Accumulation and Marine Forcing of Ice Dynamics in the Western Ross Sea during the Last Deglaciation – Nature Geoscience – Hall/Denton et al.
The grounding line of the ice sheet in the Ross Sea, Antarctica,
retreated between the Last Glacial Maximum and the present.
However, the timing of the retreat and the interplay of factors
controlling ice stability in this region1 remain uncertain. Here
we use 180 radiocarbon dates to reconstruct the chronology
of moraine construction on the headlands adjacent to western
McMurdo Sound. On the basis of these dates we then assess
the timing of ice expansion and retreat in the Ross drainage
system that is fed from both the East and West Antarctic
ice sheets. We find that grounded ice in the western Ross
Sea achieved its greatest thickness and extent during the last
termination, between 12,800 and 18,700 years ago. Maximum
ice thickness at our site coincides with a period of high
accumulation as recorded by the West Antarctic Ice Sheet
Divide ice core2. Recession of the ice sheet from the headland
moraines began about 12,800 years ago, despite continued
high accumulation and the expansion of land-based glaciers at
this time. We therefore suggest that the grounding-line retreat
reflects an increased marine influence as sea levels rose and
the ocean warmed.We suggest that future instability in the ice
sheet grounding line 05 occur whenever the ocean forcing is
stronger than forcing from accumulation.