Antarctic Ice Sheet dynamics and contribution to sea level rise during the Last Interglacial

• Main Author: Millman, Helen
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UNSW, Sydney 2019
• Subjects: Ice sheets; Antarctica; Sea level; Glaciology; Ice sheet modelling; Palaeoclimate; Antarctic; The Antarctic; Greenland; Antarc*; ice core; Ice Sheet
• Online Access: http://hdl.handle.net/1959.4/66753; https://unsworks.unsw.edu.au/bitstreams/ce22832b-4497-4f37-a7df-6cb557fde81b/download; https://doi.org/10.26190/unsworks/21831

Sea levels have been rising since the early 20th century due to the increase in global temperatures predominantly caused by anthropogenic forcing. Although sea level rise is one of the major challenges we face today, the magnitude of future sea level rise remains uncertain due to a lack of understanding of dynamic feedbacks and tipping points in both the climate system and cryosphere. As proxy records and current observations are fragmentary and have limited spatial and temporal coverage, numerical modelling can help to explore these crucial areas. It is thought that projected global mean surface temperatures will be ∼1-4◦C above pre- industrial values by the end of this century, and whilst no past period truly reflects the potential future under anthropogenic climate change, past warm periods can be useful process analogues for future change. The Last Interglacial (LIG) was the last warm period before the present day, occurring 129-116k years ago. It is especially useful as a process analogue due to the relative abundance of proxy data from this time. Importantly, with amplified temperatures at high latitudes (polar amplification) global average temperatures during this period were up to 3◦C warmer than pre-industrial times. It is thought that global mean sea level (GMSL) during the LIG was 5 to 10 m higher than present. The Greenland Ice Sheet is believed to have contributed 0.6 to 4.3 m to LIG GMSL, and -0.2 to 0.4 m may be attributed to thermal expansion. With 60 m sea level equivalent (SLE) ice volume, the Antarctic Ice Sheets are the largest potential contributor to sea level rise, but they are also associated with the largest unknowns. Climate models consistently underestimate the level of warming during the LIG, and ice sheet modelling studies have been unable to reconstruct the apparent LIG sea level shown in the palaeo-records without significant changes to the model physics. LIG CO2 levels from ice core records show a variation of up to σ4, where σ represents standard deviation. It can take many years ...