Understanding the controls on the extension and the timing of the Patagonian Ice Sheet during the last glacial cycle

Abstract

Patagonia is an interesting site to research the past climatic conditions upon glacier studies, because it hosts the larger ice body outside Antarctica in the Southern Hemisphere. This is important in the present and past context of regional climate and global sea level. Moreover, it is the only land of mass that straddles the core of the Southern Westerly Winds (SWWs), which are a critical climatic control in the higher latitudes of the Southern Hemisphere and are directly linked to the precipitations in the area. Several works focused on reconstructing the timings of past glaciations of the former Patagonian Ice Sheet (PIS). However, the geochronology shows an asynchrony in the timings of the ice maxima along the last glacial cycle. Reasons for this are still unclear, but most of them are centred around differences in the past configurations of the SWWs.

This thesis combines different approaches to tackle the asynchrony problem. It studies the glacial geomorphology and geochronology of the Seno Skyring ice lobe, which was previously under-studied. Additionally, through transient ice sheet modelling, it explores the climatic conditions required to simulate the growth and decay of the whole PIS through the last glacial cycle by constraining the model ice extent with geomorphological and chronological records (published and from this work).

The modelling suggests that the asynchrony along Patagonia is likely related to the interaction of climatic and topographic controls. Where the SWWs’ core expanded northwards with respect to today’s position, bringing wetter conditions towards central and northern Patagonia with an oscillating northern extent through the last glacial cycle. Moreover, topographic differences within the northern, central, and southern PIS are also crucial in the evolution of mass balance change and local ice glacier response, producing differences in the resilience of the deglaciation, thus more advantageous positions during a glacial readvance.