Detailed Seismic Bathymetry Beneath Ekström Ice Shelf, Antarctica: Implications for Glacial History and Ice‐Ocean Interaction

Smith, Emma C.; Hattermann, Tore; Kuhn, Gerhard; Gaedicke, Christoph; Berger, Sophie; Drews, Reinhard; Ehlers, Todd A.; Franke, Dieter; Gromig, Raphael; Hofstede, Coen; Lambrecht, Astrid; Läufer, Andreas; Mayer, Christoph; Tiedemann, Ralf; Wilhelms, Frank; Eisen, Olaf

doi:10.1029/2019gl086187

Cited by 21 publications

(17 citation statements)

References 52 publications

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“…However, the fast-ice thickness still increases in spring and even during austral summer months (albeit very slowly). This can be explained by the measurement uncertainty with respect to the large spatial variability of sea-ice thickness even on very small (centimeter) scales, but the consistency in the data suggests that it could also be caused by consolidation processes within the platelet layer below, i.e., in situ sea-ice growth by heat transport into a supercooled plume residing right beneath the solid fast ice similar to observations in McMurdo Sound (Smith et al, 2012;Leonard et al, 2011;Dempsey et al, 2010;Robinson et al, 2014). So far, in Atka Bay there is only evidence that platelets grow quite large already while still suspended in the water column (Hoppmann et al, 2015b).…”

Section: Seasonal and Interannual Variability Of Snow Depth And Sea-imentioning

confidence: 55%

“…In that respect, Hoppmann et al (2015b) used a subset of oceanographic data collected by the nearby PALAOA hydrographic observatory (Boebel et al, 2006) to link fast-ice observations to ocean properties. A more recent study by Smith et al (2020) helped to constrain the boundary conditions for Ice Shelf Water outflow by mapping in great detail the cavity geometry of the Ekström Ice Shelf. This study also shows data from repeated CTD casts through a borehole in the ice shelf, revealing the buoyant outflow of Ice Shelf Water (ISW) in a relatively shallow surface layer.…”

Section: Spatial Variability Of Fast-ice Properties Related Tomentioning

confidence: 99%

“…Atka Bay is flanked towards the east, south, and west by the edges of the ice shelf, which rise as high as 20 m above sea level. The cavity geometry of the Ekström Ice Shelf is one of the best known in Antarctica (Smith et al, 2020). Atka Bay is seasonally sea-ice covered, and the water depth ranges between 80 and 275 m with maximum depth in the central bay (Kipfstuhl, 1991).…”

Section: Introductionmentioning

confidence: 99%

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Seasonal and interannual variability of landfast sea ice in Atka Bay, Weddell Sea, Antarctica

et al. 2020

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Abstract. Landfast sea ice (fast ice) attached to Antarctic (near-)coastal elements is a critical component of the local physical and ecological systems. Through its direct coupling with the atmosphere and ocean, fast-ice properties are also a potential indicator of processes related to a changing climate. However, in situ fast-ice observations in Antarctica are extremely sparse because of logistical challenges and harsh environmental conditions. Since 2010, a monitoring program observing the seasonal evolution of fast ice in Atka Bay has been conducted as part of the Antarctic Fast Ice Network (AFIN). The bay is located on the northeastern edge of Ekström Ice Shelf in the eastern Weddell Sea, close to the German wintering station Neumayer III. A number of sampling sites have been regularly revisited each year between annual ice formation and breakup to obtain a continuous record of sea-ice and sub-ice platelet-layer thickness, as well as snow depth and freeboard across the bay. Here, we present the time series of these measurements over the last 9 years. Combining them with observations from the nearby Neumayer III meteorological observatory as well as auxiliary satellite images enables us to relate the seasonal and interannual fast-ice cycle to the factors that influence their evolution. On average, the annual consolidated fast-ice thickness at the end of the growth season is about 2 m, with a loose platelet layer of 4 m thickness beneath and 0.70 m thick snow on top. Results highlight the predominately seasonal character of the fast-ice regime in Atka Bay without a significant interannual trend in any of the observed variables over the 9-year observation period. Also, no changes are evident when comparing with sporadic measurements in the 1980s and 1990s. It is shown that strong easterly winds in the area govern the year-round snow distribution and also trigger the breakup of fast ice in the bay during summer months. Due to the substantial snow accumulation on the fast ice, a characteristic feature is frequent negative freeboard, associated flooding of the snow–ice interface, and a likely subsequent snow ice formation. The buoyant platelet layer beneath negates the snow weight to some extent, but snow thermodynamics is identified as the main driver of the energy and mass budgets for the fast-ice cover in Atka Bay. The new knowledge of the seasonal and interannual variability of fast-ice properties from the present study helps to improve our understanding of interactions between atmosphere, fast ice, ocean, and ice shelves in one of the key regions of Antarctica and calls for intensified multidisciplinary studies in this region.

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Section: Seasonal and Interannual Variability Of Snow Depth And Sea-imentioning

confidence: 55%

Section: Spatial Variability Of Fast-ice Properties Related Tomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Seasonal and interannual variability of landfast sea ice in Atka Bay, Weddell Sea, Antarctica

et al. 2020

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“…Both projects collected coincident gravity, magnetic, and radio echo sounding (RES) data ( Figure 1b). Seismic data are incorporated for Ekström (Smith et al, 2020) and Fimbul ice shelves (Nøst, 2004).…”

Section: Methodsmentioning

confidence: 99%

Bathymetry Beneath Ice Shelves of Western Dronning Maud Land, East Antarctica, and Implications on Ice Shelf Stability

Eisermann

Eagles

Ruppel

et al. 2020

Geophysical Research Letters

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Antarctica's ice shelves play a key role in stabilizing the ice streams that feed them. Since basal melting largely depends on ice-ocean interactions, it is vital to attain consistent bathymetry models to estimate water and heat exchange beneath ice shelves. We have constructed bathymetry models beneath the ice shelves of western Dronning Maud Land by inverting airborne gravity data and incorporating seismic, multibeam, and radar depth references. Our models reveal deep glacial troughs beneath the ice shelves and terminal moraines close to the continental shelf breaks, which currently limit the entry of Warm Deep Water from the Southern Ocean. The ice shelves buttress a catchment that comprises an ice volume equivalent to nearly 1 m of eustatic sea level rise, partly susceptible to ocean forcing. Changes in water temperature and thermocline depth may accelerate marine-based ice sheet drainage and constitute an underestimated contribution to future global sea level rise. Plain Language Summary The grounded ice sheets of Antarctica are stabilized by floating ice shelves. Any loss in ice shelf mass is matched by an increase in ice sheet drainage, which contributes to rising sea level. The ice shelves of western Dronning Maud Land are currently in balance with an inland ice volume that has the potential to raise global sea level by nearly 1 m. Ice shelves lose most of their mass from their bases when warm water intrudes from the surrounding ocean. The extent to which this occurs depends on the depth and shape of the seafloor beneath the ice shelves. We have modeled water depths beneath the ice shelves of Dronning Maud Land using airborne gravity data and depth measurements from seismic, multibeam, and radar data. Our bathymetric models show deep troughs beneath the ice shelves and shallow sills close to the continental shelf. These sills currently limit water mass exchange with Warm Deep Water from the Southern Ocean and so protect the ice shelves from significant melting at their bases. A changing climate with increasing ocean temperatures or a shallowing of warm water masses may increase ice shelf melting and lead to an increased sea level contribution.

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“…The ice shelf has passive shelf ice extending from the calving front to the middle of the ice shelf and is supported by the two promontories that buttress the shelf upstream. The bathymetry underneath has a deep inland-sloping trough reaching 1100 m below sea level near the current grounding zone (Smith and others, 2020). This trough extends from the calving front to the grounding zone, but oceanographic measurements from the same study, performed in the shallow regions of the ice shelf cavity showed no signs of warm sea water in the trough.…”

Section: The Dml and Enderby Land Coastsmentioning

confidence: 99%

Characteristics of ice rises and ice rumples in Dronning Maud Land and Enderby Land, Antarctica

et al. 2020

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Ice rises and rumples, locally grounded features adjacent to ice shelves, are relatively small yet play significant roles in Antarctic ice dynamics. Their roles generally depend upon their location within the ice shelf and the stage of the ice-sheet retreat or advance. Large, long-stable ice rises can be excellent sites for deep ice coring and paleoclimate study of the Antarctic coast and the Southern Ocean, while small ice rises tend to respond more promptly and can be used to reveal recent changes in regional mass balance. The coasts of Dronning Maud Land (DML) and Enderby Land in East Antarctica are abundant with these features. Here we review existing knowledge, presenting an up-to-date status of research in these regions with focus on ice rises and rumples. We use regional datasets (satellite imagery, surface mass balance and ice thickness) to analyze the extent and surface morphology of ice shelves and characteristic timescales of ice rises. We find that large parts of DML have been changing over the past several millennia. Based on our findings, we highlight ice rises suitable for drilling ice cores for paleoclimate studies as well as ice rises suitable for deciphering ice dynamics and evolution in the region.

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Detailed Seismic Bathymetry Beneath Ekström Ice Shelf, Antarctica: Implications for Glacial History and Ice‐Ocean Interaction

Cited by 21 publications

References 52 publications

Seasonal and interannual variability of landfast sea ice in Atka Bay, Weddell Sea, Antarctica

Seasonal and interannual variability of landfast sea ice in Atka Bay, Weddell Sea, Antarctica

Bathymetry Beneath Ice Shelves of Western Dronning Maud Land, East Antarctica, and Implications on Ice Shelf Stability

Characteristics of ice rises and ice rumples in Dronning Maud Land and Enderby Land, Antarctica

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