Pattern in the Southern Hemisphere generated by tropical convection
Publisher: Research Square Platform LLC
Date: 17-03-2021
DOI: 10.21203/RS.3.RS-320008/V1
Abstract: A distinctive feature of the Southern Hemisphere (SH) extratropical atmospheric circulation is the quasi-stationary zonal wave 3 (ZW3) pattern, characterized by three high and three low-pressure centers around the SH extratropics. This feature is present in both the mean atmospheric circulation and its variability on daily, seasonal and interannual timescales. While the ZW3 pattern has significant impacts on meridional heat transport and Antarctic sea ice extent, the reason for its existence remains uncertain, although it has long been assumed to be linked to the existence of three major land masses in the SH extratropics. Here we use an atmospheric general circulation model to show that the stationery ZW3 pattern is instead driven by zonal asymmetric deep atmospheric convection in the tropics, with little to no role played by the orography or land masses in the extratropics. Localized regions of deep convection in the tropics form a local Hadley cell which in turn creates a wave source in the subtropics that excites a poleward and eastward propagating wave train which forms stationary waves in the SH high latitudes. Our findings suggest that changes in tropical deep convection, either due to natural variability or climate change, will impact the zonal wave 3 pattern, with implications for Southern Hemisphere climate, ocean circulation, and sea-ice.
Anomalous Rainfall over Southwest Western Australia Forced by Indian Ocean Sea Surface Temperatures
Publisher: American Meteorological Society
Date: 10-2008
Abstract: The potential impact of Indian Ocean sea surface temperature (SST) anomalies in modulating midlatitude precipitation across southern and western regions of Australia is assessed in a series of atmospheric general circulation model (AGCM) simulations. Two sets of AGCM integrations forced with a seasonally evolving characteristic dipole pattern in Indian Ocean SST consistent with observed “dry year” (PDRY) and “wet year” (PWET) signatures are shown to induce precipitation changes across western regions of Australia. Over Western Australia, a significant shift occurs in the winter and annual rainfall frequency with the distribution becoming skewed toward less (more) rainfall for the PDRY (PWET) SST pattern. For southwest Western Australia (SWWA), this shift primarily is due to the large-scale stable precipitation. Convective precipitation actually increases in the PDRY case over SWWA forced by local positive SST anomalies. A mechanism for the large-scale rainfall shifts is proposed, by which the SST anomalies induce a reorganization of the large-scale atmospheric circulation across the Indian Ocean basin. Thickness (1000–500 hPa) anomalies develop in the atmosphere mirroring the sign and position of the underlying SST anomalies. This leads to a weakening (strengthening) of the meridional thickness gradient and the subtropical jet during the austral winter in PDRY (PWET). The subsequent easterly offshore (westerly onshore) anomaly in the thermal wind over southern regions of Australia, along with a decrease (increase) in baroclinicity, results in the lower (higher) levels of large-scale stable precipitation. Variations in the vertical thermal structure of the atmosphere overlying the SST anomalies favor localized increased convective activity in PDRY because of differential temperature lapse rates. In contrast, enhanced widespread ascent of moist air masses associated with frontal movement in PWET accounts for a significant increase in rainfall in that ensemble set.
Quantification of errors induced by temporal resolution on Lagrangian particles in an eddy-resolving model
Publisher: Elsevier BV
Date: 04-2014
Resolution dependence of the simulated precipitation and diurnal cycle over the Maritime Continent
Publisher: Springer Science and Business Media LLC
Date: 19-08-2016
Exploring qualitative regional climate projections: a case study for Nauru
Publisher: Inter-Research Science Center
Date: 09-12-2013
DOI: 10.3354/CR01190
East Australian Cyclones and Air‐Sea Feedbacks
Publisher: American Geophysical Union (AGU)
Date: 15-10-2021
DOI: 10.1029/2020JD034391
Abstract: The importance of resolving mesoscale air‐sea interactions to represent cyclones impacting the East Coast of Australia, the so‐called East Coast Lows (ECLs), is investigated using the Australian Regional Coupled Model based on NEMO‐OASIS‐WRF (NOW) at resolution. The fully coupled model is shown to be capable of reproducing correctly relevant features such as the seasonality, spatial distribution and intensity of ECLs while it partially resolves mesoscale processes, such as air‐sea feedbacks over ocean eddies and fronts. The mesoscale thermal feedback (TFB) and the current feedback (CFB) are shown to influence the intensity of northern ECLs (north of ), with the TFB modulating the pre‐storm sea surface temperature (SST) by shifting ECL locations eastwards and the CFB modulating the wind stress. By fully uncoupling the atmospheric model of NOW, the intensity of northern ECLs is increased due to the absence of the cold wake that provides a negative feedback to the cyclone. The number of ECLs might also be affected by the air‐sea feedbacks but large interannual variability h ers significant results with short‐term simulations. The TFB and CFB modify the climatology of SST (mean and variability) but no direct link is found between these changes and those noticed in ECL properties. These results show that the representation of ECLs, mainly north of , depend on how air‐sea feedbacks are simulated. This is particularly important for atmospheric downscaling of climate projections as small‐scale SST interactions and the effects of ocean currents are not accounted for.
Categorizing and Naming Marine Heatwaves
Publisher: The Oceanography Society
Date: 06-2018
What Determines the Lagged ENSO Response in the South‐West Indian Ocean?
Publisher: American Geophysical Union (AGU)
Date: 24-03-2021
DOI: 10.1029/2020GL091958
Abstract: Oceanic Rossby waves can propagate climate signals over considerable distances over long timescales. Using a long simulation from a coupled climate model, we examine oceanic and mixed atmosphere‐ocean teleconnections to the south‐western Indian Ocean (SWIO) associated with Rossby waves excited by the El Niño‐Southern Oscillation (ENSO). Reconstruction of propagating ENSO‐induced sea‐level anomalies from the simulation using an optimized linear wave model with dissipation highlights the prominent role of baroclinic, rather than barotropic, Rossby waves in modulating sea‐surface heights. Between 9.5° and 18.5°S, El Niño‐associated anomalous anticyclonic wind‐stress fields initiate downwelling Rossby waves, potentially influencing SWIO regional climate around 1–4 seasons after El Niño peak, while also destructively interfering with upwelling waves triggered on the eastern boundary by oceanic teleconnections. Further south, weaker ENSO winds, dissipation, non‐linear processes, and interference from higher‐mode Rossby waves limit ENSO influences in the SWIO. In the model, ENSO‐associated predictability is therefore constrained by the “atmospheric” rather than “oceanic” bridge.
Regional connectivity and spatial densities of drifting fish aggregating devices, simulated from fishing events in the Western and Central Pacific Ocean
Publisher: IOP Publishing
Date: 06-2019
Abstract: The increased use of drifting Fish Aggregating Devices (dFADs) by tuna purse seine fleets in recent years has supported considerable catches of these species. A greater understanding of the spatiotemporal dynamics of these objects as they drift with ocean currents is critical for understanding historical changes in fishing power, spatial management, and examining the effect of ambient dFAD density on catch and effort. Here, dFAD dynamics were estimated for all floating object sets made by purse seiners in the Western and Central Pacific Ocean during 2016 and 2017. The drift trajectories of these floating objects prior to the observed fishing events were estimated by seeding virtual Lagrangian particles within a state-of-the-art hydrodynamics model, and simulating their movements backwards in time. Resulting trajectory distributions are similar to observed dFAD trajectories from the same period. The approach provides spatial density estimates in areas where observed dFAD data are incomplete, particularly in the exclusive economic zone (EEZ) of Howland and Baker Islands, and certain high seas areas. We provide estimates of inter-EEZ connectivity of dFADs, which highlight the fact that dFADs set upon in small EEZs such as Nauru and Howland and Baker Islands are likely to have drifted from neighbouring EEZs less than one month prior to fishing. dFADs typically transited multiple EEZs, with a median of 4 and a maximum of 14, when assuming a drift-time of six months. Moreover, between 4 and 22% of dFAD sets made in the WCPO were estimated to have originated from the Eastern Pacific Ocean, depending on drift-time. We examine our results in the context of the improved management and assessment of dFAD fisheries, providing a methodology to estimated relative dFAD density over historical periods to support analyses of catch and effort. The sensitivity of these estimates to hydrodynamic models, including the proposed SKIM doppler radar altimetry method, is discussed.
The Impact of Indonesian Throughflow Constrictions on Eastern Pacific Upwelling and Water‐Mass Transformation
Publisher: American Geophysical Union (AGU)
Date: 05-2022
DOI: 10.1029/2022JC018509
Abstract: The Indonesian Throughflow (ITF) is a key link in the global ocean overturning circulation. Heat gained from upwelling and watermass transformation in the eastern equatorial Pacific Ocean (PO) is transported through the ITF into the Indian Ocean, ultimately connecting to high‐latitude regions of heat loss such as the North Atlantic. However, state‐of‐the‐art General Circulation Models (GCMs) often poorly simulate upwelling, particularly in the eastern Pacific boundary regions. Recent studies have hypothesized that these difficulties may be related to biases in downstream ITF volume and heat transport, whereby insufficient warm surface water from the western PO passes through the ITF, a complex region that is hard to accurately represent in models. Here, we test this hypothesis using a coarse‐resolution ocean model by artificially widening the ITF and allowing greater quantities of warm water to exit the western PO. This reduces the Indo‐Pacific sea‐surface height and pressure gradient biases. Using diagnostics in temperature coordinates, we trace the source of increased ITF warm‐water transport to enhanced watermass transformation of cold‐to‐warm waters in the eastern tropical PO. Additional cool water is brought to the surface in the Cold Tongue region, resulting in an enhancement of surface flux‐driven warming. However, we find only limited evidence for changes in upwelling at lower temperatures along the eastern PO margins, considerably less than hypothesized in a previous study. Our experiment provides useful insights to help understand simulated ITF mass and heat transport biases and their links with the tropical PO in GCMs.
Northward ITCZ shift drives reduced ENSO activity in the Mid-Pliocene Warm Period
Publisher: Research Square Platform LLC
Date: 22-06-2021
DOI: 10.21203/RS.3.RS-402220/V1
Abstract: The El Niño Southern Oscillation (ENSO) is the strongest pattern of year-to-year climate variability found in the equatorial Pacific Ocean with global impacts. However, it is not fully understood how ENSO responds to different warming scenarios. In the warmer climate (~2-3K) of the mid-Pliocene Warm Period (~3 Ma BP), models consistently suggest a weakening of ENSO variability, with a mean reduction of 25% (±16%). We show that a near unanimous weakening of ENSO across models cannot be fully explained simply by mean state changes in the equatorial Pacific Ocean. Instead, robust off-equatorial mean state changes in the mid-Pliocene are not favourable for ENSO activity. A northward displacement of the Pacific Inter-Tropical Convergence Zone (ITCZ) is found to be significantly linked to the ENSO weakening across models. This is accompanied by increased south-easterly trade winds in the western Pacific and an intensified South Pacific Subtropical High, which are consistent with suppressed activity of processes that initiate ENSO. Our results provide a constraint to past and future changes to ENSO associated with the climatological ITCZ position.
Evaluation of monsoon seasonality and the tropospheric biennial oscillation transitions in the CMIP models
Publisher: American Geophysical Union (AGU)
Date: 26-10-2012
DOI: 10.1029/2012GL053322
Role of Pacific trade winds in driving ocean temperatures during the recent slowdown and projections under a wind trend reversal
Publisher: Springer Science and Business Media LLC
Date: 16-10-2017
Three-dimensional characterization and tracking of an Agulhas Ring
Publisher: Elsevier BV
Date: 08-2012
Indian Ocean Dipole in CMIP5 and CMIP6: characteristics, biases, and links to ENSO
Publisher: Springer Science and Business Media LLC
Date: 13-07-2020
DOI: 10.1038/S41598-020-68268-9
Abstract: Accurately representing the Indian Ocean Dipole (IOD) is crucial for reliable climate predictions and future projections. However, El Niño-Southern Oscillation (ENSO) and IOD interact, making it necessary to evaluate ENSO and IOD simultaneously. Using the historical simulation from 32 fifth phase of Coupled Model Intercomparison Project (CMIP5) models and 34 CMIP6 models, here we find that there are some modest changes in the basic characteristics of the IOD and ENSO from CMIP5 to CMIP6. Firstly, there is a slight shift in the seasonality of IOD toward an earlier peak in September in CMIP6, from November in CMIP5. Secondly, inter-model spread in the frequency of ENSO and the IOD has reduced in CMIP6 relative to CMIP5. ENSO asymmetry is still underestimated in CMIP6, based on the skewness of the Niño3 index, while the IOD skewness has degraded from CMIP5. Finally, mean state SST biases impact on the strength of the IOD the Pacific cold tongue mean state is important in CMIP5, but in CMIP6 the Pacific warm pool mean state is more important.
Socioeconomic impacts of marine heatwaves: Global issues and opportunities
Publisher: American Association for the Advancement of Science (AAAS)
Date: 22-10-2021
Abstract: Extreme warming events in the world’s oceans are becoming more widespread and frequent 8 of the 10 most severe recorded events have taken place in the past decade. Smith et al . review how these marine heatwaves are severely altering ecosystem service provision, with widespread socioeconomic impacts. Heatwave effects, including range shifts and mass mortality of marine species and harmful algal blooms, have knock-on economic consequences that already run into billions of US dollars. As well as reviewing the impacts of these events, the authors discuss the mitigation and adaptation measures that are needed to alleviate the risks and damaging impacts. —AMS
When 1+1 can be >2: Uncertainties compound when simulating climate, fisheries and marine ecosystems
Publisher: Elsevier BV
Date: 03-2015
Evaluation of Interior Circulation in a High-Resolution Global Ocean Model. Part II: Southern Hemisphere Intermediate, Mode, and Thermocline Waters
Publisher: American Meteorological Society
Date: 11-2007
Abstract: A high-resolution, offline ocean general circulation model, incorporating a realistic parameterization of mixed layer convection, is used to diagnose pathways and time scales of Southern Hemisphere intermediate, mode, and lower thermocline water ventilation. The use of such an offline methodology represents the only feasible way of simulating the long time scales required to validate the internal pathways of a high-resolution ocean model. Simulated and observed chlorofluorocarbon-11 (CFC-11) are in reasonably good agreement, demonstrating the model’s skill in representing realistic ventilation. Regional passive dye and age tracer experiments aid in the identification of pathways originating from different Southern Hemisphere locations. Northern Hemisphere penetration of intermediate, mode, and thermocline waters is most extensive and rapid into the North Atlantic Ocean because these waters are involved in closing the Atlantic meridional overturning cell. However, less than 8% of this ventilation is derived from subduction within the South Atlantic in the simulation. Instead, this water enters the Atlantic just to the south of South Africa, having originally subducted primarily in the east Indian Ocean, but also in the west Indian Ocean and the west Pacific region where a pathway advects water westward to the south of Australia. This pathway also plays a large part, together with water overturned in the east Indian Ocean, in ventilating the northern reaches of the Indian basin. Northward propagation in the Pacific Ocean is limited to the low latitudes of the Northern Hemisphere and is almost exclusively accomplished by water subducted in the South Pacific. A small contribution is made from the other basins from water that spreads northward, fed by a circumpolar pathway associated with the Antarctic Circumpolar Current that forms a conduit for intermediate and mode water exchange between all three basins. Intermediate water is injected into and branches off this pathway in all basins, but most vigorously in the southeastern Pacific.
Can Polar Stratospheric Clouds Explain Arctic Amplification?
Publisher: American Meteorological Society
Date: 15-04-2023
Abstract: Climate models underestimate the magnitude of Arctic warming in past warm climates, like the early Cretaceous and Paleogene periods, implying that certain physical processes might be missing or poorly represented. Previous studies suggest that a large increase in wintertime Arctic polar stratospheric clouds (PSCs) might have promoted Arctic lification through additional greenhouse warming. High methane concentrations in warm climates might have increased stratospheric water vapor providing favorable conditions for PSCs. However, methane concentrations in past warm climates are extremely uncertain. Here, we revisit the PSC hypothesis by exploring PSC changes under very high methane levels, 4× preindustrial carbon dioxide, and strong polar- lified surface warming, using a whole-atmosphere model with fully interactive chemistry. We find that with polar- lified warming there is a large increase in Arctic outgoing longwave radiation (OLR) that reduces as the methane concentration is increased. PSCs increase monotonically with methane concentration. A large radiative cooling and an increase in water vapor in the stratosphere increases Arctic PSCs, which follow a power law with respect to relative humidity. Using a two-way partial radiative perturbation technique, we show that the OLR reduction due to PSCs is similar to the direct radiative forcing of methane for high methane levels. Thus, we find that PSCs could play an important role in Arctic warming in a warmer-than-present-day climate, but only if methane levels were higher than suggested by previous modeling studies for past warm climates.
Marine Heatwaves
Publisher: Annual Reviews
Date: 03-01-2021
DOI: 10.1146/ANNUREV-MARINE-032720-095144
Abstract: Ocean temperature variability is a fundamental component of the Earth's climate system, and extremes in this variability affect the health of marine ecosystems around the world. The study of marine heatwaves has emerged as a rapidly growing field of research, given notable extreme warm-water events that have occurred against a background trend of global ocean warming. This review summarizes the latest physical and statistical understanding of marine heatwaves based on how they are identified, defined, characterized, and monitored through remotely sensed and in situ data sets. We describe the physical mechanisms that cause marine heatwaves, along with their global distribution, variability, and trends. Finally, we discuss current issues in this developing research area, including considerations related to thechoice of climatological baseline periods in defining extremes and how to communicate findings in the context of societal needs.
Australian Monsoon Variability Driven by a Gill–Matsuno-Type Response to Central West Pacific Warming
Publisher: American Meteorological Society
Date: 15-09-2010
Abstract: The objective of this study is to investigate the mechanisms that cause the anomalous intensification of tropical Australian rainfall at the height of the monsoon during El Niño Modoki events. In such events, northwestern Australia tends to be wetter in January and February when the SST warming is displaced to the central west Pacific, the opposite response to that associated with a traditional El Niño. In addition, during the bounding months, that is, December and March, there is below-average rainfall induced by an anomalous Walker circulation. This behavior tends to narrow and intensify the annual rainfall cycle over northwestern Australia relative to the climatology, causing a delayed monsoonal onset and an earlier retreat over the region. Observational datasets and numerical experiments with a general circulation model are used to examine the atmospheric response to the central west Pacific SST warming. It is shown here that the increase of precipitation, particularly in February, is phased locked to the seasonal cycle when the intertropical convergence zone is displaced southward and the South Pacific convergence zone is strengthened. An interaction between the interannual SST variability associated with El Niño Modoki events and the evolution of the seasonal cycle intensifies deep convection in the central west Pacific, driving a Gill–Matsuno-type response to the diabatic heating. The westward-propagating disturbance associated with the Gill–Matsuno mechanism generates an anomalous cyclonic circulation over northwestern Australia, leading to convergence of moisture and increased precipitation. The Gill–Matsuno-type response overwhelms the subsidence of the anomalous Walker circulation associated with Modoki events over Australia during the peak of the monsoon.
Probability of committed warming exceeding 1.5 ∘C and 2.0 ∘C Paris targets
Publisher: IOP Publishing
Date: 26-05-2022
Abstract: The feasibility of achieving the Paris 1.5 ∘ C target continues to be a complex and hotly debated question. To help resolve this question we calculate probability distributions of the committed warming that would ensue if all anthropogenic emissions were stopped immediately, or at successive future times. We use a simple Earth system model together with a Bayesian approach that incorporates multiple lines of evidence and accounts for known model biases. This analysis reveals a wide range of possible outcomes, including no further warming, but also a 15% chance of overshooting the 1.5 ∘ C target, and 1%–2% chance for 2 ∘ C, even if all emissions had stopped in 2020. If emissions merely stabilize in 2020 and stop in 2040, these probabilities increase to 90% and 17%. The uncertainty arises mainly from that of present forcing by aerosols. Rather than there being a fixed date by which emissions must stop, the probability of reaching either target—which is already below 100%—gradually diminishes with delays in eliminating emissions, by 3%–4% per year for 1.5 ∘ C.
Projected late 21st century changes to the regional impacts of the El Niño-Southern Oscillation
Publisher: Springer Science and Business Media LLC
Date: 12-10-2019
Projected slow down of South Indian Ocean circulation
Publisher: Springer Science and Business Media LLC
Date: 27-11-2019
DOI: 10.1038/S41598-019-54092-3
Abstract: Using an ensemble of 28 climate models, we examine hindcasts and ‘business as usual’ future changes to large-scale South Indian Ocean dynamics. We compare model ensemble seasonal-to-annual volume transports to observations and explore drivers of past and future circulation variability and change. Off the west coast of Australia, models consistently project a weakening of the Leeuwin Current and Undercurrent due to reduced onshore flow and downwelling. The reduced onshore flow is related to changes in the alongshore pressure gradient. While the alongshore pressure gradient change is consistent with the Indonesian Throughflow projected weakening, we found no inter-model relationship between these changes. In the south-western Indian Ocean, the models project a robust weakening of the North East and South East Madagascar Currents, Agulhas Current and transport through the Mozambique Channel. This reduced Indian Ocean western boundary flow is partly associated with a weaker Indonesian Throughflow and overturning circulation, where the latter is related to a decrease in the convergence of deep Southern Ocean waters into the Indian Ocean. In contrast to the weakening of other features, the westward flowing Agulhas Current extension south of Africa is projected to strengthen, which is consistent with an intensification of the Antarctic Circumpolar Current.
The Contribution of Indian Ocean Sea Surface Temperature Anomalies on Australian Summer Rainfall during El Niño Events
Publisher: American Meteorological Society
Date: 15-07-2011
Abstract: This study investigates the impact of Indian Ocean sea surface temperature (SST) anomalies on the atmospheric circulation of the Southern Hemisphere during El Niño events, with a focus on Australian climate. During El Niño episodes, the tropical Indian Ocean exhibits two types of SST response: a uniform “basinwide warming” and a dipole mode—the Indian Ocean dipole (IOD). While the impacts of the IOD on climate have been extensively studied, the effects of the basinwide warming, particularly in the Southern Hemisphere, have received less attention. The interannual basinwide warming response has important implications for Southern Hemisphere atmospheric circulation because 1) it accounts for a greater portion of the Indian Ocean monthly SST variance than the IOD pattern and 2) its maximum litude occurs during austral summer to early autumn, when large parts of Australia, South America, and Africa experience their monsoon. Using observations and numerical experiments with an atmospheric general circulation model forced with historical SST from 1949 to 2005 over different tropical domains, the authors show that the basinwide warming leads to a Gill–Matsuno-type response that reinforces the anomalies caused by changes in the Pacific as part of El Niño. In particular, the basinwide warming drives strong subsidence over Australia, prolonging the dry conditions during January–March, when El Niño–related SST starts to decay. In addition to the anomalous circulation in the tropics, the basinwide warming excites a pair of barotropic anomalies in the Indian Ocean extratropics that induces an anomalous anticyclone in the Great Australian Bight.
Corrigendum to “Multi-decadal projections of surface and interior pathways of the Fukushima cesium-137 radioactive plume” [Deep-Sea Res. I 80 (2013) 37–46]
Publisher: Elsevier BV
Date: 11-2014
Coordinated Ocean-ice Reference Experiments (COREs)
Publisher: Elsevier BV
Date: 2009
CORRIGENDUM
Publisher: American Meteorological Society
Date: 12-2013
Multi-decadal modulation of the El Niño–Indian monsoon relationship by Indian Ocean variability
Publisher: IOP Publishing
Date: 07-2011
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