Researchers from UC Santa Cruz lowered a probe more than a half mile below the ice into the sediments below Subglacial Lake Whillans. What they found surprised them.
Heat flowing toward the base of the West Antarctic ice sheet is higher than expected. The heat in question is coming from geothermal sources deep inside the Earth.
Andrew Fisher, professor of Earth and planetary sciences at UC Santa Cruz was quick to point out this geothermal heating doesn’t directly explain the ice loss seen in the West Antarctic ice sheet recently.
“The ice sheet developed and evolved with the geothermal heat flux coming up from below–it’s part of the system. But this could help explain why the ice sheet is so unstable. When you add the effects of global warming, things can start to change quickly,” Fisher said.
What does the heat flow mean? It could help explain why there are lakes below 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.
Fisher also pointed out that the measurement came from just one location. Fisher notes, “this is a region where there is volcanic activity, so this measurement may be due to a local heat source in the crust.”
Drill baby, drill
Fisher and his team used a hot-water drill to reach Lake Whillans and the sediments below. Hmm, a hot-water drill in the Antarctic – I didn’t think it would be so simple…
Then, they lowered a specialized thermal probe, designed and built at UC Santa Cruz, to measure the temperature of the sediments.
They measured temperatures at several different depths and found a rate of change in temperature nearly five times higher than they typically find on continents.
The geothermal heat flux measured was around 285 milliwatts per square meter. In English? Fisher compares it to the heat from one small LED Christmas-tree light per square meter.
I know what you are thinking. ‘That’s nothing’ but, you have to look at in the long-term. According to the researchers, the amount of meltwater produced at the base of the ice sheet at the drill site is about a half an inch per year.
The results of this study are just another piece of data that will help researchers try to figure out what will happen to the West Antarctic ice sheet in the future.
“It is important that we get this number right if we are going to make accurate predictions of how the West Antarctic ice sheet will behave in the future, how much it is melting, how quickly ice streams flow, and what the impact might be on sea level rise,” said Slawek Tulaczyk, co-author of the study published in the journal Science Advances. “I waited for many years to see a directly measured value of geothermal flux from beneath this ice sheet.”
Image credits: UCSC, NASA