More Snow Over Antarctica Will Not Offset Rising Ocean Levels

May 23, 2016 | Joanne Kennell

Photo credit: NASA Goddard Space Flight Center/flickr (CC by SA 2.0)

During abrupt climate changes, there’s no relationship between snowfall and temperature.

There are many processes related to a warming climate that will work together to raise the planet’s ocean levels over the coming decades — these include melting snow and ice, the collapse of ice sheets, and the thermal expansion of the oceans.

One of the “brakes” to rising sea levels was supposed to be heavier snowfall over the continent of Antarctica. According to present climate model projections, since warmer air holds more moisture, more snow could be generated to slightly rebuild the glacier, offsetting some sea-level rise.

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However, a University of Washington (UW) study published in the journal Geophysical Research Letters, says: not so fast. The researchers used evidence from a West Antarctic Ice Sheet Divide ice core to understand how the continent’s snowfall has varied over the past 31,000 years.

"It's allowed us to look at the snow accumulation back in time in much more detail than we've been able to do with any other deep ice core in Antarctica," lead author T.J. Fudge, a UW postdoctoral researcher in Earth and space sciences, said in a UW news release. "We show that warmer temperatures and snowfall sometimes go together, but often they don't."

For example, 8,000 years ago when Earth was emerging from its last , the air temperature went up by several degrees without any increase in the amount of snowfall.

"Our results make it clear that we cannot have confidence in projections of future snowfall over Antarctica under global warming," said co-author Eric Steig, a UW professor of Earth and space sciences, in the release.

Many climate models predict that warming temperatures will result in more snow over Antarctica, and that because more snow is falling inland, it will counteract the mass lost to melting or calving at the continent’s edges. This extra snowfall could reverse 2 to 4 centimeters, or about 1 inch, of global sea-level rise by 2100, the researchers said.

"It's not a huge component," Fudge said, "but if you live close to sea level, centimeters certainly matter."

But temperature is an unreliable predictor of Antarctic snowfall because it depends on what part of the record is observed. In fact, during abrupt climate changes, there’s no relationship between snowfall and temperature, explained the authors.

This large variation in the historical record likely reflects shifts in atmospheric circulation patterns — particularly the winds. New research suggests winds play a big role in Antarctic temperature, sea ice, and weather, especially on shorter timescales.

"For sea-level rise, we're not really interested in what happens over thousands of years," Fudge said. "We're interested in what happens over the next few hundred years. At that shorter timescale, the variability in how the storms reach the continent matters much more than a few degrees of warming."

Patterns in the Antarctic are ultimately connected to weather patterns in the tropics. The snowfall record can help to understand how winds affect Antarctic weather, and how they influence the amount of warm, tropical ocean water that hits the frozen continent — and ultimately the impact on sea-level rise.

The study was funded by the National Science Foundation and NASA.

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