Ice Sheet Collapse, Sea Level Rise and Coastal Response

The response of polar ice sheets to modest increases in global temperature and the rate of future sea-level rise remains highly uncertain. One way of addressing these uncertainties is to examine past interglacials, which contain records of both changes in ice sheet mass balance and associated coastal response under a warm or slightly warmer climate system compared to present. However most of the geological record of Antarctic Ice Sheet extent during warmer interglacials has been lost due to glacial expansion and retreat cycles, An alternative and as yet untested approach for constraining ice sheet mass balance under warmer climates utilises the unique sea level fingerprint that results from a collapsing ice sheet. Principally the melting of individual ice sheets and glaciers over time scales of centuries to millennia drives perturbations in the Earth’s gravitational field, solid surface elevation and rotational state. Collectively, these effects contribute to significant geographic variation in eustatic sea level.

This talk I focuses on the last interglacial period spanning 128 to 116 ka. This period is characterised by global mean temperatures several degrees warmer than pre-industrial, and is therefore considered an analogue for near-future climate change. There is also a strengthening scientific consensus, and significantly from a near-future analogue perspective, that eustatic sea level peaked between 5 and 9 m above modern during the last interglacial, and was the result of the collapse of one or more of three significant Polar ice sheets, West Antarctic Ice Sheet, East Antarctic Ice Sheet or Greenland Ice Sheet. This finding carries significant implications for future polar ice sheet instability in the face of a relatively moderate global warming.

The overarching hypothesis is that LIG ice sheet melting history has left its discernable imprint of marine transgression along coastlines remote from the ice sheets and presents us with a unique opportunity to invert the problem.