Epic Antarctic ice sheet melt speeding up sea level rise

Mindy Sparks
Июня 14, 2018

"According to our analysis, there has been a step increase in ice losses from Antarctica during the past decade, and the continent is causing sea levels to rise faster today than at any time in the past 25 years", Shepherd said.

The measurements are vital information for the almost eight billion of us who don't live on Antarctica, because they allow scientists to compute sea level rise rates and contributions.

Already floating, ice shelves breaking off into icebergs do not add to sea level. They concluded that some ice on the southernmost part of the continent could be stable in a warming climate, as was the case during the Pliocene Epoch. However, the losses in the last five years have tripled over what they were in the first five years of the period. Their results - known formally as the "Ice Sheet Mass Balance Inter-comparison Exercise" (IMBIE) - were published Wednesday in the journal Nature. NSF funded the US participation in ANDRILL. The Antarctic Peninsula - the portion of the continent that reaches out for the southern tip of South America - has seen an increase from an average of 7 billion tonnes per year, up to 33 billion tonnes per year in that same time period.

The geological history of the massive ice sheet - frozen both above and, in many places, below the ocean's surface - has been hard to pinpoint.

Antarctica is not the only contributor to sea-level rise.

This study focused on the portion of the ice sheet that sits above the ocean.

Shepherd said Antarctica alone is now on track to raise world sea levels by about 12 inches by 2100, above most past estimates. "When we look into the ocean we find that it's too warm and the ice sheet can't withstand the temperatures that are surrounding it in the sea", he says.

"With the number of scientific studies focusing on this region, the technological tools we have at our disposal and data sets spanning several decades, we have an unequivocal picture of what's happening in Antarctica", Eric Rignot, an Earth system science professor at the University of California Irvine who participated in the research, said in a statement.

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NOAARapidly rising sea levels that inundate the coastlines where billions of people live is one of the more worrisome concerns associated with climate change. "We're saying that the terrestrial segment of the ice sheet is more resilient at current carbon-dioxide levels".

Shakun's co-authors on the paper include Carling C. Hay, also of Boston College; researchers Lee B. Corbett, Paul R. Bierman, Kristen Underwood and Donna M. Rizzo of the University of Vermont; Susan R. Zimmerman of the Lawrence Livermore National Laboratory; Marc W. Caffee of Purdue University; and Tim Naish and Nicholas R. Golledge of Victoria University of Wellington, New Zealand.

"[The Antarctic ice sheet] lost 2,720 billion tonnes [2.998 tons] of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 millimeters", the report said.

By century's end, sea level - compared to a pre-industrial benchmark - could increase from a few dozen centimetres to a metre or more, depending in part on efforts to curb greenhouse gas emissions.

As shown in the video above, these changes are not uniform over the entire Antarctic ice sheet.

The researchers analyzed sediment contained in drill cores taken from the sea floor. Researchers usually examine rock samples from hillsides, mountain tops and rivers to determine where and when ice retreated during prior geological eras.

In a new study, the most comprehensive to date of the continent's icy status, an global group of 84 researchers analyzed data from multiple satellite surveys, from 1992 to 2017. The findings helped confirm that the Greenland Ice Sheet is a sensitive responder to global climate change.

West Antarctica is now bearing the brunt of this loss, as its glacial ice shelves have been melted from below by warming deep ocean water. The Antarctic Peninsula is also shedding ice, though at a less rapid clip, while East Antarctica has remained fairly steady.

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