Asked by Mike
This is a very difficult question to answer. The West Antarctic Ice Sheet has a global eustatic sea level contribution of 3.2 m – that is, if all the ice in this area melted, global sea level would rise by 3.2 m. The Antarctic Peninsula Ice Sheet would contribute 0.24 m to global sea level rise on full melting, and currently contributes 0.22±0.16 mm per annum. The East Antarctic Ice Sheet has a sea level equivalent of approximately 60 m.
Global sea levels are predicted to rise by 20-60 mm by 2100, and possibly up to 1 metre. This is mostly from glacier melt and thermal expansion of the oceans. It does not include inputs from dynamic changes to ice sheet flow. The West Antarctic Ice Sheet rests on ground below sea level (see Marine Ice Sheet Instability Hypothesis), which makes it potentially unstable. It is possible that this could collapse rapidly and raise sea levels by 3.2 m, possibly within 500 years. Sea level increase of this rate and magnitude have been noted previously in the palaeo record. The West Antarctic Ice Sheet has probably collapsed in the past, when temperatures were comparable with today’s or temperatures projected in the next few centuries.
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