“Part of this salty groundwater could be remnant from when those sediments were initially deposited,” Gustafson proposed. “But then some of the salt in the groundwater could also come from times when the ice sheet grew, but then it retreated again, and ocean water came in.”


This was all hypothetical until now, and the researchers say they are the first to use magnetotellurics to actually image the subglacial groundwater.

“The scientific community has known for a while that there is a thick layer of marine sediments beneath much of the West Antarctica ice sheet, but we don’t know much about how the ice sheet is influenced by deep groundwater, which the new study shows is saline,” Poul Christoffersen wrote in an email. Christoffersen, who called the new paper “fascinating,” is a glaciologist at the Scott Polar Research Institute at the University of Cambridge and was unaffiliated with this project. He continued: “The new study also shows the freshwater produced by melting at the bottom of the ice sheet has penetrated several hundred meters into the groundwater system since the ice sheet formed, and that salt and solutes likely also flowed into the ice sheet’s basal drainage system.”


The groundwater beneath the ice stream could be playing a pivotal role in how the stream carries ice toward the sea. “I have this analogy: ice streams are like slip-and-slides,” Gustafson said. “So, if you have water on a slip-and-slide, you can slide pretty quickly. But if there’s less water or no water, you’re not going to slide very far.”

Brad Lipovsky of the University of Washington’s College of the Environment echoed Gustafson’s description. He told me in a phone call: “In the first few meters underneath the glacier, the properties there control how fast the ice flows in a direct way: [if] your glacier is sitting on top of a bunch of wet clay, it’s more slippery and the ice flows faster.”


These findings have potential implications for the rest of the continent. Gustafson said different pockets of subglacial groundwater could be found underneath ice streams all over Antarctica. “There are observations from surrounding Antarctica, that suggest that these sediments are present beneath [other] ice streams,” she said. “I would bet that these aquifers are common features throughout Antarctica.”

While glaciers cover only 10% of Earth, the glaciers in Antarctica account for 85% of that coverage. Depending on how this groundwater behaves, it could help ice flow faster or slower into the ocean. The researchers suggest that when the system is stable, groundwater will drain into the Southern Ocean as more meltwater infiltrates the sediments. But if the ice streams were to lose mass under the rising temperatures of climate change, their reduced pressure on the sediments beneath them could allow more groundwater to rise to the surface, further lubricating the base of the stream and increasing its velocity, threatening the future of the continent’s ice cover.