Arctic melt

Source: By The Indian Express

The shrinkage of summer sea ice in the Arctic has long been a concern, as has been the survival of the species that depend on it for survival. A new study has now put a timeline to an impending disaster: If carbon emissions continue at current levels, summer ice will disappear by 2100 — and, along with it, creatures such as seals and polar bears. The study has been published in the journal Earth’s Future.

Ice and life

In winter, most of the Arctic Ocean surface freezes and scientists expect this to continue for the foreseeable future, even as the climate warms. In summer, when some of the ice melts, winds and currents carry it for great distances — some of it into the North Atlantic, but much of it into the Arctic’s farthest-north coasts, along Greenland and the Canadian islands.

This results in a rich marine ecosystem. On the Arctic ice, algae bloom. These feed tiny animals, which in turn feed fish, which in turn feed seals, which feed 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.

But with a warming climate, summer sea ice has been shrinking fast, and now consistently spans less than half the area it did in the early 1980s.

The findings

The study covers a 1 million-sq km region north of Greenland and the coasts of the Canadian Archipelago, where sea ice has traditionally been thickest round the year, and thus likely to be most resilient.

The researchers looked at two scenarios: optimistic (if carbon emissions are brought in check) and pessimistic (if emissions continue as they are). By 2050, summer ice in this region will dramatically thin. Under the optimistic scenario, some summer ice could persist indefinitely. Under the pessimistic scenario, summer ice would disappear by the end of the century.

Under the low-emissions scenario, ice from even the central Arctic will wane by mid-century, and will no longer endure through the year. Locally formed summer ice will persist in what is known as the Last Ice Area, but will now be only a metre thick.

The implications

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 western Alaska and parts of Hudson Bay.

However, under the higher-emissions scenario, by 2100, even the locally formed ice will disappear in summer, the study has found. With no summer ice anywhere, there will be no ice-dependent ecosystems.

“Unfortunately, this is a massive experiment we’re doing,” the Columbia University’s Climate School quotes a senior research scientist Robert Newton, co-author of the study, as saying. “If the year-round ice goes away, entire ice-dependent ecosystems will collapse, and something new will begin,” he is quoted as saying on the School’s website.

This may not mean the end of all life. “New things will emerge, but it may take some time for new creatures to invade.” Fish, algae etc may come up from the North Atlantic, but it is not clear if they could survive there year round. “…it may be getting warmer, but the planet’s rotation around the sun will not change, and any new occupants including photosynthetic organisms would have to deal with the long, sunless Arctic winter,” the statement said.