“Think about spraying an icy road with a jet of salty warm water—you don’t need meters of that salt water to melt ice rapidly.” Eric Rinot
Thwaites Glacier is a massive cap of ice the size of Florida in the highly vulnerable West Antarctic ice sheet. It currently contributes four percent to the rise of the global sea level. Although the glacier has only been studied since 2018, satellite and radar data have provided valuable information critical to understanding the worrying potential sea level rise on the world’s coastlines.
We know meltwater from warm ocean currents is destructive to the Antarctic Circumpolar Current, a critical part of the planet’s overturning circulation. The exchange of heat and CO2 between the Southern Ocean and the atmosphere is essential to the stability of Antarctic ice sheets. From paleoclimate data, the current slows during glacial periods and accelerates during interglacials. That would mean that the Southern Ocean will store less CO2 in the future and bring even more heat to Antarctica. That active process may slow the current by forty percent within three decades—a terrifying threat to the stability of the Earth’s climate.
As far as we know, all the damage to this widely studied glacier occurs under the ocean’s surface. Warm water driven by winds erodes the base of the ice’s marine extension, creating cavities where the ice can reach further and create verticle cracks that rise to the ice surface. (An example is illustrated by the embed from Christopher Cartwright below.) The warming water underbelly ice damage is assumed to end at the grounding line where the ocean meets the bedrock. Not anymore; the warm water (mid-30s F) is a tide-driven daily intrusion that reaches miles inland, according to recent radar data.
Anupama Chandrasekaran writes in EOS.
Most ice sheet simulations have not accurately predicted Thwaites’s recent retreat because they assume that a glacier’s grounding line is fixed. But recent research on Thwaites and other glaciers has shown that these boundaries between floating ice and ice that is grounded on the seafloor shift with the daily tide.
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Using satellite radar data from the private company ICEYE collected over 3 months in 2023, a team of glaciologists created a detailed image of Thwaites’s shifting grounding line by looking at how the glacier surface bobbed up and down throughout the day.
“The difference with this study is that they were having multiple measurements per day,” said Alex Brisbourne, a glaciologist at the British Antarctic Survey who was not involved with the research. “So what they could see [were] these really short-timescale processes.”
Satellites can see only the surface of the ice, but because the ice is compacted, tiny vertical movements signal that the glacier bed must be rising too, wrote Eric Rignot in an email. Rignot is a glaciologist at the University of California, Irvine, and NASA’s Jet Propulsion Laboratory and first author of the study.
The team found that the ice rose and sank in sync with the tides. The data suggested that the grounding line migrated up to 6 kilometers (3.7 miles) inland during an average high tide.
When the tides were particularly high, the glacier’s uplift suggested that a thin layer of seawater up to 10 centimeters (4 inches) deep pushed another 6 kilometers (3.7 miles) inland. The researchers think that this extra water may be causing more melting than current estimates predict because it replaces cold melted fresh water that lines the base of the glacier with warmer, salty seawater.
Dr. Sarah Adams is a scientist and science communicator who makes complex topics accessible to all. Her articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
