ORCID Profile
0000-0002-7055-9876
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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)
Oceanography | Physical Oceanography | Physical Oceanography | Biological Oceanography | Climatology (Incl. Palaeoclimatology) | Genetics | Chemical Oceanography | Climate Change Processes | Gene Expression | Genome Structure | Marine And Estuarine Ecology (Incl. Marine Ichthyology) | Microbial Ecology
ANZSRC Socio-Economic Objective (SEO)
Climate variability | Oceanic processes (excl. climate related) | Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Antarctic and Sub-Antarctic Oceanography | Marine Oceanic Processes (excl. climate related) | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Living resources (flora and fauna) | Climate Variability (excl. Social Impacts) | Climate change | Living resources (incl. impacts of fishing on non-target species) | Physical and Chemical Conditions of Water in Marine Environments | Integrated (ecosystem) assessment and management | Other |
Related Links
Publications
Vulnerability of Denman Glacier to Ocean Heat Flux Revealed by Profiling Float Observations
Publisher: American Geophysical Union (AGU)
Date: 22-09-2022
DOI: 10.1029/2022GL100460
Abstract: Denman Glacier, which drains a marine‐based sector of the East Antarctic Ice Sheet with an ice volume equivalent to 1.5 m of global sea level rise, has accelerated and undergone grounding line retreat in recent decades. A deep trough and retrograde bed slope inward of the grounding line leave this glacier prone to marine ice sheet instability. The ocean heat flux to the ice shelf cavity is a critical factor determining the susceptibility of the glacier to unstable retreat. Profiling float observations show modified Circumpolar Deep Water as warm as −0.16°C reaches a deep trough extending beneath the Denman Ice Tongue. The ocean heat transport (0.77 ± 0.35 TW) is sufficient to drive high rates of basal melt (70.8 ± 31.5 Gt y −1 ), consistent with rates inferred from glaciological observations. These results suggest the Denman Glacier is potentially at risk of unstable retreat triggered by transport of warm water to the ice shelf cavity.
A 6 year record of baroclinic transport variability of the Antarctic Circumpolar Current at 140°E derived from expendable bathythermograph and altimeter measurements
Publisher: American Geophysical Union (AGU)
Date: 10-2002
DOI: 10.1029/2001JC000787
Circulation of modified Circumpolar Deep Water and basal melt beneath the Amery Ice Shelf, East Antarctica
Publisher: American Geophysical Union (AGU)
Date: 04-2015
DOI: 10.1002/2015JC010697
Abstract: Antarctic ice sheet mass loss has been linked to an increase in oceanic heat supply, which enhances basal melt and thinning of ice shelves. Here we detail the interaction of modified Circumpolar Deep Water (mCDW) with the Amery Ice Shelf, the largest ice shelf in East Antarctica, and provide the first estimates of basal melting due to mCDW. We use subice shelf ocean observations from a borehole site (AM02) situated ∼70 km inshore of the ice shelf front, together with open ocean observations in Prydz Bay. We find that mCDW transport into the cavity is about 0.22 ± 0.06 Sv (1 Sv = 10 6 m 3 s −1 ). The inflow of mCDW drives a net basal melt rate of up to 2 ± 0.5 m yr −1 during 2001 (23.9 ± 6.52 Gt yr −1 from under about 12,800 km 2 of the north‐eastern flank of the ice shelf). The heat content flux by mCDW at AM02 shows high intra‐annual variability (up to 40%). Our results suggest two main modes of subice shelf circulation and basal melt regimes: (1) the “ice pump”/high salinity shelf water circulation, on the western flank and (2) the mCDW meltwater‐driven circulation in conjunction with the “ice pump,” on the eastern flank. These results highlight the sensitivity of the Amery's basal melting to changes in mCDW inflow. Improved understanding of such ice shelf‐ocean interaction is crucial to refining projections of mass loss and associated sea level rise.
Ocean heat drives rapid basal melt of the Totten Ice Shelf
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-12-2016
Abstract: Inflow of warm water drives rapid melt of the Totten Ice Shelf, demonstrating that this sector of East Antarctica is exposed to ocean heat.
Seasonality of Warm Water Intrusions Onto the Continental Shelf Near the Totten Glacier
Publisher: American Geophysical Union (AGU)
Date: 06-2019
DOI: 10.1029/2018JC014634
Spatial Variability of Antarctic Bottom Water in the Australian Antarctic Basin From 2018–2020 Captured by Deep Argo
Publisher: American Geophysical Union (AGU)
Date: 02-12-2020
DOI: 10.1029/2020GL089467
Abstract: There are two varieties of Antarctic Bottom Water present in the Australian Antarctic Basin (AAB): locally produced Adélie Land Bottom Water (ALBW) and distantly produced Ross Sea Bottom Water (RSBW). Between 2014 and 2018, RSBW has rebounded from a multidecade freshening trend. The return of the salty RSBW to the AAB is revealed by six Deep Argo floats that have occupied the region from January of 2018 to March of 2020. The floats depict a zonal variation in temperature and salinity in the bottom waters of the AAB, driven by the inflow of RSBW. A simple Optimum Multiparameter Analysis based on potential temperature and salinity gives a sense of scale to the composition of the bottom waters, which are nearly 80% of the new, salty RSBW in the south‐east corner of the basin by 2019 and generally less than 40% to the west closer to the ALBW outflow region and the abyssal plain.
The Southern Ocean Limb of the Global Deep Overturning Circulation*
Publisher: American Meteorological Society
Date: 2001
Controls on Dense Shelf Water Formation in Four East Antarctic Polynyas
Publisher: American Geophysical Union (AGU)
Date: 29-11-2022
DOI: 10.1029/2022JC018804
Abstract: Coastal polynyas are key formation regions for dense shelf water (DSW) that ultimately contributes to the ventilation of the ocean abyss. However, not all polynyas form DSW. We examine how the physiographic setting, water‐mass distribution and transformation, water column stratification, and sea‐ice production regulate DSW formation in four East Antarctic coastal polynyas. We use a salt budget to estimate the relative contribution of sea‐ice production and lateral advection to the monthly change in salinity in each polynya. DSW forms in Mackenzie polynya due to a combination of physical features (shallow water depth and a broad continental shelf) and high sea‐ice production. Sea‐ice formation begins early (March) in Mackenzie polynya, counteracting fresh advection and establishing a salty mixed layer in autumn that preconditions the water column for deep convection in winter. Sea‐ice production is moderate in the other three polynyas, but saline DSW is not formed (a fresh variety is formed in the Barrier polynya). In the Shackleton polynya, brine rejection during winter is insufficient to overcome the very fresh autumn mixed layer. In Vincennes Bay, a strong inflow of modified Circumpolar Deep Water stratifies the water column, hindering deep convection and DSW formation. Our study highlights that DSW formation in a given polynya depends on a complex combination of factors, some of which may be strongly altered under a changing climate, with potentially important consequences for the ventilation of the deep ocean, the global meridional overturning circulation, and the transport of ocean heat to Antarctic ice shelves.
Regional Changes in Icescape Impact Shelf Circulation and Basal Melting
Publisher: American Geophysical Union (AGU)
Date: 18-11-2017
DOI: 10.1002/2017GL074943
Biological Uptake, Water Mass Mixing and Scavenging Limit the Transport of Manganese‐Rich Waters From the East Antarctic Shelf
Publisher: American Geophysical Union (AGU)
Date: 08-2023
DOI: 10.1029/2022GB007613
Abstract: Manganese (Mn) is an essential element involved in photosynthesis, yet its concentrations in Southern Ocean open waters are very low, arising from biological uptake and limited external inputs. At southern latitudes, waters overlying the Antarctic shelf are expected to have much higher Mn concentrations due to their proximity to external sources. In this study, we investigated the potential export of Mn‐rich Antarctic shelf waters toward depleted open Southern Ocean waters. Our results showed that while high Mn concentrations were observed over the shelf, biological uptake decreased dissolved Mn concentrations in surface waters north of the South Antarctic Circumpolar Current Front ( .1 nmol kg −1 ), limiting its export. Conversely, mixing between Mn‐rich Antarctic Bottom Waters and Mn‐depleted Lower Circumpolar Deep Waters combined with oxidative and scavenging processes led to a decrease in dissolved Mn concentrations within bottom waters, with distance from the coast. Particulate Mn concentrations also showed a decreasing trend with distance from the coast. A comparison with other Antarctic coastal regions suggests this bottom water Mn removal may be widespread and that East Antarctica may be characterized by lower Mn concentrations compared to other regions. Still, subsurface dissolved Mn maxima (0.3–0.6 nmol kg −1 ) represented a potential reservoir for surface waters. We hypothesize that these high subsurface values result from external sources near the shelf. Overall, these results suggest that the moderate lateral export of trace metal‐enriched waters contributes to the extremely low and potentially limiting Mn concentrations previously reported further north in this Southern Ocean region.
Detecting and Characterizing Ekman Currents in the Southern Ocean
Publisher: American Meteorological Society
Date: 05-2015
Abstract: This study presents a unique array of velocity profiles from Electromagnetic Autonomous Profiling Explorer (EM-APEX) profiling floats in the Antarctic Circumpolar Current (ACC) north of Kerguelen. The authors use these profiles to examine the nature of Ekman spirals, formed by the action of the wind on the ocean’s surface, in light of Ekman’s classical linear theory and more recent enhancements. Vertical decay scales of the Ekman spirals were estimated independently from current litude and rotation. Assuming a vertically uniform geostrophic current, decay scales from the Ekman current heading were twice as large as those from the current speed decay, indicating a compressed spiral, consistent with prior observations and violating the classical theory. However, if geostrophic shear is accurately removed, the observed Ekman spiral is as predicted by classical theory and decay scales estimated from litude decay and rotation converge toward a common value. No statistically robust relationship is found between stratification and Ekman decay scales. The results indicate that compressed spirals observed in the Southern Ocean arise from aliasing of depth-varying geostrophic currents into the Ekman spiral, as opposed to surface trapping of Ekman currents associated with stratification, and extends the geographical area of similar results from Drake Passage (Polton et al. 2013). Accounting for this effect, the authors find that constant viscosity Ekman models offer a reasonable description of momentum mixing into the upper ocean in the ACC north of Kerguelen. These results demonstrate the effectiveness of a new method and provide additional evidence that the same processes are active for the entire Southern Ocean.
Hydrothermal Heat Enhances Abyssal Mixing in the Antarctic Circumpolar Current
Publisher: American Geophysical Union (AGU)
Date: 18-01-2019
DOI: 10.1029/2018GL080410
Deep Argo Reveals Bottom Water Properties and Pathways in the Australian‐Antarctic Basin
Publisher: American Geophysical Union (AGU)
Date: 12-2021
DOI: 10.1029/2021JC017935
Abstract: Changes in properties and quantity of Antarctic Bottom Water (AABW) have major implications for the climate system, through sequestration of heat and carbon into, and ventilation of, the abyssal ocean. Yet, it remains one of the most difficult water masses to observe. An array of 12 Deep Argo floats, capable of profiling from the surface to the seafloor and under sea ice, provides a new perspective on AABW in the Australian‐Antarctic Basin. Over 2 years of data from the floats illuminate AABW properties with unprecedented detail, simultaneously s ling AABW at multiple locations, year‐round, throughout the basin. Calibrating each float in idually with nearby, quasi‐simultaneous shipboard profiles ensures the highest quality salinity data, with estimated accuracy of ±0.005 or better. Pathways of Ross Sea and Adélie Land Bottom Water (RSBW and ALBW), defined by their unique temperature and salinity characteristics, are mapped along the continental slope from their respective sources. The main pathway of RSBW, identified by its characteristic deep salinity maximum, is inferred to be inshore of the 3,700 m isobath, where it cools and freshens westward along the slope before interacting with ALBW near 140°E. A pulse of very cold and very fresh (nearly −0.6°C, 34.82 g kg −1 ) ALBW appears in February 2019, highlighting temporal variability on daily scales near its source. Deep Argo has greatly enhanced our view of AABW in the Australian‐Antarctic Basin and will prove to be an essential tool for monitoring future changes in the deep ocean by drastically increasing observations in a cost‐effective way.
Change in Dense Shelf Water and Adélie Land Bottom Water Precipitated by Iceberg Calving
Publisher: American Geophysical Union (AGU)
Date: 08-03-2018
DOI: 10.1002/2017GL076195
Southern Ocean overturning across streamlines in an eddying simulation of the Antarctic Circumpolar Current
Publisher: Copernicus GmbH
Date: 19-12-2007
Abstract: Abstract. An eddying global model is used to study the characteristics of the Antarctic Circumpolar Current (ACC) in a streamline-following framework. Previous model-based estimates of the meridional circulation were calculated using zonal averages: this method leads to a counter-intuitive poleward circulation of the less dense waters, and underestimates the eddy effects. We show that on the contrary, the upper ocean circulation across streamlines agrees with the theoretical view: an equatorward mean flow partially cancelled by a poleward eddy mass flux. Two model simulations, in which the buoyancy forcing above the ACC changes from positive to negative, suggest that the relationship between the residual meridional circulation and the surface buoyancy flux is not as straightforward as assumed by the simplest theoretical models: the sign of the residual circulation cannot be inferred from the surface buoyancy forcing only. Among the other processes that likely play a part in setting the meridional circulation, our model results emphasize the complex three-dimensional structure of the ACC (probably not well accounted for in streamline-averaged, two-dimensional models) and the distinct role of temperature and salinity in the definition of the density field. Heat and salt transports by the time-mean flow are important even across time-mean streamlines. Heat and salt are balanced in the ACC, the model drift being small, but the nonlinearity of the equation of state cannot be ignored in the density balance.
Sensitivity of Antarctic Circumpolar Current Transport and Eddy Activity to Wind Patterns in the Southern Ocean
Publisher: American Meteorological Society
Date: 04-2015
Abstract: The Southern Hemisphere westerly winds have intensified in recent decades associated with a positive trend in the southern annular mode (SAM). However, the response of the Antarctic Circumpolar Current (ACC) transport and eddy field to wind forcing remains a topic of debate. This study uses global eddy-permitting ocean circulation models driven with both idealized and realistic wind forcing to explore the response to interannual wind strengthening. The response of the barotropic and baroclinic transports and eddy field of the ACC is found to depend on the spatial pattern of the changes in wind forcing. In isolation, an enhancement of the westerlies over the ACC belt leads to an increase of both barotropic and baroclinic transport within the ACC envelope, with lagged enhancement of the eddy kinetic energy (EKE). In contrast, an increase in wind forcing near Antarctica drives a largely barotropic change in transport along closed f / H contours (“free mode”), with little change in eddy activity. Under realistic forcing, the interplay of the SAM and the El Niño–Southern Oscillation (ENSO) influences the spatial distribution of the wind anomalies, in particular the partition between changes in the wind stress over the ACC and along f / H contours. This study finds that the occurrence of a negative or positive ENSO during a positive SAM can cancel or double the wind anomalies near Antarctica, altering the response of the ACC and its eddy field. While a negative ENSO and positive SAM favors an increase in EKE, a positive ENSO and positive SAM lead to barotropic transport changes and no eddy response.
Summertime physical and biological controls on O-2 and CO2 in the Australian Sector of the Southern Ocean
Publisher: Elsevier BV
Date: 07-2015
The Diabatic Deacon Cell*
Publisher: American Meteorological Society
Date: 12-2000
Mercury in the Southern Ocean
Publisher: Elsevier BV
Date: 07-2011
Abyssal ocean overturning slowdown and warming driven by Antarctic meltwater
Publisher: Springer Science and Business Media LLC
Date: 29-03-2023
A Continental Shelf Pump for CO2 on the Adélie Land Coast, East Antarctica
Publisher: American Geophysical Union (AGU)
Date: 10-2020
DOI: 10.1029/2020JC016302
Polar research: Six priorities for Antarctic science
Publisher: Springer Science and Business Media LLC
Date: 08-2014
DOI: 10.1038/512023A
Localized subduction of anthropogenic carbon dioxide in the Southern Hemisphere oceans
Publisher: Springer Science and Business Media LLC
Date: 29-07-2012
DOI: 10.1038/NGEO1523
Seasonal Transformation and Spatial Variability of Water Masses Within MacKenzie Polynya, Prydz Bay
Publisher: American Geophysical Union (AGU)
Date: 12-2021
DOI: 10.1029/2021JC017748
Abstract: We provide a detailed description of the spatial distribution, seasonality and transformation of the main water masses within MacKenzie Polynya (MP) in Prydz Bay, East Antarctica, using data from instrumented southern elephant seals. Dense Shelf Water (DSW) formation in MP shows large spatial variability that is related to the (a) local bathymetry, (b) water column preconditioning from the presence/absence of different water masses, and (c) proximity to the Amery Ice Shelf meltwater outflow. MP exhibits sustained sea ice production and brine rejection (thus, salinity increase) from April to October. However, new DSW is only formed from June onward, when the mixed layer deepens and convection is strong enough to break the stratification set by Antarctic Surface Water above and Ice Shelf Water below. We found no evidence of DSW export from MP to Darnley polynya, as previously suggested. Rather, our observations suggest some DSW formed in Darnley Polynya may drain toward the western Prydz Bay. Then, DSW is exported offshore from Prydz Bay through the Prydz Channel. The interplay between sea ice formation, meltwater input, and sea floor topography is likely to explain why some coastal polynyas form more DSW than others, as well as the temporal variability in DSW formation within a particular polynya.
Southern ocean thermocline ventilation
Publisher: American Meteorological Society
Date: 03-2010
Abstract: An approximate mass (volume) budget in the surface layer of the Southern Ocean is used to investigate the intensity and regional variability of the ventilation process, discussed here in terms of subduction and upwelling. Ventilation resulting from Ekman pumping is estimated from satellite winds, the geostrophic mean component is assessed from a climatology strengthened with Argo data, and the eddy-induced advection is included via the parameterization of Gent and McWilliams, together with eddy mixing estimates. All three components contribute significantly to ventilation. Finally, the seasonal cycle of the upper ocean is resolved using Argo data. The circumpolar-averaged circulation shows an upwelling in the Antarctic Intermediate Water (AAIW) density classes, which is carried north into a zone of dense Subantarctic Mode Water (SAMW) subduction. Although no consistent net production is found in the light SAMW density classes, a large subduction of Subtropical Mode Water (STMW) is observed. The STMW area is fed by convergence of a southward and a northward residual meridional circulation. The eddy-induced contribution is important for the water mass transport in the vicinity of the Antartic Circumpolar Current. It balances the horizontal northward Ekman transport as well as the vertical Ekman pumping. While the circumpolar-averaged upper cell structure is consistent with the average surface fluxes, it hides strong longitudinal regional variations and does not represent any local regime. Subduction shows strong regional variability with bathymetrically constrained hotspots of large subduction. These hotspots are consistent with the interior potential vorticity structure and circulation in the thermocline. Pools of SAMW and AAIW of different densities are found along the circumpolar belt in association with the regional pattern of subduction and interior circulation.
Modified Circumpolar Deep Water intrusions in Vincennes Bay, East Antarctica.
Publisher: Wiley
Date: 25-11-2020
Warm Modified Circumpolar Deep Water Intrusions Drive Ice Shelf Melt and Inhibit Dense Shelf Water Formation in Vincennes Bay, East Antarctica
Publisher: American Geophysical Union (AGU)
Date: 30-07-2021
DOI: 10.1029/2020JC016998
Abstract: Antarctic Bottom Water (AABW) production supplies the deep limb of the global overturning circulation and ventilates the deep ocean. While the Weddell and Ross Seas are recognized as key sites for AABW production, additional sources have been discovered in coastal polynya regions around East Antarctica, most recently at Vincennes Bay. Vincennes Bay, despite encompassing two distinct polynya regions, is considered the weakest source, producing Dense Shelf Water (DSW) only just dense enough to contribute to the lighter density classes of AABW found offshore. Here we provide the first detailed oceanographic observations of the continental shelf in Vincennes Bay (104‐111°E), using CTD data from instrumented elephant seals spanning from February to November of 2012. We find that Vincennes Bay has East Antarctica’s warmest recorded intrusions of modified Circumpolar Deep Water (mCDW) and that warm mCDW drives basal melt under Vanderford and Underwood ice shelves. Our study also provides the first direct observational evidence for the inflow of meltwater to this region, which increases stratification and hinders DSW formation, and thus AABW production. The Vincennes Bay glaciers, together with the Totten Glacier, drain part of the Aurora Basin, which holds up to 7 m of sea level rise equivalent. Our results highlight the vulnerability of the East Antarctic Ice Sheet to intrusions of mCDW.
A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization
Publisher: Springer Science and Business Media LLC
Date: 10-2000
DOI: 10.1038/35037500
Abstract: Changes in iron supply to oceanic plankton are thought to have a significant effect on concentrations of atmospheric carbon dioxide by altering rates of carbon sequestration, a theory known as the 'iron hypothesis'. For this reason, it is important to understand the response of pelagic biota to increased iron supply. Here we report the results of a mesoscale iron fertilization experiment in the polar Southern Ocean, where the potential to sequester iron-elevated algal carbon is probably greatest. Increased iron supply led to elevated phytoplankton biomass and rates of photosynthesis in surface waters, causing a large drawdown of carbon dioxide and macronutrients, and elevated dimethyl sulphide levels after 13 days. This drawdown was mostly due to the proliferation of diatom stocks. But downward export of biogenic carbon was not increased. Moreover, satellite observations of this massive bloom 30 days later, suggest that a sufficient proportion of the added iron was retained in surface waters. Our findings demonstrate that iron supply controls phytoplankton growth and community composition during summer in these polar Southern Ocean waters, but the fate of algal carbon remains unknown and depends on the interplay between the processes controlling export, remineralisation and timescales of water mass subduction.
Choosing the future of Antarctica
Publisher: Springer Science and Business Media LLC
Date: 06-2018
DOI: 10.1038/S41586-018-0173-4
Abstract: We present two narratives on the future of Antarctica and the Southern Ocean, from the perspective of an observer looking back from 2070. In the first scenario, greenhouse gas emissions remained unchecked, the climate continued to warm, and the policy response was ineffective this had large ramifications in Antarctica and the Southern Ocean, with worldwide impacts. In the second scenario, ambitious action was taken to limit greenhouse gas emissions and to establish policies that reduced anthropogenic pressure on the environment, slowing the rate of change in Antarctica. Choices made in the next decade will determine what trajectory is realized.
Generation of the Internal Pycnocline in the Subpolar Southern Ocean by Wintertime Sea Ice Melting
Publisher: American Geophysical Union (AGU)
Date: 03-2023
DOI: 10.1029/2022JC019113
Abstract: The ocean's internal pycnocline is a layer of elevated stratification that separates the well‐ventilated upper ocean from the more slowly renewed deep ocean. Despite its pivotal role in organizing ocean circulation, the processes governing the formation of the internal pycnocline remain little understood. Classical theories on pycnocline formation have been couched in terms of temperature and it is not clear how the theory applies in the high‐latitude Southern Ocean, where stratification is dominated by salinity. Here we assess the mechanisms generating the internal pycnocline at southern high latitudes through the analysis of a high‐resolution, realistic, global sea ice–ocean model. We show evidence suggesting that the internal pycnocline's formation is associated with sea ice‐ocean interactions in two distinct ice‐covered regions, fringing the Antarctic continental slope and the winter sea‐ice edge. In both areas, winter‐persistent sea‐ice melt creates strong, salinity‐based stratification at the base of the winter mixed layer. The resulting sheets of high stratification subsequently descend into the ocean interior at fronts of the Antarctic Circumpolar Current, and connect seamlessly to the internal pycnocline in areas further north in which pycnocline stratification is determined by temperature. Our findings thus suggest an important role of localized sea ice‐ocean interactions in configuring the vertical structure of the Southern Ocean.
Glacier tongue calving reduced dense water formation and enhanced carbon uptake
Publisher: American Geophysical Union (AGU)
Date: 13-03-2013
DOI: 10.1002/GRL.50178
Bathymetry‐Constrained Navigation of Argo Floats Under Sea Ice on the Antarctic Continental Shelf
Publisher: American Geophysical Union (AGU)
Date: 27-05-2020
DOI: 10.1029/2020GL087019
Ocean circulation and frontal structure near the southern Kerguelen Plateau: The physical context for the Kerguelen Axis ecosystem study
Publisher: Elsevier BV
Date: 04-2018
Recent reduced abyssal overturning and ventilation in the Australian Antarctic Basin
Publisher: Springer Science and Business Media LLC
Date: 25-05-2023
DOI: 10.1038/S41558-023-01667-8
Abstract: Dense water formed near Antarctica, known as Antarctic bottom water (AABW), drives deep ocean circulation and supplies oxygen to the abyssal ocean. Observations show that AABW has freshened and contracted since the 1960s, yet the drivers of these changes and their impact remain uncertain. Here, using observations from the Australian Antarctic Basin, we show that AABW transport reduced by 4.0 Sv between 1994 and 2009, during a period of strong freshening on the continental shelf. An increase in shelf water salinity between 2009 and 2018, previously linked to transient climate variability, drove a partial recovery (2.2 Sv) of AABW transport. Over the full period (1994 to 2017), the net slowdown of −0.8 ± 0.5 Sv decade −1 thinned well-oxygenated layers, driving deoxygenation of −3 ± 2 μmol kg −1 decade −1 . These findings demonstrate that freshening of Antarctic shelf waters weakens the lower limb of the abyssal overturning circulation and reduces deep ocean oxygen content.
Estimates of Area-Averaged Diapycnal Fluxes from Basin-Scale Budgets
Publisher: American Meteorological Society
Date: 09-2000
Brief communication: Impacts of a developing polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg B09B
Publisher: Copernicus GmbH
Date: 04-11-2016
Abstract: Abstract. The dramatic calving of the Mertz Glacier tongue in 2010, precipitated by the movement of iceberg B09B, reshaped the oceanographic regime across the Mertz Polynya and Commonwealth Bay, regions where high-salinity shelf water (HSSW) – the precursor to Antarctic bottom water (AABW) – is formed. Here we present post-calving observations that suggest that this reconfiguration and subsequent grounding of B09B have driven the development of a new polynya and associated HSSW production off Commonwealth Bay. Supported by satellite observations and modelling, our findings demonstrate how local icescape changes may impact the formation of HSSW, with potential implications for large-scale ocean circulation.
Rapid response of the East Australian Current to remote wind forcing: The role of barotropic-baroclinic interactions
Publisher: Journal of Marine Research/Yale
Date: 05-2010
Circulation, Renewal, and Modification of Antarctic Mode and Intermediate Water*
Publisher: American Meteorological Society
Date: 04-2001
Recent recovery of Antarctic Bottom Water formation in the Ross Sea driven by climate anomalies
Publisher: Springer Science and Business Media LLC
Date: 16-11-2020
State of the Climate in 2015
Publisher: American Meteorological Society
Date: 08-2016
DOI: 10.1175/2016BAMSSTATEOFTHECLIMATE.1
Abstract: Editor’s note: For easy download the posted pdf of the State of the Climate for 2016 is a very low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
Changes in water properties and flow regime on the continental shelf off the A délie/G eorge V L and coast, E ast A ntarctica, after glacier
Publisher: American Geophysical Union (AGU)
Date: 08-2017
DOI: 10.1002/2017JC012925
Strong export of Antarctic Bottom Water east of the Kerguelen plateau
Publisher: Springer Science and Business Media LLC
Date: 25-04-2010
DOI: 10.1038/NGEO842
Regional circulation and its impact on upper ocean variability south of Tasmania
Publisher: Elsevier BV
Date: 11-2011
Biological uptake, water mass mixing and scavenging prevent transport of manganese-rich waters from the Antarctic shelf
Publisher: Wiley
Date: 27-10-2022
Freshening drives contraction of Antarctic Bottom Water in the Australian Antarctic Basin
Publisher: American Geophysical Union (AGU)
Date: 12-03-2014
DOI: 10.1002/2013GL058921
Formation and export of dense shelf water from the Adélie Depression, East Antarctica
Publisher: American Geophysical Union (AGU)
Date: 04-2008
DOI: 10.1029/2007JC004346
The Dynamics of Southern Ocean Storm Tracks
Publisher: American Meteorological Society
Date: 03-2015
Abstract: The mechanisms that initiate and maintain oceanic “storm tracks” (regions of anomalously high eddy kinetic energy) are studied in a wind-driven, isopycnal, primitive equation model with idealized bottom topography. Storm tracks are found downstream of the topography in regions strongly influenced by a large-scale stationary meander that is generated by the interaction between the background mean flow and the topography. In oceanic storm tracks the length scale of the stationary meander differs from that of the transient eddies, a point of distinction from the atmospheric storm tracks. When the zonal length and height of the topography are varied, the storm-track intensity is largely unchanged and the downstream storm-track length varies only weakly. The dynamics of the storm track in this idealized configuration are investigated using a wave activity flux (related to the Eliassen–Palm flux and eddy energy budgets). It is found that vertical fluxes of wave activity (which correspond to eddy growth by baroclinic conversion) are localized to the region influenced by the standing meander. Farther downstream, organized horizontal wave activity fluxes (which indicate eddy energy fluxes) are found. A mechanism for the development of oceanic storm tracks is proposed: the standing meander initiates localized conversion of energy from the mean field to the eddy field, while the storm track develops downstream of the initial baroclinic growth through the ageostrophic flux of Montgomery potential. Finally, the implications of this analysis for the parameterization and prediction of storm tracks in ocean models are discussed.
Barotropic and baroclinic contributions to along-stream and across-stream transport in the Antarctic Circumpolar Current
Publisher: American Geophysical Union (AGU)
Date: 11-2014
DOI: 10.1002/2014JC010020
Carbon uptake and biogeochemical change in the Southern Ocean, south of Tasmania
Publisher: Copernicus GmbH
Date: 21-11-2017
Abstract: Abstract. Biogeochemical change in the water masses of the Southern Ocean, south of Tasmania, was assessed for the 16-year period between 1995 and 2011 using data from four summer repeats of the WOCE–JGOFS–CLIVAR–GO-SHIP (Key et al., 2015 Olsen et al., 2016) SR03 hydrographic section (at ∼ 140° E). Changes in temperature, salinity, oxygen, and nutrients were used to disentangle the effect of solubility, biology, circulation and anthropogenic carbon (CANT) uptake on the variability of dissolved inorganic carbon (DIC) for eight water mass layers defined by neutral surfaces (γn). CANT was estimated using an improved back-calculation method. Warming (∼ 0.0352 ± 0.0170 °C yr−1) of Subtropical Central Water (STCW) and Antarctic Surface Water (AASW) layers decreased their gas solubility, and accordingly DIC concentrations increased less rapidly than expected from equilibration with rising atmospheric CO2 (∼ 0.86 ± 0.16 µmol kg−1 yr−1 versus ∼ 1 ± 0.12 µmol kg−1 yr−1). An increase in apparent oxygen utilisation (AOU) occurred in these layers due to either remineralisation of organic matter or intensification of upwelling. The range of estimates for the increases in CANT were 0.71 ± 0.08 to 0.93 ± 0.08 µmol kg−1 yr−1 for STCW and 0.35 ± 0.14 to 0.65 ± 0.21 µmol kg−1 yr−1 for AASW, with the lower values in each water mass obtained by assigning all the AOU change to remineralisation. DIC increases in the Sub-Antarctic Mode Water (SAMW, 1.10 ± 0.14 µmol kg−1 yr−1) and Antarctic Intermediate Water (AAIW, 0.40 ± 0.15 µmol kg−1 yr−1) layers were similar to the calculated CANT trends. For SAMW, the CANT increase tracked rising atmospheric CO2. As a consequence of the general DIC increase, decreases in total pH (pHT) and aragonite saturation (ΩAr) were found in most water masses, with the upper ocean and the SAMW layer presenting the largest trends for pHT decrease (∼ −0.0031 ± 0.0004 yr−1). DIC increases in deep and bottom layers (∼ 0.24 ± 0.04 µmol kg−1 yr−1) resulted from the advection of old deep waters to resupply increased upwelling, as corroborated by increasing silicate (∼ 0.21 ± 0.07 µmol kg−1 yr−1), which also reached the upper layers near the Antarctic Divergence (∼ 0.36 ± 0.06 µmol kg−1 yr−1) and was accompanied by an increase in salinity. The observed changes in DIC over the 16-year span caused a shoaling (∼ 340 m) of the aragonite saturation depth (ASD, ΩAr = 1) within Upper Circumpolar Deep Water that followed the upwelling path of this layer. From all our results, we conclude a scenario of increased transport of deep waters into the section and enhanced upwelling at high latitudes for the period between 1995 and 2011 linked to strong westerly winds. Although enhanced upwelling lowered the capacity of the AASW layer to uptake atmospheric CO2, it did not limit that of the newly forming SAMW and AAIW, which exhibited CANT storage rates (∼ 0.41 ± 0.20 mol m−2 yr−1) twice that of the upper layers.
The Neodymium Isotope Fingerprint of Adélie Coast Bottom Water
Publisher: American Geophysical Union (AGU)
Date: 16-10-2018
DOI: 10.1029/2018GL080074
Abstract: Adélie Land Bottom Water (ALBW), a variety of Antarctic Bottom Water formed off the Adélie Land coast of East Antarctica, ventilates the abyssal layers of the Australian sector of the Southern Ocean as well as the eastern Indian and Pacific Oceans. We present the first dissolved neodymium (Nd) isotope and concentration measurements for ALBW. The summertime signature of ALBW is characterized by ε Nd = −8.9, distinct from Ross Sea Bottom Water, and similar to Weddell Sea Bottom Water. Adélie Land Shelf Water, the precursor water mass for wintertime ALBW, features the least radiogenic Nd fingerprint observed around Antarctica to date (ε Nd = −9.9). Local geology around Antarctica is important in setting the chemical signature of in idual varieties of Antarctic Bottom Water, evident from the shelf water signature, which should be considered in the absence of direct wintertime observations.
Relative g-factor measurements in the stable Te isotopes
Publisher: American Physical Society (APS)
Date: 06-09-2007
Controls on circulation, cross-shelf exchange, and dense water formation in an Antarctic polynya
Publisher: American Geophysical Union (AGU)
Date: 08-07-2016
DOI: 10.1002/2016GL069479
Stationary Rossby Waves Dominate Subduction of Anthropogenic Carbon in the Southern Ocean
Publisher: Springer Science and Business Media LLC
Date: 06-12-2017
DOI: 10.1038/S41598-017-17292-3
Abstract: The Southern Ocean has taken up more than 40% of the total anthropogenic carbon (C ant ) stored in the oceans since the preindustrial era, mainly in subantarctic mode and intermediate waters (SAMW-AAIW). However, the physical mechanisms responsible for the transfer of C ant into the ocean interior remain poorly understood. Here, we use high resolution (1/10°) ocean simulations to investigate these mechanisms at the SAMW-AAIW subduction hotspots. Mesoscale Stationary Rossby Waves (SRWs), generated where the Antarctic Circumpolar Current interacts with topography, make the dominant contribution to the C ant transfer in SAMW-AAIW in the Indian and Pacific sectors (66% and 95% respectively). Eddy-resolving simulations reproduce the observed C ant sequestration in these layers, while lower spatial resolution models, that do not reproduce SRWs, underestimate the inventory of C ant in these layers by 40% and overestimate the storage in denser layers. A key implication is that climate model simulations, that lack sufficient resolution to represent sequestration by SRWs, are therefore likely to overestimate the residence time of C ant in the ocean, with implications for simulated rates of climate change.
Subantarctic mode water: Distribution and circulation
Publisher: Springer Science and Business Media LLC
Date: 11-11-2011
Southern Ocean frontal structure and sea-ice formation rates revealed by elephant seals
Publisher: Proceedings of the National Academy of Sciences
Date: 19-08-2008
Abstract: Polar regions are particularly sensitive to climate change, with the potential for significant feedbacks between ocean circulation, sea ice, and the ocean carbon cycle. However, the difficulty in obtaining in situ data means that our ability to detect and interpret change is very limited, especially in the Southern Ocean, where the ocean beneath the sea ice remains almost entirely unobserved and the rate of sea-ice formation is poorly known. Here, we show that southern elephant seals ( Mirounga leonina ) equipped with oceanographic sensors can measure ocean structure and water mass changes in regions and seasons rarely observed with traditional oceanographic platforms. In particular, seals provided a 30-fold increase in hydrographic profiles from the sea-ice zone, allowing the major fronts to be mapped south of 60°S and sea-ice formation rates to be inferred from changes in upper ocean salinity. Sea-ice production rates peaked in early winter (April–May) during the rapid northward expansion of the pack ice and declined by a factor of 2 to 3 between May and August, in agreement with a three-dimensional coupled ocean–sea-ice model. By measuring the high-latitude ocean during winter, elephant seals fill a “blind spot” in our s ling coverage, enabling the establishment of a truly global ocean-observing system.
Ocean-ice shelf interaction in East Antarctica
Publisher: The Oceanography Society
Date: 12-2016
Generation of the Southern Ocean pycnocline by sea ice-ocean interactions
Publisher: Wiley
Date: 14-02-2022
Freshening by glacial meltwater enhances melting of ice shelves and reduces formation of Antarctic Bottom Water
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-04-2018
Abstract: Glacial meltwater stops bottom-water formation, allowing warm ocean waters to reach Antarctic ice shelves and drive rapid melting.
Along‐Slope Variability of Cross‐Slope Eddy Transport in East Antarctica
Publisher: American Geophysical Union (AGU)
Date: 24-07-2019
DOI: 10.1029/2019GL082999
Abstract: Circumpolar Deep Water (CDW) transport across the Antarctic continental slope regulates the delivery of heat to the shelf and its availability to melt floating ice shelves. The cross‐slope density field, calculated from profiles collected by conductivity‐temperature‐depth‐tagged marine mammals on the East Antarctic slope (0–160°E, above 1,000‐ to 3,000‐m isobaths), indicates eddy‐driven overturning: onshore transport of CDW and offshore transport of shallower Antarctic Surface Water. Enhanced eddy activity, determined by a spice standard deviation threshold in the CDW layer, is present over about a third of the East Antarctic slope analyzed. Significantly stronger CDW transport in regions of elevated spice variability produces subsurface temperature anomalies of 0.2–0.25 °C relative to the East Antarctic average. Estimating eddy diffusivity from the hydrography yields about 0.8 m 2 /s of warm CDW transport to the shelf break in high‐variability regions. Variability of eddy‐induced CDW transport influences the reservoir of heat available for transport across the shelf break.
Sea Ice Meltwater and Circumpolar Deep Water Drive Contrasting Productivity in Three Antarctic Polynyas
Publisher: American Geophysical Union (AGU)
Date: 05-2019
DOI: 10.1029/2019JC015071
Residence Time and Transformation of Warm Circumpolar Deep Water on the Antarctic Continental Shelf
Publisher: American Geophysical Union (AGU)
Date: 19-10-2021
DOI: 10.1029/2021GL096092
Abstract: Inflow of warm modified Circumpolar Deep Water (CDW) onto the Antarctic continental shelf and into ice shelf cavities is a key driver of Antarctic ice shelf mass loss. While recent research has advanced understanding of CDW heat transport onto the continental shelf, the fate of CDW on the shelf is less understood. Here, we use Lagrangian particle tracking in an ocean‐sea ice model without ice shelf cavities to map the residence time of CDW on the Antarctic continental shelf. Mean residence times vary from 1 month in the East Antarctic to 1 year in the West Antarctic. In regions of dense water formation, transformation of CDW on the shelf limits access of CDW to ice shelves, despite strong onshore CDW heat transport. Elsewhere transformation of CDW on the shelf is weak, implying that temperature on the shelf is limited by heat transport onto the shelf or the offshore heat reservoir.
On-shelf circulation of warm water toward the Totten Ice Shelf in East Antarctica
Publisher: Springer Science and Business Media LLC
Date: 17-08-2023
DOI: 10.1038/S41467-023-39764-Z
Abstract: The Totten Glacier in East Antarctica, with an ice volume equivalent to .5 m of global sea-level rise, is grounded below sea level and, therefore, vulnerable to ocean forcing. Here, we use bathymetric and oceanographic observations from previously uns led parts of the Totten continental shelf to reveal on-shelf warm water pathways defined by deep topographic features. Access of warm water to the Totten Ice Shelf (TIS) cavity is facilitated by a deep shelf break, a broad and deep depression on the shelf, a cyclonic circulation that carries warm water to the inner shelf, and deep troughs that provide direct access to the TIS cavity. The temperature of the warmest water reaching the TIS cavity varies by ~0.8 °C on an interannual timescale. Numerical simulations constrained by the updated bathymetry demonstrate that the deep troughs play a critical role in regulating ocean heat transport to the TIS cavity and the subsequent basal melt of the ice shelf.
Distribution of water masses and meltwater on the continental shelf near the Totten and Moscow University ice shelves
Publisher: American Geophysical Union (AGU)
Date: 03-2017
DOI: 10.1002/2016JC012115
Related Organisations
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Related Funding Activities
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