Warm oceans stop Antarctic ice from recovering

(Supplied / Knut Christianson)
(Supplied / Knut Christianson)

While warming atmospheres have been long linked to damaging melts in Antarctica, it hasn't previously been known how destructive warming oceans would be.

But new research led by Robert DeConto at the University of Massachusetts, US, suggests a warmer ocean could severely delay the ice's recovery.

They reconstructed the average sea level during two previous warming periods, the Pilocene (around 3 million years ago) and the Last Interglacial (130,000 to 115,000 years ago).

During the Last Interglacial period, carbon dioxide levels were considerably lower than they are today at 280 parts per million, compared to 400 parts per million and rising.

And during that period, global temperatures were around 0-2degC warmer than today.

But despite the similar temperatures and the considerably reduced carbon dioxide levels, the sea level was 6-9.3m higher than it is now.

It's likely it was because of the oceanic temperatures rather than the atmospheric, the study's authors suggest, saying "substantial oceanic warming" could have been the "determining factor" in the ice's retreat.

In the simulations, it was found that warmer waters around Antarctica could kickstart the collapse of an ice shelf.

While ice shelves are generally hundreds of metres thick, warm oceans running beneath them can wear them down quickly, destroying the stabilising structures holding them in place.

And there's precious little of the shelves we can afford to lose before risking cataclysmic damage.

"If protective ice shelves were suddenly lost … exposed grounding-line ice cliffs would quickly succumb to structure failure," the scientists say in the paper.

In another simulation examining the long-term effects of the climate change and potential ice loss, the scientists maintained a constant ocean level instead of continuing to raise it.

The simulation, which ran 5000 years into the future, found that even a consistently warmed ocean would inhibit ice from refreezing for thousands of years.

Even in a scenario with carbon dioxide levels reducing over time, the Antarctic ice sheet was unable to recover until the ocean cooled.

The research was published in the Springer Nature journal today.