Cyclic ice sheet collapses, meltwater events and proxies for a reduction of bottom water circulation along the West Antarctic Peninsula margin

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The melting of continental ice sheets during deglaciations provides freshwater to the oceans that affect the global sea level and the strength of the thermohaline circulation (THC). This is well documented in the Northern Hemisphere but less understood for the Southern Ocean. Recent climate models indicate that sea ice reduction, meltwater and deepwater formation in Antarctica is equally important for the meridional overturning circulation. Cores from drifts along the West Antarctic Peninsula offer the chance to study more than eighty deglaciation cycles with ice sheet collapses. During those collapses intriguing occurrences of iron diagenesis in conjunction with well-preserved diatom plume deposits suggest episodes of anaerobic sediment conditions and reduced bottom water dynamics. We propose to use U/Th as additional evidence for the suggested anoxic conditions. 34S-isotopes and diffusion reaction models will constrain the duration and vertical extend of anaerobic episodes in the sediment column. Those episodes documented from Sites of active Antarctic bottom water formation likely represent the peak in meltwater production and at the same time the onset of increased THC, initiating a gradual Antarctic cooling that preludes the next glaciation. Better constrains on Antarctic bottom water circulation will ultimately improve our understanding of South-North climate feedbacks.