Researchers: Antarctica is losing ice

Melting is 3 times as fast as it was a decade ago

Between 60 percent and 90 percent of the world’s fresh water is frozen in the ice sheets of Antarctica, a continent roughly the size of the United States and Mexico combined. If all that ice melted, it would be enough to raise the world’s sea levels by roughly 200 feet.

While that won’t happen overnight, Antarctica is indeed melting, and a study published Wednesday in the journal Nature shows that the melting is speeding up.

The rate at which Antarctica is losing ice has tripled since 2007, according to the latest available data. The continent is now melting so fast, scientists say, that it will contribute 6 inches to sealevel rise by 2100. That is at the upper end of what the Intergovernmental Panel on Climate Change has estimated Antarctica alone could contribute to sea-level rise this century.

“Around Brooklyn you get flooding once a year or so, but if you raise sea level by [6 inches] then that’s going to happen 20 times a year,” said Andrew Shepherd, a professor of earth observation at the University of Leeds and the lead author of the study.

Even under ordinary conditions, Antarctica’s landscape is perpetually changing as icebergs calve, snow falls and ice melts on the surface, forming glacial sinkholes known as moulins. But what concerns scientists is the balance of how much snow and ice accumulates in a given year versus the amount that is lost.

Between 1992 and 2017, Antarctica shed 3 trillion tons of ice. This has led to an increase in sea levels of roughly three-tenths of an inch, which doesn’t seem like much. But 40 percent of that increase came from the last five years of the study period, from 2012-17.

Antarctica is not the only contributor to sea-level rise. Greenland lost an estimated 1 trillion tons of ice between 2011-14. And as oceans warm, their waters expand and occupy more space, also raising sea levels. The melting ice and warming waters have all been primarily driven by human emissions of greenhouse gases.

The study also helps clear up some uncertainty that was linked to regional differences in Antarctica. West Antarctica and the Antarctic Peninsula, which reaches toward South America, have been known for some time to be losing ice. In East Antarctica the picture has been muddled as the ice sheet there gained mass in some years and lost mass in others.

Advancements in Earth-observing satellites have enabled researchers to better understand the polar regions. Researchers once thought the polar regions would add ice as the climate warmed, because warmer temperatures lead to more moisture, which leads to more rain, and, they thought, more snow at the poles. Direct observation from satellites upended that view.

Researchers like Shepherd fear that future knowledge from satellites is at risk, however. Budgets proposed by the Trump administration have called for a reduction in some Earth-observation programs. “We depend upon the satellite measurements to not only tell us how the ice sheets respond but also to make these calculations to sea-level contribution,” Shepherd said.