Melting of Antarctica's Wilkes Basin may cause 4m sea-level rise, akin to ice loss 400,000 years ago: Study

A rise in sea level could threaten to submerge coastlines and some cities. The study opens the possibility that sea level may rise more than previously thought


                            Melting of Antarctica's Wilkes Basin may cause 4m sea-level rise, akin to ice loss 400,000 years ago: Study
(Terry Blackburn)

About 400,000 years ago, Eastern Antarctica's Wilkes Basin lost enough ice to cause a sea-level rise of about three to four meters, a new study suggests. The period saw temperatures that were only one to two degrees celsius warmer than today, raising questions on what it could mean for our planet's near future.

For decades, Western Antarctica has received global attention. It sits on land below sea-level, making it vulnerable to ice sheet melting. Scientists predicted that the ice loss could contribute to a sea-level rise of 3 to 4 meters, threatening to submerge coastlines, including some cities across the world.

But parts of Eastern Antarctica, including the Wilkes Basin, which also rests on land below sea level, has mostly remained in the shadows of its western counterpart. "The East Antarctic ice sheet, which is much larger, has been considered to be relatively stable," Dr Slawek Tulaczyk, a professor of Earth and planetary sciences at UC Santa Cruz, and co-author of the study, told MEA WorldWide (MEAWW). Until recently, scientists thought the region has been stable for the last 5-15 million years and is not in danger, he added.

More recently, scientists began thinking that the Wilkes Basin and other eastern parts of the continent may become unstable if temperatures turn slightly warmer than the current times. "Our study opens the possibility that sea level may rise more than previously thought as the global climate will warm," Tulaczyk explained.

To arrive at these findings, the team turned to rocks lying beneath the Wilkes Basin's ice sheet. These samples contain evidence of ice loss from the basin about 400,000 years ago. By estimating the age and studying the mineral composition, the team observed that the ice sheet in the region retreated 700 kilometers during that period. "That probably contributed 3 to 4 meters to global sea-level rise, with Greenland and West Antarctica together contributing another 10 meters," Blackburn explained.

By studying mineral deposits in these rocks, scientists noted that the ice sheet in the region retreated 700 kilometers during that period (Michael Scudder)

Though the temperatures about 400,000 years ago are comparable to modern times, it is unlikely that Wilkes ice sheet melting will happen anytime soon. It will take time for that much ice to melt, according to researchers.

So, when is it likely to happen? Scientists are unsure because there are no reliable models to make such forecasts. But geologic records of the sea level rise during the end of the last Ice Age, when temperatures increased by 5 degrees Celsius, may offer some clues. "When ice sheets became unstable due to this warming, they caused sea-level rise at the rate of up to 4-6 cm per year (ca. 15,000 years ago). I think that this is a reasonable 'maximum speed limit' that we can assume for future sea-level rise. At these rates, 3-4 meters of sea-level rise could happen within 50 to 100 years, "Tulaczyk said. 

However, the study has a few limitations. The team studied a few portions on the eastern side of the Wilkes Basin. As a result, Tulaczyk and his team do not have the full picture of how far the ice sheet retreated 400,000 years ago. He added that the loss might have been more, but they do not have enough samples to investigate it.

"Nonetheless, our results open the possibility that the ice sheet moving over other basins similar to the Wilkes basin also experienced retreat during that period. These parts also may become vulnerable to retreat under future warmer climates," Tulaczyk added.

The study is published in Nature.

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