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.


Nature Geoscience – July 2015