How Antarctica melts mystery ‘solved’:
But how, exactly, the planet’s ice continent — far colder than the Arctic, and thus less subject to melting — disintegrated remained a mystery.
Building on earlier work, Professor DeConto and Pennsylvania State University climate scientist David Pollard created computer models integrating for the first time two mechanisms that appeared to solve the puzzle.
One is a process called hydrofracturing — if you put a sealed bottle of water or beer in a freezer, the liquid will expand and crack the container.
GIF: Antarctic warming
“That’s what happened here,” said Anders Levermann, an expert on the dynamics of ice sheets at the Potsdam Institute in Germany and a lead author of the chapter on sea levels in the most recent IPCC report.
“You have meltwater going deep into crevices in the ice sheet, and then it expands and cracks the ice open .”
Up to now, scientists have focused mostly on the impact warming oceans have on the overhang from ice sheets, which sit on land.
But it turns out air temperatures have risen enough to cause some melting on top as well.
The other natural mechanism is the breakup of buttressing ice shelves, and the failure of ice cliffs, that both act as dams for the ice sheets behind them.
“These are not ‘new’ processes per se,” Professor DeConto said.
“But they haven’t been considered at the continental scale in Antarctica before.”
When the researchers applied their models to the previous periods of warming, the pieces of the puzzle fell into place, he said.
It also gave rise to alarming conclusions about what lies ahead.
“The fact that a model — tested and calibrated against past examples of sea level rise — simulates such a strong future response to warming if very concerning,” he said.
“This should be a wake up call.”
The study adds to new evidence that ocean water marks may go up more and faster that previously thought, other scientists said.
“The recent modelling now favour the view that continuing rapid warming will cause sea level rise to be larger, and perhaps much larger, especially if we look beyond the end of this century,” Richard Alley, also a scientist at Pennsylvania State University, said.
Professor DeConto did note, however, that if humanity succeeds in drastically reducing greenhouse gas emissions in the coming decades, there is relatively little contribution to sea level rise from Antarctica.
“That’s the good news here,” he added.
