The ocean-driven instability of the South Pacific sector of the West
Antarctic Ice Sheet since 773 ka
Abstract
Insight into the causes of the West Antarctic Ice Sheet (WAIS) stability
over middle Pleistocene glacial/interglacial (G/IG) cycles is
fundamental to our understanding of the response of the climate system
to the cryosphere. Here, to clarify the mechanism of WAIS stability
during the late Quaternary period, we provide iceberg-rafted debris
(IRD) contents, clay mineral, and Sr-Nd isotopic analyses of the piston
core ANT34/A2-10. The core was recovered from the seasonal sea ice
region in the Antarctic Zone of the Amundsen Sea with a
~773 ka BP chronology. The endmember analysis of clay
minerals shows marked differences in sediment provenance at site
ANT34/A2-10 between IRD peak interval and low IRD content interval in
G/IG cycles. And the Sr-Nd isotopic endmember analysis in IRD peak
intervals restricts the sediment provenance in the Victoria Land. We
suggest that shifts in the sediment provenance resulted from the
variations in iceberg trajectories, which connected to the significant
shifts in the atmospheric system at the IRD peak intervals.
Moreover, a contemporaneous strengthened ocean-driven positive feedback
occurred between the increased wind-driven upwelling of warm,
well-ventilated Circumpolar Deep Water and the intense ice mass loss
process (including iceberg calving and basal melting process) with the
instability of the WAIS. Furthermore, our results reveal that the
variation of WAIS stability is sensitive to the local summer insolation
forcing. These pieces of evidence recorded in the pelagic South Pacific
Southern Ocean may strongly reflect the significant variations in
ocean-driven and orbital forcing on WAIS stability on the orbital scale.