Warm modified Circumpolar Deep Water intrusions drive ice shelf melt and inhibit Dense Shelf Water formation in Vincennes Bay, East Antarctica

AbstractPine Island Ice Shelf, in the Amundsen Sea, is losing mass because of warm ocean waters melting the ice from below. Tracing meltwater pathways from ice shelves is important for identifying the regions most affected by the increased input of this water type. Here, optimum multiparameter analysis is used to deduce glacial meltwater fractions from water mass characteristics (temperature, salinity, and dissolved oxygen concentrations), collected during a ship-based campaign in the eastern Amundsen Sea in February–March 2014. Using a one-dimensional ocean model, processes such as variability in the characteristics of the source water masses on shelf and biological productivity/respiration are shown to affect the calculated apparent meltwater fractions. These processes can result in a false meltwater signature, creating misleading apparent glacial meltwater pathways. An alternative glacial meltwater calculation is suggested, using a pseudo–Circumpolar Deep Water endpoint and using an artificial increase in uncertainty of the dissolved oxygen measurements. The pseudo–Circumpolar Deep Water characteristics are affected by the under ice shelf bathymetry. The glacial meltwater fractions reveal a pathway for 2014 meltwater leading to the west of Pine Island Ice Shelf, along the coastline.

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Sensitivity of Circumpolar Deep Water Transport and Ice Shelf Basal Melt along the West Antarctic Peninsula to Changes in the Winds

Journal of Climate ◽

10.1175/jcli-d-11-00307.1 ◽

2012 ◽

Vol 25 (14) ◽

pp. 4799-4816 ◽

Cited By ~ 82

Author(s):

Michael S. Dinniman ◽

John M. Klinck ◽

Eileen E. Hofmann

Keyword(s):

Continental Shelf ◽

Antarctic Peninsula ◽

Deep Water ◽

Constant Factor ◽

Ice Shelf ◽

The West ◽

Ice Shelves ◽

Circumpolar Deep Water ◽

West Antarctic ◽

West Antarctic Peninsula

Abstract Circumpolar Deep Water (CDW) can be found near the continental shelf break around most of Antarctica. Advection of this relatively warm water (up to 2°C) across the continental shelf to the base of floating ice shelves is thought to be a critical source of heat for basal melting in some locations. A high-resolution (4 km) regional ocean–sea ice–ice shelf model of the west Antarctic Peninsula (WAP) coastal ocean was used to examine the effects of changes in the winds on across-shelf CDW transport and ice shelf basal melt. Increases and decreases in the strength of the wind fields were simulated by scaling the present-day winds by a constant factor. Additional simulations considered effects of increased Antarctic Circumpolar Current (ACC) transport. Increased wind strength and ACC transport increased the amount of CDW transported onto the WAP continental shelf but did not necessarily increase CDW flux underneath the nearby ice shelves. The basal melt underneath some of the deeper ice shelves actually decreased with increased wind strength. Increased mixing over the WAP shelf due to stronger winds removed more heat from the deeper shelf waters than the additional heat gained from increased CDW volume transport. The simulation results suggest that the effect on the WAP ice shelves of the projected strengthening of the polar westerlies is not a simple matter of increased winds causing increased (or decreased) basal melt. A simple budget calculation indicated that iron associated with increased vertical mixing of CDW could significantly affect biological productivity of this region.

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On the Modified Circumpolar Deep Water Upwelling Over the Four Ladies Bank in Prydz Bay, East Antarctica

Journal of Geophysical Research Oceans ◽

10.1029/2018jc014026 ◽

2018 ◽

Vol 123 (11) ◽

pp. 7819-7838 ◽

Cited By ~ 6

Author(s):

Chengyan Liu ◽

Zhaomin Wang ◽

Chen Cheng ◽

Yang Wu ◽

Ruibin Xia ◽

...

Keyword(s):

Deep Water ◽

East Antarctica ◽

Prydz Bay ◽

Circumpolar Deep Water

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Late Holocene advance of the Müller Ice Shelf, Antarctic Peninsula: sedimentological, geochemical and palaeontological evidence

Antarctic Science ◽

10.1017/s0954102095000228 ◽

1995 ◽

Vol 7 (2) ◽

pp. 159-170 ◽

Cited By ~ 71

Author(s):

Eugene W. Domack ◽

Scott E. Ishman ◽

Andrew B. Stein ◽

Charles E. McClennen ◽

A.J. Timothy Jull

Keyword(s):

Antarctic Peninsula ◽

Deep Water ◽

Sediment Cores ◽

Austral Summer ◽

Ice Age ◽

Geochemical Data ◽

Organic Carbon Content ◽

Ice Shelf ◽

Circumpolar Deep Water ◽

The Antarctic

Marine sediment cores were obtained from in front of the Müller Ice Shelf in Lallemand Fjord, Antarctic Peninsula in the austral summer of 1990–91. Sedimentological and geochemical data from these cores document a warm period that preceded the advance of the Müller Ice Shelf into Lallemand Fjord. The advance of the ice shelf is inferred from a reduction in the total organic carbon content and an increase in well-sorted, aeolian, sand in cores proximal to the present calving line. This sedimentological change is paralleled by a change in the foraminiferal assemblages within the cores. Advance of the ice shelf is indicated by a shift from assemblages dominated by calcareous benthic and planktonic forms to those dominated by agglutinated forms. A 14C chronology for the cores indicates that the advance of the Müller Ice Shelf took place c. 400 years ago, coincident with glacier advances in other high southern latitude sites during the onset of the Little Ice Age. Ice core evidence, however, documents this period as one of warmer temperatures for the Antarctic Peninsula. We suggest that the ice shelf advance was linked to the exclusion of circumpolar deep water from the fjord. This contributed to increased mass balance of the ice shelf system by preventing the rapid undermelt that is today associated with warm circumpolar deep water within the fjord. We also document the recent retreat of the calving line of the Müller Ice Shelf that is apparently in response to a recent (four decade long) warming trend along the western side of the Antarctic Peninsula.

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Water masses’ bacterial community structure and microbial activities in the Ross Sea, Antarctica

Antarctic Science ◽

10.1017/s0954102010000192 ◽

2010 ◽

Vol 22 (4) ◽

pp. 361-370 ◽

Cited By ~ 12

Author(s):

Mauro Celussi ◽

Andrea Bergamasco ◽

Bruno Cataletto ◽

Serena Fonda Umani ◽

Paola Del Negro

Keyword(s):

Community Structure ◽

Bacterial Community ◽

Deep Water ◽

Bacterial Community Structure ◽

Sea Water ◽

Ross Sea ◽

Water Masses ◽

Shelf Water ◽

Microbial Activities ◽

Ice Shelf

AbstractDuring the summer 2005/06, an oceanographic cruise was carried out in the Ross Sea, from Cape Adare, through the Terra Nova Bay polynya to the eastern edge of the Ross Ice Shelf. We analysed microbial activities (prokaryotic carbon production, protease, phosphatase, beta-glucosidase and lipase activity) and bacterial community structure (using Denaturing Gradient Gel Electrophoresis - DGGE) in order to establish if differences in bacterioplankton assemblages and their metabolic requirements occur within the five Ross Sea water masses: Antarctic Surface Waters (AASW), High Salinity Shelf Water (HSSW), Ice Shelf Water (ISW), Antarctic Bottom Water (AABW), Circumpolar Deep Water (CDW). Differences in activities were found between the highly active AASW and all the other water bodies. A Principal Component Analysis highlighted two main gradients: in the Cape Adare area (AASWn, CDW and AABW) higher phosphatase, lipase and glycolytic activities, increasing towards the surface, were identified, whereas in the southern sector of the basin [AASWs and (m)HSSW] higher leucine uptake and polypeptide degradation characterized the second gradient. DGGE fingerprinting showed for the first time that different water masses harboured diverse bacterial communities, highlighting the high specificity of deep water assemblages.Alpha- andGammaproteobacteriarepresented the main phylogenetic groupings in all samples and no substantial difference in the phylogenetic composition of assemblages was found between different water masses.

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Modeling ice shelf water overflow and bottom water formation in the southern Weddell Sea

Journal of Geophysical Research Atmospheres ◽

10.1029/2009jc005841 ◽

2010 ◽

Vol 115 (C10) ◽

Cited By ~ 12

Author(s):

Yoshimasa Matsumura ◽

Hiroyasu Hasumi

Keyword(s):

Bottom Water ◽

Weddell Sea ◽

Shelf Water ◽

Ice Shelf ◽

Water Formation ◽

Ice Shelf Water ◽

Bottom Water Formation ◽

Water Overflow

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Modified Circumpolar Deep Water intrusions in Vincennes Bay, East Antarctica.

10.1002/essoar.10504957.1 ◽

2020 ◽

Author(s):

Natalia Ribeiro ◽

Laura Herraiz-Borreguero ◽

Stephen R. Rintoul ◽

Clive R. McMahon ◽

Mark Hindell ◽

...

Keyword(s):

Deep Water ◽

East Antarctica ◽

Circumpolar Deep Water

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Water masses distribution offshore the Sabrina Coast (East Antarctica)

Earth System Science Data ◽

10.5194/essd-14-65-2022 ◽

2022 ◽

Vol 14 (1) ◽

pp. 65-78

Author(s):

Manuel Bensi ◽

Vedrana Kovačević ◽

Federica Donda ◽

Philip Edward O'Brien ◽

Linda Armbrecht ◽

...

Keyword(s):

Deep Water ◽

Potential Temperature ◽

Austral Summer ◽

Water Masses ◽

East Antarctica ◽

Ocean Dynamics ◽

Mixing Processes ◽

Circumpolar Deep Water ◽

Oceanographic Data ◽

The Antarctic

Abstract. Current glacier melt rates in West Antarctica substantially exceed those around the East Antarctic margin. The exception is Wilkes Land, where for example Totten Glacier underwent significant retreat between 2000 and 2012, underlining its sensitivity to climate change. This process is strongly influenced by ocean dynamics, which in turn changes in accordance with the evolution of the ice caps. Here, we present new oceanographic data (temperature, salinity, and dissolved oxygen) collected during austral summer 2017 offshore the Sabrina Coast (East Antarctica) from the continental shelf break to ca 3000 m depth. This area is characterized by very few oceanographic in situ observations. The main water masses of the study area, identified by analysing thermohaline properties, are the Antarctic Surface Water with potential temperature θ>-1.5 ∘C and salinity S<34.2 (σθ<27.55 kg m−3), the Winter Water with -1.92<θ<-1.75 ∘C and 34.0<S<34.5 (potential density, 27.55<σθ<27.7 kg m−3), the modified Circumpolar Deep Water with θ>0 ∘C and S>34.5 (σθ>27.7 kg m−3), and Antarctic Bottom Water with -0.50<θ<0 ∘C and 34.63<S<34.67 (27.83<σθ<27.85; neutral density γn>28.30 kg m−3). The latter is a mixture of dense waters from the Ross Sea and Adélie Land continental shelves. Such waters are influenced by the mixing processes they undergo as they move westward along the Antarctic margin, also interacting with the warmer Circumpolar Deep Water. The spatial distribution of water masses offshore the Sabrina Coast also appears to be strongly linked with the complex morpho-bathymetry of the slope and rise area, supporting the hypothesis that downslope processes contribute to shaping the architecture of the distal portion of the continental margin. Oceanographic data presented here can be downloaded from https://doi.org/10.25919/yyex-t381 (CSIRO; Van Graas, 2021).

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