Strong Geothermal Heating Under Ice Sheets Discovered

“When you add the effects of global warming, things can start to change quickly,” Fisher said.

This is the first ever geothermal heat flux measurements carried out underneath the West Antarctic ice sheet.

According to Andrew Fisher of UC Santa Cruz, lead author of the paper, the heating is not sufficient to account for the level of melting found in the West Antarctic.

The authors say reconstructing past ice sheet mass loss and forcings “will be of particular value for validation of coupled ice sheet-climate models” used to predict the future fate of polar ice sheets.

Heat flowing toward the base of the West Antarctic ice sheet is higher than expected.

Using a lengthy probe, researchers measured the flow of heat in the sediments below the ice sheet. Recent observations show accelerating retreat of some major outlet glaciers, especially in West Antarctica where the bed of the ice sheet lies hundreds of meters below sea level, hinting that a massive runaway ice-retreat may be already underway. It may help explain why there are lakes beneath the ice sheet and why parts of the ice sheet flow rapidly in what are described as ‘ice streams.’ These streams are thought to be responsible for carrying significant amounts of ice onto floating ice shelves located at the edges of the West Antarctic ice sheet.

“For the Antarctic ice sheet, the key challenge involves determining which marine-based sectors of the ice sheet are most vulnerable to collapse and identifying the forcing (atmospheric or oceanic) that would trigger such events”, DeConto and colleagues add. He clarifies that this applies to the parts of the ice sheet resting on bedrock below sea level.

The warmer than anticipated temperatures could also help to explain the diversity of microbial life found in subglacial lakes, as reported in the journal Nature previous year. “This is a region where there is volcanic activity, so this measurement may be due to a local heat source in the crust”, said Fisher.

Their study is part of an Antarctic drilling project that is being funded by the National Science Foundation under the WISSARD (Whillans Ice Stream Subglacial Access Research Drilling) program.

The finding could help to understand how the entire system, including global warming, is melting the ice.

The geothermal heating also explains the presence of sizable subglacial lakes that have been recently detailed by researchers. These findings have heightened concerns about the overall stability of the West Antarctic ice sheet.

Fisher and his team were able to measure the flow of heat at 285 milliwatts per square meter. The researchers also measured the upward heat flux through the ice sheet (about 105 milliwatts per square meter) using an instrument developed by coauthor Scott Tyler at the University of Nevada, Reno. This flow of water only increases that rate of ice loss, scientists believe. Fisher represents UC Santa Cruz as a professor of Earth and planetary sciences. So, according to Fisher, he and his team don’t have any idea about how localized these excessively hot geothermal conditions can be. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region.