Upper slope processes and seafloor ecosystems on the Sabrina continental slope, East Antarctica

Post, Alexandra L.; O’Brien, Philip E; Edwards, Stuart; Carroll, Andrew; Malakoff, K.; Armand, Leanne K.

doi:10.1016/j.margeo.2019.106091

Cited by 18 publications

(31 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, their long-profiles have negative slopes (i.e., deepen consistently down the flank of the highs) and their form is consistent with other Antarctic submarine gully systems (e.g. Gales et al, 2013;Post et al, 2019). Thus, we interpret the gullies as the result of the down-slope mass movement of material from the tops and sides of the H2 and H3 highs via gravitational processes into the small sediment fans at the base of the slope (Fig.…”

Section: Bathymetric Highs and Ridgessupporting

confidence: 81%

Revealing the former bed of Thwaites Glacier using sea-floor bathymetry

Hogan

Larter

Graham

et al. 2020

Preprint

View full text Add to dashboard Cite

Abstract. The geometry of the sea floor beyond Thwaites Glacier (TG) is a major control on the routing of warm ocean waters towards the ice stream’s grounding zone, which has led to increased mass loss through sub-ice-shelf melting and resulting accelerated ice flow. Nearshore topographic highs act as pinning points for the Thwaites Ice Shelf and potentially provide barriers to warm water incursions. To date, few vessels have been able to access this area due to persistent sea-ice and iceberg cover. This critical data gap was addressed in 2019 during the first cruise of the International Thwaites Glacier Collaboration (ITGC) project, with more than 2000 km2 of new multibeam echo-sounder data (MBES) were acquired offshore TG. Here, these data along with legacy MBES datasets are compiled to produce a set of standalone bathymetric grids for the inner Amundsen Sea shelf beyond both Pine Island and Thwaites glaciers. At TG, the bathymetry is dominated by a > 1200 m deep, structurally-controlled trough and discontinuous ridge, on which the Eastern Ice Shelf is pinned. The geometry and composition of the ridge varies spatially with some parts having distinctive flat-topped morphologies produced as their tops were planed-off by erosion at the base of the seaward-moving Thwaites Ice Shelf, suggesting a positive feedback mechanism for ice-shelf ungrounding. Knowing that this offshore area is a former bed for TG, we applied a novel spectral approach to investigate bed roughness and find that derived power spectra can be approximated using an inverse-square law, a result that is consistent with spectra for bed profiles from the modern TG. Using existing ice-flow theory, we also make a first assessment of the form drag (basal drag contribution) for ice flow over this topography. Ice flowing over the sea-floor troughs and ridges would have been affected by similarly high basal drag to that acting in the grounding zone today. We show that the sea-floor bathymetry is an analogue for extant bed areas of TG and that more can be gleaned from these 3D bathymetric datasets regarding the likely spatial variability of bed roughness and bed composition types underneath TG. Comparisons with existing regional bathymetric compilations for the area show that high-frequency (finer than 5 km) bathymetric variability beyond Antarctic ice shelves can only be resolved by observations such as MBES and that without these data calculations of the capacity of bathymetric troughs, and thus oceanic heat flux, may be significantly underestimated. This work meets the requirements of recent numerical ice-sheet and ocean modelling studies that have recognised the need for accurate and high-resolution bathymetry to determine warm water routing to the grounding zone and, ultimately, for predicting glacier retreat behaviour.

show abstract

Section: Bathymetric Highs and Ridgessupporting

confidence: 81%

Revealing the former bed of Thwaites Glacier using sea-floor bathymetry

Hogan

Larter

Graham

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Fig. S1f; Gales et al, 2013;Post et al, 2020). Thus, we interpret the gullies as the result of the downslope mass movement of material from the tops and sides of the H2 and H3 highs via gravitational processes into the small sediment fans at the base of the slope (Fig.…”

Section: Bathymetric Highs and Ridgesmentioning

confidence: 87%

“…At TG we note that, at least for the duration of the observational record (∼ 55 years), the fast-flowing part of the glacier, which feeds the TGT (Fig. 2), has continued to move over the H2 and H3 highs, periodically extending several tens of kilometres before calving (Ferrigno et al, 1993;Rabus et al, 2003;Mac-Gregor et al, 2012), whereas the ice rumple at the end of the EIS restricts flow over H1, with most ice flow being diverted around the rumple (Rignot et al, 2001). It is perhaps interesting to also consider that upwards of 50 m of relative sealevel fall due to glacio-isostatic uplift is thought to have occurred on the inner Amundsen Sea shelf during the Holocene (Whitehouse et al, 2012) and that the uplift of any pinning points would naturally counter ungrounding.…”

Section: Implications From Sea-floor Morphologymentioning

confidence: 89%

“…As a result, marine areas beyond this have been rendered inaccessible by remnants of the TGT as they have drifted north-northwest, including the very large B-10 and B-22A icebergs that remained grounded on the continental shelf for decades after they had calved before 1965 and in 2002, respectively ( Fig. 1) (Ferrigno et al, 1993;Rabus et al, 2003;MacGregor et al, 2012). In contrast, the EIS remains pinned on a sea-floor high that restricts its flow (Rignot et al, 2001;Tinto and Bell, 2011;Jordan et al, 2020) and induces shear between the EIS and TGT.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Revealing the former bed of Thwaites Glacier using sea-floor bathymetry: implications for warm-water routing and bed controls on ice flow and buttressing

et al. 2020

View full text Add to dashboard Cite

Abstract. The geometry of the sea floor immediately beyond Antarctica's marine-terminating glaciers is a fundamental control on warm-water routing, but it also describes former topographic pinning points that have been important for ice-shelf buttressing. Unfortunately, this information is often lacking due to the inaccessibility of these areas for survey, leading to modelled or interpolated bathymetries being used as boundary conditions in numerical modelling simulations. At Thwaites Glacier (TG) this critical data gap was addressed in 2019 during the first cruise of the International Thwaites Glacier Collaboration (ITGC) project. We present more than 2000 km2 of new multibeam echo-sounder (MBES) data acquired in exceptional sea-ice conditions immediately offshore TG, and we update existing bathymetric compilations. The cross-sectional areas of sea-floor troughs are under-predicted by up to 40 % or are not resolved at all where MBES data are missing, suggesting that calculations of trough capacity, and thus oceanic heat flux, may be significantly underestimated. Spatial variations in the morphology of topographic highs, known to be former pinning points for the floating ice shelf of TG, indicate differences in bed composition that are supported by landform evidence. We discuss links to ice dynamics for an overriding ice mass including a potential positive feedback mechanism where erosion of soft erodible highs may lead to ice-shelf ungrounding even with little or no ice thinning. Analyses of bed roughnesses and basal drag contributions show that the sea-floor bathymetry in front of TG is an analogue for extant bed areas. Ice flow over the sea-floor troughs and ridges would have been affected by similarly high basal drag to that acting at the grounding zone today. We conclude that more can certainly be gleaned from these 3D bathymetric datasets regarding the likely spatial variability of bed roughness and bed composition types underneath TG. This work also addresses the requirements of recent numerical ice-sheet and ocean modelling studies that have recognised the need for accurate and high-resolution bathymetry to determine warm-water routing to the grounding zone and, ultimately, for predicting glacier retreat behaviour.

show abstract

“…Previous studies on the continental shelf of the Sabrina Coast provide evidence for maximum expansion of the ice sheet to within 2–5 km of the shelf break during past glaciations (Fernandez et al., 2018; Post et al., 2020), but uncertainty remains around the exact position of the maximum grounding line extent. During the last glacial period, as the ice sheet expanded close to the edge of the present‐day continental shelf, the advancing ice remobilized sediments on the continental shelf and redeposited them on the continental slope (Post et al., 2020). As the ice sheet retreated, rising sea‐level and sea‐surface temperatures in the Southern Ocean promoted iceberg calving and meltwater production (Weber et al., 2014).…”

Section: Background: a Brief Glaciological And Geological History Of mentioning

confidence: 99%

Scratching the Surface: A Marine Sediment Provenance Record From the Continental Slope of Central Wilkes Land, East Antarctica

Tooze

Halpin

Noble

et al. 2020

Geochem Geophys Geosyst

Self Cite

View full text Add to dashboard Cite

The subglacial geology of Wilkes Land, East Antarctica, is poorly characterized, due to its concealment beneath 0.4-4 km of thick ice (Fretwell et al., 2013) with sparse coastal rock outcrop. Yet, a better understanding of the ice-covered continental crust has the potential to provide valuable insights into the dynamic tectonic history of East Antarctica and its role during supercontinent cycles (e.g., Aitken et al., 2016a;

show abstract

Upper slope processes and seafloor ecosystems on the Sabrina continental slope, East Antarctica

Cited by 18 publications

References 48 publications

Revealing the former bed of Thwaites Glacier using sea-floor bathymetry

Revealing the former bed of Thwaites Glacier using sea-floor bathymetry

Revealing the former bed of Thwaites Glacier using sea-floor bathymetry: implications for warm-water routing and bed controls on ice flow and buttressing

Scratching the Surface: A Marine Sediment Provenance Record From the Continental Slope of Central Wilkes Land, East Antarctica

Contact Info

Product

Resources

About