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Abstract In the southern Indian Ocean, the position of the subtropical front – the boundary between colder, fresher waters to the south and warmer, saltier waters to the north – has a strong influence on the upper ocean hydrodynamics and biogeochemistry. Here we analyse a sedimentary record from the Agulhas Plateau, located close to the modern position of the subtropical front and use alkenones and coccolith assemblages to reconstruct oceanographic conditions over the past 300,000 years. We identify a strong glacial-interglacial variability in sea surface temperature and productivity associated with subtropical front migration over the Agulhas Plateau, as well as shorter-term high frequency variability aligned with variations in high latitude insolation. Alkenone and coccolith abundances, in combination with diatom and organic carbon records indicate high glacial export productivity. We conclude that the biological pump was more efficient and strengthened during glacial periods, which could partly account for the reported reduction in atmospheric carbon dioxide concentrations. 

Abstract. The West Antarctic Ice Sheet (WAIS) presently holds enough ice to raise global sea level by 4.3 m if completely melted. The unknownresponse of the WAIS to future warming remains a significant challenge fornumerical models in quantifying predictions of future sea level rise. Sealevel rise is one of the clearest planet-wide signals of human-inducedclimate change. The Sensitivity of the West Antarctic Ice Sheet to a Warmingof 2 ∘C (SWAIS 2C) Project aims to understand past and currentdrivers and thresholds of WAIS dynamics to improve projections of the rateand size of ice sheet changes under a range of elevated greenhouse gaslevels in the atmosphere as well as the associated average globaltemperature scenarios to and beyond the +2 ∘C target of theParis Climate Agreement. Despite efforts through previous land and ship-based drilling on and alongthe Antarctic margin, unequivocal evidence of major WAIS retreat or collapse and its causes has remained elusive. To evaluate and plan for theinterdisciplinary scientific opportunities and engineering challenges thatan International Continental Drilling Program (ICDP) project along the Siple coast near the grounding zone of the WAIS could offer (Fig. 1), researchers, engineers, and logistics providers representing 10 countries held a virtualworkshop in October 2020. This international partnership comprised ofgeologists, glaciologists, oceanographers, geophysicists, microbiologists,climate and ice sheet modelers, and engineers outlined specific researchobjectives and logistical challenges associated with the recovery of Neogene and Quaternary geological records from the West Antarctic interior adjacent to the Kamb Ice Stream and at Crary Ice Rise. New geophysical surveys at these locations have identified drilling targets in which new drilling technologies will allow for the recovery of up to 200 m of sediments beneaththe ice sheet. Sub-ice-shelf records have so far proven difficult to obtainbut are critical to better constrain marine ice sheet sensitivity to pastand future increases in global mean surface temperature up to 2 ∘Cabove pre-industrial levels. Thus, the scientific and technological advances developed through this program will enable us to test whether WAIS collapsed during past intervals of warmth and determine its sensitivity to a +2 ∘C global warming threshold (UNFCCC, 2015).