Antarctic Ice Core Reveals Sheet Melt Intensified Ten-Fold: Climate Change Strikes Again

Most people were aware that the Antarctic sea ice was melting--they just didn't realize how fast. A new 1,000-year Antarctic Peninsula climate reconstruction reveals that summer ice melting has intensified ten-fold and that most of that melting has occurred in the mid-20^th century.

In order to make this climate reconstruction, researchers examined an ice core drilled in 2008 that was over 1,000 feet long. First collected from James Ross Island near the northern tip of the Antarctic Peninsula, the core was originally used to measure past temperatures in the area. Yet only recently have the scientists used it to examine ice melt in the region.

The core possesses layers that indicate periods of thawing and freezing. Like the rings of a tree, these layers reveal seasons and years, giving scientists an in-depth look at the past history of the area. The thickness of the layers also allowed them to examine how melting periods have changed over the past 1,000 years.

"We found that the coolest conditions on the Antarctic Peninsula and the lowest amount of summer melt occurred around 600 years ago," said Nerilie Abram, lead author, in a press release. "At that time, temperatures were around 1.6 degrees C lower than those recorded in the late 20^th Century, and the amount of annual snowfall that melted and refroze was about .5 percent. Today, we see almost ten times as much of the annual snowfall melting each year."

Currently, summer melting at the Antarctic site is at a level that is higher than at any other time over the past 1,000 years. While temperatures increase gradually in phases over many hundreds of years, most of the intensification of melting has happened since the mid-20^th century. In addition, the ice is at a point where even a small amount of warming can cause a massive amount of melt; it's at a tipping point which could spell an ice-free summer in coming years.

Yet do the findings really give evidence for global warming? A University of Washington professor and Earth and space sciences is skeptical. Eric Steig believes that the current melting trends aren't anything unusual--at least when looking on a shorter timescale.

"If we could look back at this region of Antarctica in the 1940s and 1830s, we would find that the regional climate would look a lot like it does today, and I think we would also find the glaciers retreating much as they are today," said Steig in a news release.

That's not to say that the melting isn't unprecedented on a larger timescale, though. What happens to the ice sheet in the coming decades will depend greatly on what happens throughout the rest of the world, but it is likely that more melting will occur.

The findings are published in the journal Nature Geoscience.