Paleo ice flow and subglacial meltwater dynamics in Pine Island Bay, West Antarctica

Abstract

Increasing evidence for an elaborate subglacial drainage network underneath modern Antarctic ice sheets suggests that basal meltwater has an important influence on ice stream flow. Swath bathymetry surveys from previously glaciated continental margins display morphological features indicative of subglacial meltwater flow in inner shelf areas of some paleo ice stream troughs. Over the last few years several expeditions to the Eastern Amundsen Sea embayment (West Antarctica) have investigated the paleo ice streams that extended from the Pine Island and Thwaites glaciers. A compilation of high-resolution swath bathymetry data from inner Pine Island Bay reveals details of a rough seabed topography including several deep channels that connect a series of basins. This complex basin and channel network is indicative of meltwater flow beneath the paleo-Pine Island and Thwaites ice streams, along with substantial subglacial water inflow from the east. This meltwater could have enhanced ice flow over the rough bedrock topography. Meltwater features diminish with the onset of linear features north of the basins. Similar features have previously been observed in several other areas, including the Dotson-Getz Trough (Western Amundsen Sea embayment) and Marguerite Bay (SW Antarctic Peninsula), suggesting that these features may be widespread around the Antarctic margin and that subglacial meltwater drainage played a major role in past ice-sheet dynamics

Evidence for a water system transition beneath Thwaites Glacier, West Antarctica

“…The system consists of a distributed network of canals ponding behind a bedrock ridge and feeding a system of concentrated channels downstream. Although the concentrated portion of the water system could occupy deeply incised channels like those observed on the deglaciated inner shelf (23), we do not observe deep water-filled basins, which are hypothesized as sources of meltwater floods capable of eroding those channels (23,24). The transition from a distributed to a concentrated water system occurs with increasing surface slope, water flux, and basal shear stress, providing observational evidence for the theorized control of the ice surface on the configuration of subglacial water as well as the control of the subglacial water on ice flow.…”

Palaeo-ice stream pathways and retreat style in the easternmost Amundsen Sea Embayment, West Antarctica, revealed by combined multibeam bathymetric and seismic data

“…1). Current LGM model simulations capture the locations and widths of palaeo-ice streams on the inner and middle shelf as mapped from bedforms (e.g., Larter et al, 2009;Nitsche et al, 2013), but considerable data-model mismatches remain on the outer shelf (Golledge et al, 2013(Golledge et al, , 2014. On the outer shelf of the eastern Amundsen Sea Embayment (ASE) in particular, model results reconstructing the widths of fast-flowing corridors deviate significantly from existing data constraints.…”

“…Several studies have investigated the post-LGM retreat pattern of the WAIS within the main PIT (e.g., Lowe and Anderson, 2002;Evans et al, 2006b;Graham et al, 2010;Jakobsson et al, 2012;Nitsche et al, 2013) and on an adjacent inter-ice stream area . Both the fast-and slow-flowing parts of the ice sheet in the eastern ASE retreated stepwise, as recorded by five GZWs within PIT and recessional moraines on the inter-ice stream ridge.…”

Glacial retreat in the Amundsen Sea sector, West Antarctica – first cosmogenic evidence from central Pine Island Bay and the Kohler Range

“…In addition, the influence on the ice-sheet dynamics of underlying tectonic structures, seen in bathymetry images (e.g. Nitsche et al, 2013) and geophysical mapping (e.g. Gohl et al, 2013aGohl et al, , 2013b, is still not fully understood.…”