A new study conducted by scientists from Rice University reveals that a 100,000-square-mile section of Antarctica's nation-sized Ross Ice Shelf broke apart within 1,500 years of a warming period that took place after the last ice age, providing clues to how the shelf may respond to the Earth's current warming climate. The Ross Ice Shelf is currently the world's largest ice shelf, although at the end of the last ice age it was much bigger, expanding much farther north and covering the entire Ross Sea.
"At the height of the last ice age, we know that the sheet of ice covering the Antarctic continent was larger and thicker than it is today," John Anderson, who participated in the research, said in a press release. "This continent-enveloping ice sheet extended all the way to the continental shelf, and in western Antarctica it filled the entire Ross Sea basin."
Analysis of the geologic record showed that as early as 18,000 years ago, the Ross basin was filled with ice that was so thick and heavy that it was stuck on the seafloor all the way to the edge of the continental shelf.
"We found that about 10,000 years ago, this thick, grounded ice sheet broke apart in dramatic fashion," Anderson said. "The evidence shows that an armada of icebergs - each at least twice as tall as the Empire State Building - was pushed out en masse. We know this because this part of the Ross Sea is about 550 meters (1,804 feet) deep, and the icebergs were so large and so tightly packed that they gouged huge furrows into the seafloor as they moved north."
The team of researchers measured these furrows using a seafloor mapping system over the course of a 56-day cruise in 2015 and noticed that other features formed by the retreating ice that were preserved on the seafloor showed a rapid retreat of the grounded ice after the initial collapse, a retreat that fell back hundreds of miles in a stair-step fashion.
The knowledge gained from this study can help us use past ice sheet and ice shelf behavior to predict how current ice sheets and ice shelves may respond to climate change and future warming. In particular, rates of response to atmospheric and oceanic warming are key indicators.
"There are similarities to what we see the modern Ross Ice Shelf doing," Anderson said. "The farthest boundary of the ice shelf extends nearly 1,000 kilometers (621 miles) from the grounding line, where the ice sheet is grounded in about 800 meters (2,625 feet) of water. That's a condition that most glaciologists consider unstable, and it is not unlike the situation that existed prior to the big breakup that began 5,000 years ago."
The findings were published in the Jan. 15 issue of the Proceedings of the National Academy of Sciences.
