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Marine δ¹⁸O data reveal astronomical forcing of the climate and cryosphere during the Miocene, when atmosphericPco₂was on par with emissions scenarios over the next century. This inspired hypotheses for how Milankovitch cycles, ice-ocean interactions, and greenhouse gases influence ice volume. Mass balance controls for marine and terrestrial ice sheets differ, and proxy data collected far from Antarctica provide valuable but limited insight into regional processes. We evaluate clast abundance data from Antarctic marine sedimentary records, observing a strong signal of eccentricity and precession coincident with a terrestrial ice sheet and a clear obliquity signal at the margins of a marine ice sheet. These analyses are integrated with a synthesis of proxy data, and we argue that high variance in obliquity forcing (mediated and enhanced by the ocean and atmosphere) can inhibit ice sheet growth, even when insolation forcing is conducive to glaciation. This “obliquity disruption” explains cryosphere variability before the existence of large northern hemisphere ice sheets. 

Abstract Antarctica’s continental margins pose an unknown submarine landslide-generated tsunami risk to Southern Hemisphere populations and infrastructure. Understanding the factors driving slope failure is essential to assessing future geohazards. Here, we present a multidisciplinary study of a major submarine landslide complex along the eastern Ross Sea continental slope (Antarctica) that identifies preconditioning factors and failure mechanisms. Weak layers, identified beneath three submarine landslides, consist of distinct packages of interbedded Miocene- to Pliocene-age diatom oozes and glaciomarine diamicts. The observed lithological differences, which arise from glacial to interglacial variations in biological productivity, ice proximity, and ocean circulation, caused changes in sediment deposition that inherently preconditioned slope failure. These recurrent Antarctic submarine landslides were likely triggered by seismicity associated with glacioisostatic readjustment, leading to failure within the preconditioned weak layers. Ongoing climate warming and ice retreat may increase regional glacioisostatic seismicity, triggering Antarctic submarine landslides. 

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).