Warm water expands. The rate of sea level rise depends upon both how quickly the oceans warm and how fast polar ice melts. Recent historical research of the Greenland ice sheet discovered that melting has as much to do with how sustained warming is as how quickly it warms.
The Greenland ice sheet study found that sustained temperatures just above freezing were sufficient to melt glacial ice. “The duration of warmth above a given threshold is a critical determinant, underlining the role of ocean warming, as its inertia prolongs warmth and triggers longer-term feedbacks,” reported Norwegian Earth scientist Nil Irvali and colleagues.
Greenland is exemplary of polar ice sheets. Researchers earlier this year were surprised to discover that Antarctic glacial ice was melting underneath much faster than models forecast; much of that owing to only slightly warmer ocean waters around the ice.
Climate models have not incorporated this new finding, and hence underestimate glacial melt and sea level ascension. The prognosis is faster melting of the polar caps and attendant sea level rise.
References:
Ishi Nobu, The Fruits of Civilization, BookBaby (2019).
Nil Irvali et al, “A low climate threshold for south Greenland Ice Sheet demise during the Late Pleistocene,” PNAS (23 December 2019).
Bob Bermwyn, “Greenland’s nearing a climate tipping point. How long warming lasts will decide its fate, study says,” Inside Climate News (23 December 2019).
“Research reveals past rapid Antarctic ice loss due to ocean warming,” Phys.org (6 December 2019).
Chris Mooney, “Antarctic ice loss has tripled in a decade. If that continues, we are in serious trouble.,” The Washington Post (13 June 2018).