West Antarctic Ice Sheet retreat during the Last Interglacial

The Last Interglacial (116 ka - 130 ka) is the most recent time when Earth's climate was as warm or warmer than it is today. It therefore may make a suitable proxy for understanding the impacts of modern climate change. One such impact of immediate relevance to the modern world is that of sea level rise. Global sea level is currently rising at an accelerating pace, threatening lives and economies around the world. Notably, evidence from paleoclimate data suggests global sea level during the Last Interglacial was at least 6.6 m higher than present sea level and perhaps more than 8 m higher. As the Earth adjusts to the rapid onset of modern climate change, we may expect sea level to approach that of the Last Interglacial.

Noticeable changes in sea level have a number of sources, including melting glaciers, ice sheets, and ocean thermal expansion. The Antarctic Ice Sheet has been inferred to be the largest contributor to Last Interglacial sea level change, adding between 4.1 and 5.8 m to global sea level during that time. Most of this change is expected to come from the West Antarctic Ice Sheet, which is thought to be prone to marine ice sheet instability. However, uncertain basal boundary conditions and ocean forcing make it a challenge to know how the ice sheet may have lost such a large amount of mass.

In this work, I seek to better constrain mass balance and sea level contributions of the Antarctic Ice Sheet during the Last Interglacial and explore evidence from inside the ice sheet itself which may reveal if and how the ice sheet sustained such a large mass balance change during the Last Interglacial. To do so, I use a transient ice sheet model to simulate reconfiguration of the Antarctic Ice Sheet under Last Interglacial conditions and find a stable configuration consistent with estimates of Antarctic contributions to Last Interglacial sea level. I then analyze englacial radar stratigraphy to study the ice dynamics by dating a series of isochronous englacial reflectors which have been mapped through the central West Antarctic Ice Sheet. For comparison to this data, I implement a steady state ice sheet model to simulate englacial isochronous surfaces with various uncertain model boundary conditions.