ORCID Profile
0000-0001-5156-2204
Current Organisations
University of Sydney
,
University of Tasmania
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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 | Oceanography | Climate Change Processes | Physical oceanography | Meteorology | Climate change processes | Atmospheric dynamics | Atmospheric Sciences | Atmospheric sciences | Glaciology | Atmospheric Sciences not elsewhere classified | Climatology (excl. Climate Change Processes) | Numerical Computation
ANZSRC Socio-Economic Objective (SEO)
Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Climate Change Models | Physical and Chemical Conditions of Water in Marine Environments | Expanding Knowledge in the Environmental Sciences | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Expanding Knowledge in the Earth Sciences | Expanding Knowledge in the Information and Computing Sciences |
Related Links
Publications
Natural carbon release compensates for anthropogenic carbon uptake when Southern Hemispheric westerlies strengthen
Publisher: Wiley
Date: 02-10-2021
Vigorous deep-sea currents cause global anomaly in sediment accumulation in the Southern Ocean
Publisher: Geological Society of America
Date: 08-07-2016
DOI: 10.1130/G38143.1
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.
Subtropical-tropical pathways of spiciness anomalies and their impact on equatorial Pacific temperature
Publisher: Springer Science and Business Media LLC
Date: 27-11-2021
Climate simulations of the Permian-Triassic boundary: Ocean acidification and the extinction event
Publisher: American Geophysical Union (AGU)
Date: 02-08-2011
DOI: 10.1029/2010PA002058
Separating the influence of projected changes in air temperature and wind on patterns of sea level change and ocean heat content
Publisher: American Geophysical Union (AGU)
Date: 08-2015
DOI: 10.1002/2015JC010928
Warm Circumpolar Deep Water transport toward Antarctica driven by local dense water export in canyons
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-2020
Abstract: Mid-depth heat transport toward Antarctica is focused in “cold” regions, mechanically forced by overflowing dense water.
Direct and Indirect Pathways of Convected Water Masses and Their impacts on the Overturning Dynamics of the Labrador Sea
Publisher: American Geophysical Union (AGU)
Date: 2021
DOI: 10.1029/2020JC016654
North Atlantic Climate Response to Lake Agassiz Drainage at Coarse and Ocean Eddy-Permitting Resolutions
Publisher: American Meteorological Society
Date: 15-04-2013
DOI: 10.1175/JCLI-D-11-00683.1
Abstract: The North Atlantic climate response to the catastrophic drainage of proglacial Lake Agassiz into the Labrador Sea is analyzed with coarse and ocean eddy-permitting versions of a global coupled climate model. The North Atlantic climate response is qualitatively consistent in that a large-scale cooling is simulated regardless of the model resolution or region of freshwater discharge. However, the magnitude and duration of the North Atlantic climate response is found to be sensitive to model resolution and the location of freshwater forcing. In particular, the long-term entrainment of freshwater along the boundary at higher resolution and its gradual, partially eddy-driven escape into the interior leads to low-salinity anomalies persisting in the subpolar Atlantic for decades longer. As a result, the maximum decline of the Atlantic meridional overturning circulation (AMOC) and the ocean meridional heat transport (MHT) is lified by about a factor of 2 at ocean eddy-permitting resolution, and the recovery is delayed relative to the coarse grid model. This, in turn, increases the long-term cooling in the high-resolution simulations. A decomposition of the MHT response reveals an increased role for transients and the horizontal mean component of MHT at higher resolution. With fixed wind stress curl, it is a stronger response of bottom pressure torque to the freshwater forcing at higher resolution that leads to a larger anomaly of the depth-integrated circulation.
Ice-Shelf Melt Response to Changing Winds and Glacier Dynamics in the Amundsen Sea Sector, Antarctica
Publisher: American Geophysical Union (AGU)
Date: 12-2017
DOI: 10.1002/2017JC013059
Surface Ocean Warming Around Australia Driven by Interannual Variability and Long‐Term Trends in Southern Hemisphere Westerlies
Publisher: American Geophysical Union (AGU)
Date: 29-04-2020
DOI: 10.1029/2019GL086605
The Key Role of the Western Boundary in Linking the AMOC Strength to the North–South Pressure Gradient
Publisher: American Meteorological Society
Date: 04-2012
Abstract: A key idea in the study of the Atlantic meridional overturning circulation (AMOC) is that its strength is proportional to the meridional density gradient or, more precisely, to the strength of the meridional pressure gradient. A physical basis that would indicate how to estimate the relevant meridional pressure gradient locally from the density distribution in numerical ocean models to test such an idea has been lacking however. Recently, studies of ocean energetics have suggested that the AMOC is driven by the release of available potential energy (APE) into kinetic energy (KE) and that such a conversion takes place primarily in the deep western boundary currents. In this paper, the authors develop an analytical description linking the western boundary current circulation below the interface separating the North Atlantic Deep Water (NADW) and Antarctic Intermediate Water (AAIW) to the shape of this interface. The simple analytical model also shows how available potential energy is converted into kinetic energy at each location and that the strength of the transport within the western boundary current is proportional to the local meridional pressure gradient at low latitudes. The present results suggest, therefore, that the conversion rate of potential energy may provide the necessary physical basis for linking the strength of the AMOC to the meridional pressure gradient and that this could be achieved by a detailed study of the APE to KE conversion in the western boundary current.
Sea level changes forced by Southern Ocean winds
Publisher: American Geophysical Union (AGU)
Date: 05-11-2013
DOI: 10.1002/2013GL058104
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
Testing the sensitivity of the East Antarctic Ice Sheet to Southern Ocean dynamics: past changes and future implications
Publisher: Wiley
Date: 26-12-2014
DOI: 10.1002/JQS.2683
ENSO-driven interhemispheric Pacific mass transports
Publisher: American Geophysical Union (AGU)
Date: 09-2014
DOI: 10.1002/2014JC010286
Barotropic Kelvin Wave‐Induced Bottom Boundary Layer Warming Along the West Antarctic Peninsula
Publisher: American Geophysical Union (AGU)
Date: 03-2019
DOI: 10.1029/2018JC014227
The effect on simulated ocean climate of a parameterization of unbroken wave‐induced mixing incorporated into the k‐epsilon mixing scheme
Publisher: American Geophysical Union (AGU)
Date: 04-2017
DOI: 10.1002/2016MS000707
Mechanisms Maintaining Southern Ocean Meridional Heat Transport under Projected Wind Forcing
Publisher: American Meteorological Society
Date: 11-2012
Abstract: Meridional heat transport (MHT) in the Southern Ocean (SO) and its components are analyzed with two eddy-permitting climate models. The two models present a consistent picture of the MHT response to projected twenty-first-century changes in SO winds. In agreement with a recent analysis based on an ocean data synthesis product, much of the MHT in the SO is found to be due to the time-mean fields of meridional velocity and temperature. The change in the net MHT tends to be small relative to the interannual variability at most SO latitudes. However, both models exhibit significant changes at most latitudes south of 30°S in in idual components of MHT. A simple framework wherein changes in the eddy and mean heat transports tend to compensate each other is not supported by the authors’ results. Instead, the MHT response is composed of sizeable contributions from essentially all of the MHT components, with the eddy and mean heat transports often having the same sign.
Southern Australia Current System based on a gridded hydrography and a high-resolution model
Publisher: Elsevier BV
Date: 02-2020
An assessment of the Arctic Ocean in a suite of interannual CORE-II simulations. Part III: Hydrography and fluxes
Publisher: Elsevier BV
Date: 04-2016
Rapid subsurface warming and circulation changes of Antarctic coastal waters by poleward shifting winds
Publisher: American Geophysical Union (AGU)
Date: 12-07-2014
DOI: 10.1002/2014GL060613
The Atlantic meridional overturning circulation in high resolution models
Publisher: American Geophysical Union (AGU)
Date: 04-2020
DOI: 10.1029/2019JC015522
Natural carbon release compensates for anthropogenic carbon uptake when Southern Hemispheric westerlies strengthen
Publisher: Wiley
Date: 31-08-2020
The role of vertical eddy flux in Southern Ocean heat uptake
Publisher: American Geophysical Union (AGU)
Date: 17-10-2013
DOI: 10.1002/2013GL057706
The Sensitivity of the Atlantic Meridional Overturning Circulation to Freshwater Forcing at Eddy-Permitting Resolutions
Publisher: American Meteorological Society
Date: 06-2008
Abstract: The effect of increasing horizontal resolution is examined to assess the response of the Atlantic meridional overturning circulation (AMOC) to freshwater perturbations. Versions of a global climate model with horizontal resolutions ranging from 1.8° (latitude) × 3.6° (longitude) to 0.2° × 0.4° are used to determine if the AMOC response to freshwater forcing is robust to increasing resolution. In the preindustrial equilibrium climate, the representation of western boundary currents and meridional heat transport are improved with resolution. Freshwater forcings similar to the final drainage of proglacial Lakes Agassiz and Ojibway are applied evenly over the Labrador Sea and exclusively along the western boundary. The duration and maximum litude of model responses to freshwater forcing showed little sensitivity to increasing resolution. An evaluation with tracers of the forcing impact on different regions of North Atlantic Deep Water formation revealed the possibility that increases in Labrador Sea deep convection at higher resolution mitigate the effect of stronger boundary currents and enhanced mixing. With increasing resolution, there is less cooling in the subpolar west Atlantic, more cooling in the subpolar east Atlantic, and greater variability in the deep ocean response to the boundary forcing. While differences exist, the coarse-resolution model response remains robust at finer horizontal resolutions.
Meridional movement of wind anomalies during ENSO events and their role in event termination
Publisher: American Geophysical Union (AGU)
Date: 21-02-2013
DOI: 10.1002/GRL.50136
Sea Level and the Role of Coastal Trapped Waves in Mediating the Influence of the Open Ocean on the Coast
Publisher: Springer Science and Business Media LLC
Date: 02-05-2019
Southern Hemisphere westerlies as a driver of the early deglacial atmospheric CO2 rise
Publisher: Springer Science and Business Media LLC
Date: 27-06-2018
DOI: 10.1038/S41467-018-04876-4
Abstract: The early part of the last deglaciation is characterised by a ~40 ppm atmospheric CO 2 rise occurring in two abrupt phases. The underlying mechanisms driving these increases remain a subject of intense debate. Here, we successfully reproduce changes in CO 2 , δ 13 C and Δ 14 C as recorded by paleo-records during Heinrich stadial 1 (HS1). We show that HS1 CO 2 increase can be explained by enhanced Southern Ocean upwelling of carbon-rich Pacific deep and intermediate waters, resulting from intensified Southern Ocean convection and Southern Hemisphere (SH) westerlies. While enhanced Antarctic Bottom Water formation leads to a millennial CO 2 outgassing, intensified SH westerlies induce a multi-decadal atmospheric CO 2 rise. A strengthening of SH westerlies in a global eddy-permitting ocean model further supports a multi-decadal CO 2 outgassing from the Southern Ocean. Our results highlight the crucial role of SH westerlies in the global climate and carbon cycle system with important implications for future climate projections.
Vertical resolution of baroclinic modes in global ocean models
Publisher: Elsevier BV
Date: 05-2017
Response of Southern Ocean Ventilation to Changes in Midlatitude Westerly Winds
Publisher: American Meteorological Society
Date: 09-2019
Abstract: Changes in ventilation of the Southern Hemisphere oceans in response to changes in midlatitude westerly winds are examined by analyzing the ideal age tracer from global eddy-permitting ocean–ice model simulations in which there is an abrupt increase and/or a meridional shift in the winds. The age response in mode and intermediate waters is found to be close to linear the response of a combined increase and shift of peak winds is similar to the sum of the in idual responses to an increase and a shift. Further, a barotropic response, following Sverdrup balance, can explain much of the age response to the changes in wind stress. There are similar peak decreases (of around 50 years) in the ideal age for a 40% increase or 2.5° poleward shift in the wind stress. However, while the age decreases throughout the thermocline for an increase in the winds, for a poleward shift in the winds the age increases in the north part of the thermocline and there are decreases in age only south of 35°S. As a consequence, the change in the volume of young water differs, with a 15% increase in the volume of water with ages younger than 50 years for a 40% increase in the winds but essentially no change in this volume for a 2.5° shift. As ventilation plays a critical role in the uptake of carbon and heat, these results suggest that the storage of anthropogenic carbon and heat in mode and intermediate waters will likely increase with a strengthening of the winds, but will be much less sensitive to a meridional shift in the peak wind stress.
Pathways and watermass transformation of Atlantic Water entering the Nordic Seas through Denmark Strait in two high resolution ocean models
Publisher: Elsevier BV
Date: 03-2019
The Antarctic Slope Current in a Changing Climate
Publisher: American Geophysical Union (AGU)
Date: 12-2018
DOI: 10.1029/2018RG000624
Contribution of enhanced Antarctic Bottom Water formation to Antarctic warm events and millennial-scale atmospheric CO2 increase
Publisher: Elsevier BV
Date: 03-2015
Propagation of barotropic Kelvin waves around Antarctica
Publisher: Springer Science and Business Media LLC
Date: 05-05-2022
DOI: 10.1007/S10236-022-01506-Y
Abstract: Barotropic (i.e., depth-uniform) coastal oceanic Kelvin waves can provide rapid teleconnections from climate and weather events in one location to remote regions of the globe. Studies suggest that barotropic Kelvin waves observed around Antarctica may provide a mechanism for rapidly propagating circulation anomalies around the continent, with implications for continental shelf temperatures along the West Antarctic Peninsula and thus Antarctic ice mass loss rates. However, how the propagation of Kelvin waves around Antarctica is influenced by features such as coastal geometry and variations in bathymetry remains poorly understood. Here we study the propagation of barotropic Antarctic Kelvin waves using a range of idealized model simulations. Using a single-layer linear shallow water model with 1 ∘ horizontal resolution, we gradually add complexity of continental configuration, realistic bathymetry, variable planetary rotation, and forcing scenarios, to isolate sources and sinks of wave energy and the mechanisms responsible. We find that approximately 75 % of sub-inertial barotropic Kelvin wave energy is scattered away from Antarctica as other waves in one circumnavigation of the continent, due mostly to interactions with bathymetry. Super-inertial barotropic Kelvin waves lose nearly 95 % of their energy in one circumpolar loop, due to interactions with both coastal geometry and bathymetry. These results help to explain why only sustained signals of low-frequency resonant barotropic Kelvin waves have been observed around Antarctica, and contribute to our understanding of the role of rapid, oceanic teleconnections in climate.
Mixed layer depth calculation in deep convection regions in ocean numerical models
Publisher: Elsevier BV
Date: 12-2017
Understanding variability of the Southern Ocean overturning circulation in CORE-II models
Publisher: Elsevier BV
Date: 03-2018
The Energetics of Southern Ocean Upwelling
Publisher: American Meteorological Society
Date: 2017
Abstract: The ocean’s meridional overturning circulation is closed by the upwelling of dense, carbon-rich waters to the surface of the Southern Ocean. It has been proposed that upwelling in this region is driven by strong westerly winds, implying that the intensification of Southern Ocean winds in recent decades may have enhanced the rate of upwelling, potentially affecting the global overturning circulation. However, there is no consensus on the sensitivity of upwelling to winds or on the nature of the connection between Southern Ocean processes and the global overturning circulation. In this study, the sensitivity of the overturning circulation to changes in Southern Ocean westerly wind stress is investigated using an eddy-permitting ocean–sea ice model. In addition to a suite of standard circulation metrics, an energy analysis is used to aid dynamical interpretation of the model response. Increased Southern Ocean wind stress enhances the upper cell of the overturning circulation through creation of available potential energy in the Southern Hemisphere, associated with stronger upwelling of deep water. Poleward shifts in the Southern Ocean westerlies lead to a complicated transient response, with the formation of bottom water induced by increased polynya activity in the Weddell Sea and a weakening of the upper overturning cell in the Northern Hemisphere. The energetic consequences of the upper overturning cell response indicate an interhemispheric connection to the input of available potential energy in the Northern Hemisphere.
The Role of Bottom Pressure Torques on the Interior Pathways of North Atlantic Deep Water
Publisher: American Meteorological Society
Date: 2012
Abstract: Four versions of the same global climate model, one with horizontal resolution of 1.8° × 3.6° and three with 0.2° × 0.4°, are employed to evaluate the role of ocean bottom topography and viscosity on the spatial structure of the deep circulation. This study is motivated by several recent observational studies that find that subsurface floats injected near the western boundary of the Labrador Sea most often do not continuously follow the deep western boundary current (DWBC), in contrast to the traditional view that the deep water formed in the North Atlantic predominantly follows the DWBC. It is found that, with imposed large viscosity values, the model reproduces the traditional view. However, as viscosity is reduced and the model bathymetry resolution increased, much of the North Atlantic Deep Water (NADW) separates from the western boundary and enters the low-latitude Atlantic via interior pathways distinct from the DWBC. It is shown that bottom pressure torques play an important role in maintaining these interior NADW outflows.
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
The separation of the E ast A ustralian C urrent: A L agrangian approach to potential vorticity and upstream control
Publisher: American Geophysical Union (AGU)
Date: 2016
DOI: 10.1002/2015JC011133
Hemispheric Asymmetry of the Pacific Shallow Meridional Overturning Circulation
Publisher: American Geophysical Union (AGU)
Date: 08-2019
DOI: 10.1029/2018JC014840
Ocean circulation and sea-ice thinning induced by melting ice shelves in the Amundsen Sea
Publisher: American Geophysical Union (AGU)
Date: 03-2017
DOI: 10.1002/2016JC012509
Anisotropy of eddy variability in the global ocean
Publisher: Elsevier BV
Date: 11-2015
Localized rapid warming of West Antarctic subsurface waters by remote winds
Publisher: Springer Science and Business Media LLC
Date: 17-07-2017
DOI: 10.1038/NCLIMATE3335
ACCESS-OM2: A Global Ocean-Sea Ice Model at Three Resolutions
Publisher: Copernicus GmbH
Date: 30-04-2019
DOI: 10.5194/GMD-2019-106
Abstract: Abstract. We introduce a new version of the ocean-sea ice implementation of the Australian Community Climate and Earth System Simulator, ACCESS-OM2. The model has been developed with the aim of being aligned as closely as possible with the fully coupled (atmosphere-land-ocean-sea ice) ACCESS-CM2. Importantly, the model is available at three different horizontal resolutions: a coarse resolution (nominally 1° horizontal grid spacing), an eddy-permitting resolution (nominally 0.25°) and an eddy-rich resolution (0.1° with 75 vertical levels), where the eddy-rich model is designed to be incorporated into the Bluelink operational ocean prediction and reanalysis system. The different resolutions have been developed simultaneously, both to allow testing at lower resolutions and to permit comparison across resolutions. In this manuscript, the model is introduced and the in idual components are documented. The model performance is evaluated across the three different resolutions, highlighting the relative advantages and disadvantages of running ocean-sea ice models at higher resolution. We find that higher resolution is an advantage in resolving flow through small straits, the structure of western boundary currents and the abyssal overturning cell, but that there is scope for improvements in sub-grid scale parameterisations at the highest resolution.
Controls on the global distribution of contourite drifts: Insights from an eddy-resolving ocean model
Publisher: Elsevier BV
Date: 05-2018
Planetary-wave induced strengthening of the AMOC forced by poleward intensified Southern Hemisphere westerly winds
Publisher: American Meteorological Society
Date: 11-05-2021
Abstract: The Atlantic meridional overturning circulation (AMOC) plays a key role in determining the distribution of heat and nutrients in the global ocean. Climate models suggest that Southern Ocean winds will strengthen and shift poleward in the future, which could have implications for future AMOC trends. Using a coupled global-ocean sea-ice model at 1/4°horizontal resolution, we study the response of the North Atlantic overturning to two anomalous Southern Ocean wind-forcing ( τ +15% ), and a poleward intensification( ). In both scenarios a strengthening in the North Atlantic overturning develops within a decade, with a much stronger response in the case. In , we find that the primary link between the North Atlantic response and the Southern Ocean forcing is via the propagation of baroclinic waves. In fact, due to the rapid northward propagation of these waves, changes in the AMOC in the case appear to originate in the North Atlantic and propagate southward, whereas in the τ +15% case AMOC anomalies propagate northward from the Southern Ocean. We find the difference to be predominately caused by the sign of the baroclinic waves propagating from the forcing region into the North Atlantic downwelling in the τ +15% case, versus upwelling in the case. In the case, upwelling waves propagating into the NADW formation regions along shelf-slope topography bringing dense water to the surface. This reduces vertical density gradients leading to deeper wintertime convective overturn of surface waters, and an intensification of the AMOC.
Enhanced Mid‐depth Southward Transport in the Northeast Atlantic at the Last Glacial Maximum Despite a Weaker AMOC
Publisher: American Geophysical Union (AGU)
Date: 02-2020
DOI: 10.1029/2019PA003793
The Impact of Tropical Atlantic Freshwater Fluxes on the North Atlantic Meridional Overturning Circulation
Publisher: American Meteorological Society
Date: 15-09-2006
DOI: 10.1175/JCLI3873.1
Abstract: The influence of ENSO-related changes in the Atlantic-to-Pacific freshwater budget on the North Atlantic meridional overturning is examined using the University of Victoria (UVic) Earth System Climate Model. The initial analysis of freshwater fluxes in the 50-yr NCEP–NCAR (NCEP50) reanalysis product and Global Precipitation Climatology Project (GPCP) dataset reveals that the transport of water vapor out of the tropical Atlantic drainage basin is enhanced during El Niño phases and reduced during La Niña phases a one standard deviation in the Southern Oscillation index alters the tropical Atlantic freshwater balance by about 0.09 Sv (Sv ≡ 106 m3 s−1). A weaker link with ENSO is found in the 40-yr ECMWF Re-Analysis (ERA-40), although its usefulness is severely limited by a strong and spurious trend in tropical precipitation. Model results suggest that tropical Atlantic salinity anomalies generated with the frequency and litude of ENSO tend not to impact deep-water formation as they are diluted en route to the North Atlantic. Lower frequency, decadal time-scale anomalies, however, do have an impact, albeit weak, on the rate of North Atlantic Deep Water formation. In addition, and contrary to earlier results, it is found that even a shift of the tropical Atlantic freshwater balance toward permanent El Niño conditions only slightly mitigates the transient reduction of North Atlantic Deep Water formation associated with the increase of anthropogenic greenhouse gases. Taken together, the results suggest that the poleward propagation of salinity anomalies from the tropical Atlantic, associated with changes in ENSO, should not be considered a significant mechanism for the variability of the North Atlantic meridional overturning in the present and foreseeable future climate.
Abyssal connections of Antarctic Bottom Water in a Southern Ocean State Estimate
Publisher: American Geophysical Union (AGU)
Date: 28-05-2013
DOI: 10.1002/GRL.50483
An assessment of the Arctic Ocean in a suite of interannual CORE-II simulations. Part I: Sea ice and solid freshwater
Publisher: Elsevier BV
Date: 03-2016
An assessment of the Arctic Ocean in a suite of interannual CORE-II simulations. Part II: Liquid freshwater
Publisher: Elsevier BV
Date: 03-2016
Using Eulerian and Lagrangian Approaches to Investigate Wind-Driven Changes in the Southern Ocean Abyssal Circulation
Publisher: American Meteorological Society
Date: 02-2014
Abstract: This study uses a global ocean eddy-permitting climate model to explore the export of abyssal water from the Southern Ocean and its sensitivity to projected twenty-first-century poleward-intensifying Southern Ocean wind stress. The abyssal flow pathways and transport are investigated using a combination of Lagrangian and Eulerian techniques. In an Eulerian format, the equator- and poleward flows within similar abyssal density classes are increased by the wind stress changes, making it difficult to explicitly diagnose changes in the abyssal export in a meridional overturning circulation framework. Lagrangian particle analyses are used to identify the major export pathways of Southern Ocean abyssal waters and reveal an increase in the number of particles exported to the subtropics from source regions around Antarctica in response to the wind forcing. Both the Lagrangian particle and Eulerian analyses identify transients as playing a key role in the abyssal export of water from the Southern Ocean. Wind-driven modifications to the potential energy component of the vorticity balance in the abyss are also found to impact the Southern Ocean barotropic circulation.
Southern Ocean Response to Strengthening Winds in an Eddy-Permitting Global Climate Model
Publisher: American Meteorological Society
Date: 10-2010
Abstract: A global climate model with horizontal resolutions in the ocean ranging from relatively coarse to eddy permitting is used to investigate the resolution dependence of the Southern Ocean response to poleward intensifying winds through the past and present centuries. The higher-resolution simulations show poleward migration of distinct ocean fronts associated with a more highly localized near-surface temperature response than in the lower-resolution simulations. The higher-resolution simulations also show increasing southward eddy heat transport, less high-latitude cooling, and greater sea ice loss than the lower-resolution simulations. For all resolutions, from relatively coarse to eddy permitting, there is poleward migration of the Antarctic Circumpolar Current in the Atlantic and the western half of the Indian basin. Finally, zonal transports associated with the Antarctic Circumpolar Current are shown to be sensitive to resolution, and this is discussed in the context of recent observed change.
Changes in Ocean Heat Content Caused by Wave-Induced Mixing in a High-Resolution Ocean Model
Publisher: American Meteorological Society
Date: 05-2018
Abstract: A parameterization of turbulent mixing from unbroken surface waves is included in a 16-yr simulation within a high-resolution ocean circulation model (MOM5). This “surface wave mixing” (SWM) derives from the wave orbital motion and is parameterized as an additional term in a k -epsilon model. We show that SWM leads to significant changes in sea surface temperatures but smaller changes in ocean heat content, and show the extent to which these changes can reduce pre-existing model biases with respect to observed data. Specifically, SWM leads to a widespread improvement in sea surface temperature in both hemispheres in summer and winter, while for ocean heat content the improvements are less clear. In addition, we show that introducing SWM can lead to an accumulation of wave-induced ocean heat content between years. While it has been well established that secular positive trends exist in global wave heights, we find that such trends are relatively unimportant in driving the accumulation of wave-induced ocean heat content. Rather, in response to the new source of mixing, the simulated ocean climate evolves toward a new equilibrium with greater total ocean heat content.
The Southern Ocean Overturning: Parameterized versus Permitted Eddies
Publisher: American Meteorological Society
Date: 07-2009
Abstract: Four versions of the same global climate model, with horizontal resolution ranging from 1.8° × 3.6° to 0.2° × 0.4°, are employed to evaluate the resolution dependence of the Southern Ocean meridional overturning circulation. At coarse resolutions North Atlantic Deep Water tends to upwell diabatically at low latitudes, so that the Southern Ocean is weakly coupled with the rest of the ocean. As resolution increases and eddy effects become less parameterized the interior circulation becomes more adiabatic and deep water increasingly upwells by flowing along isopycnals in the Southern Ocean, despite each model having the same vertical diffusivity profile. Separating the overturning circulation into mean and eddy-induced components demonstrates that both the permitted and the parameterized eddies induce overturning cells in the Southern Ocean with mass fluxes across mean isopycnals. It is found that for some density classes the transformation rate derived from surface buoyancy fluxes can provide a proxy for the net meridional transport in the upper Southern Ocean. Changes in the Southern Ocean overturning in response to poleward-intensifying Southern Hemisphere winds concomitant with increasing atmospheric CO2 through the twenty-first century are also investigated. Results suggest that the circulation associated with the formation of Antarctic Intermediate Water is likely to strengthen, or stay essentially unchanged, rather than to slow down.
Regional Impacts of the Westerly Winds on Southern Ocean Mode and Intermediate Water Subduction
Publisher: American Meteorological Society
Date: 10-2017
Abstract: Subduction processes in the Southern Ocean transfer oxygen, heat, and anthropogenic carbon into the ocean interior. The future response of upper-ocean subduction, in the Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) classes, is dependent on the evolution of the combined surface buoyancy forcing and overlying westerly wind stress. Here, the recently observed pattern of a poleward intensification of the westerly winds is ided into its shift and increase components. SAMW and AAIW formation occurs in regional “hot spots” in deep mixed layer zones, primarily in the southeast Indian and Pacific. It is found that the mixed layer depth responds differently to wind stress perturbations across these regional formation zones. An increase only in the westerly winds in the Indian sector steepens isopycnals and increases the local circulation, driving deeper mixed layers and increased subduction. Conversely, in the same region, a poleward shift and poleward intensification of the westerly winds reduces heat loss and increases freshwater input, thus decreasing the mixed layer depth and consequently the associated SAMW and AAIW subduction. In the Pacific sector, all wind stress perturbations lead to increases in heat loss and decreases in freshwater input, resulting in a net increase in SAMW and AAIW subduction. Overall, the poleward shift in the westerly wind stress dominates the SAMW subduction changes, rather than the increase in wind stress. The net decrease in SAMW subduction across all basins would likely decrease anthropogenic carbon sequestration however, the net AAIW subduction changes across the Southern Ocean are overall minor.
Poleward Shift in the Southern Hemisphere Westerly Winds Synchronous With the Deglacial Rise in CO2
Publisher: American Geophysical Union (AGU)
Date: 28-06-2023
DOI: 10.1029/2023PA004666
Abstract: The Southern Hemisphere westerly winds influence deep ocean circulation and carbon storage. While the westerlies are hypothesized to play a key role in regulating atmospheric CO 2 over glacial‐interglacial cycles, past changes in their position and strength remain poorly constrained. Here, we use a compilation of planktic foraminiferal δ 18 O from across the Southern Ocean and emergent relationships within an ensemble of climate models to reconstruct changes in the Southern Hemisphere surface westerlies over the last deglaciation. We infer a 4.8° (2.9–7.1°, 95% confidence interval) equatorward shift and about a 25% weakening of the westerlies during the Last Glacial Maximum (20 ka) relative to the mid‐Holocene (6.5 ka). Climate models from the Palaeoclimate Modeling Intercomparison Project substantially underestimate this inferred equatorward wind shift. According to our reconstruction, the poleward shift in the westerlies over deglaciation closely mirrors the rise in atmospheric CO 2 ( R 2 = 0.98). Experiments with a 0.25° resolution ocean‐sea‐ice‐carbon model suggest that shifting the westerlies equatorward reduces the overturning rate of the ocean below 2 km depth, leading to a suppression of CO 2 outgassing from the polar Southern Ocean. Our results support a role for the westerly winds in driving the deglacial CO 2 rise, and suggest outgassing of natural CO 2 from the Southern Ocean is likely to increase as the westerlies shift poleward due to anthropogenic warming.
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