Publication Date:
2018-08-10
Description:
Multibeam swath bathymetry datasets collected over the past two decades have been compiled to identify palaeoice
stream pathways in the easternmost Amundsen Sea Embayment. We mapped 3010 glacial landforms to reconstruct
palaeo-ice flow in the �250 km-long Abbot Glacial Trough that was occupied by a large palaeo-ice
stream, fed by two tributaries (Cosgrove and Abbot) that reached the continental shelf edge during the last maximum
ice-sheet advance. The mapping has enabled a clear differentiation between glacial landforms interpreted
as indicative of wet- (e.g. mega-scale glacial lineations) and cold-based ice (e.g. hill-hole pairs) during the last
glaciation of the continental shelf. Both the regions of fast palaeo-ice flow within the palaeo-ice stream troughs,
and the regions of slow palaeo-ice flow on adjacent seafloor highs (referred to as inter-ice stream ridges) additionally
record glacial landforms such as grounding-zone wedges and recessional moraines that indicate grounding
line stillstands of the ice sheet during the last deglaciation from the shelf. As the palaeo-ice stream flowed along
a trough with variable geometry and variable subglacial substrate, it appears that trough sections characterized by
constrictions and outcropping hard substrate that changes the bed gradient, led the pace of grounding-line retreat to
slow and subsequently pause, resulting in the deposition of grounding-zone wedges. The stepped retreat recorded
within the Abbot Glacial Trough corresponds well to post-glacial stepped retreat interpreted for the neighbouring
Pine Island-Thwaites Palaeo-Ice Stream trough, thus suggesting a uniform pattern of episodic retreat across the
eastern Amundsen Sea Embayment. The correlation of episodic retreat features with geological boundaries further
emphasises the significance of subglacial geology in steering ice stream flow. Our new geomorphological map
of the easternmost Amundsen Sea Embayment resolves the pathways of palaeo-ice streams that were probably
all active during the last maximum extent of the ice sheet on this part of the shelf, and reveals the style of postglacial
grounding-line retreat. Both are important input variables in ice sheet models and therefore can be used for
validating the reliability of these models.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Conference
,
notRev
Format:
application/pdf
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