Publication Date:
2018-08-10
Description:
Subglacial meltwater facilitates rapid ice flow beneath
concurrent ice sheets, and there is widespread evidence for a
dynamic subglacial water system beneath the Antarctic ice
sheet. It steers and affects the pattern of ice flow and is a
direct result from boundary processes acting at the base of
the ice sheet, i.e. pressure-induced basal melting.
Consequently, the occurrence of subglacial meltwater plays
an important role in bedrock erosion, subsequent resedimentation,
and in shaping the topography of ice-sheet
beds. Here we present new geological and geochemical data
from sediments recovered on the West Antarctic continental
shelf in Pine Island Bay that we interpret as reliable indicators
for deposition in a palaeo-subglacial lake beneath the
formerly expanded West Antarctic ice sheet, presumably
during or following the Last Glacial Maximum. Characteristic
changes of sedimentary facies and geochemical profiles
within these cores taken on RV Polarstern expeditions ANTXXIII/
4 (2006) and ANT-XXVI/3 (2010) support the presence
of an active subglacial lake system during the late stages of
the last glacial period. These findings have important
implications for palaeo ice-sheet dynamics, suggesting there
was considerable water available to lubricate the bedrock–ice
interface and deposit water-saturated subglacial sediments
(soft tills). Based on our investigations performed so far, we
suggest that the transition from subglacial lake to contact
with the ocean took place in the early Holocene. During this
time we speculate that the ice sheet thinned and successively
transformed into an ice shelf with sub-ice cavities flushed by
tidal currents. Based on bathymetric maps and relative sealevel
curves we will aim to estimate ice thickness as the
grounding line retreated across the subglacial lake threshold
further inland. Our findings may also have implications for
ice-sheet models, which have to consider the predominantly
non-linear effects related to subglacial hydrology.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Conference
,
notRev