DNA Explainer: Why the Arctic may not have any polar bears left by 2100

The pace with which climate change is affecting Earth, it is not far when the summer sea ice in the Arctic will disappear and along with it, creatures such as seals and polar bears will become extinct. A new study has revealed how a disaster is waiting to happen.

The study published in the journal Earth's Future says that if carbon emissions continue at current levels, summer ice will disappear by 2100. Due to climate warming summer sea ice has been shrinking fast, and now consistently spans less than half the area it did in the early 1980s. This summer sea ice has always helped in a rich marine ecosystem. Here we try to understand how?

How summer sea ice affects marine ecosystem

During winters most of the Arctic Ocean surface freezes and this continues even as the climate warms.

During the summer season when some of the ice melts, winds and currents carry it for great distances.

Some of it is carried into the North Atlantic, but much of it into the Arctic's farthest-north coasts.

This is mostly along Greenland and the Canadian islands. This results in a rich marine ecosystem. 

Algae grow on the Arctic ice which feeds tiny animals, this, in turn, feeds fish, which again, in turn, feeds seals.

This then feeds polar bears at the top of the chain.

The irregular topography also helps create lairs for seals, and ice caves for polar bears during the winter.

What the study says

The study covers one million-sq km region north of Greenland and the coasts of the Canadian Archipelago.

Here the sea ice has traditionally been thickest round the year, and thus likely to be most resilient.

The researchers looked at two scenarios -  if carbon emissions are brought in check and if emissions continue.

Under the optimistic scenario, if carbon emissions are brought in check some summer ice could persist indefinitely.

Under the pessimistic scenario, if emissions continue summer ice would disappear by the end of the century.

Under the low-emissions scenario, ice from even the central Arctic will wane by 2050 and will no longer endure through the year.

Locally formed summer ice will persist in what is known as the Last Ice Area and its thickness will reduce to a metre.

Impact of climate change on Arctic region

The study forecasts that under the low-emissions scenario, at least some seals, bears and other creatures may survive.

These species currently exist under similar summer conditions along with western Alaska and parts of Hudson Bay.

Under the higher-emissions scenario, by 2100, even the locally formed ice will disappear in summer, the study found.

With no summer ice anywhere, there will be no ice-dependent ecosystems and seals, bears and other creatures will be extinct.

(With Inputs from Earth's Future Journal)