By Juanita Constible, Science and Solutions Director

Image by Cloudzilla

Massive ice sheets, remnants of the most recent ice age, are found only in Greenland and Antarctica. With the ice sheets so far away, should the rest of us be concerned? Absolutely. As the world warms, many scientists are nervously watching those ice sheets shrink — and trying to figure out how much global sea levels could rise as a consequence.

A recent study in Nature Geoscience suggests that ocean warming will play a significant role in ice loss, “heighten[ing] the risk of future large sea-level rise.”

The rate of ice loss in Greenland and some parts of Antarctica has increased over the last decade or two. Increasing air temperatures are partially to blame. But as Jianjun Yin and his colleagues report in the new study, the bigger culprit is increasing ocean temperatures — specifically 200-500 meters under the surface.

The Antarctic and Greenland ice sheets are constantly flowing toward the sea under their own weight, a bit like lopsided scoops of ice cream oozing over the sides of their sugar cones. Normally, the flow of ice is moderated when individual glaciers or ice streams within an ice sheet get jammed against the bottom of the ocean or a floating ice shelf. But now, subsurface ocean water is acting like a “warm bath,” speeding ice melt and the flow of the ice sheet. And there’s more to come. The team found that a middle-of-the-road increase in carbon pollution could warm the subsurface waters around Greenland up to 2*C by the end of the century (nearly two times faster than the global average), and warm Antarctic waters by about 0.6*C over the same period.

Don’t breathe a sigh of relief just yet over the slower rate of warming in Antarctica. When you’re talking about an ice sheet containing 30 million cubic kilometers of ice, any shrinkage is worrisome. Take for example, the 40-km long Pine Island Glacier ice shelf, an extension of the West Antarctic ice sheet. Another recent study in Nature Geoscience reports that the amount of meltwater from the ice shelf has increased about 50% since 1994, due to a combination of warming and changes in ocean currents. An underwater cavity appears to be opening up under the shelf, allowing a larger volume of warm water to eat away at the bottom of the ice.

Together, these studies are a powerful reminder that we need to reduce carbon pollution and prepare for the effects of climate change that are happening now. That’s a message that leaders from coastal regions around the world already get. In California, for example, developers are being told to factor sea level rise into their building projects. And in Australia, the government is working to better communicate the risks of sea level rise to cities and rural areas through a website called OzCoasts.

Do you live on the coast? Leave a comment about what your community is doing — or should be doing — to prepare for sea level rise.