The ocean is melting Greenland from the bottom up
In short: While surface melt captures headlines, the most significant driver of ice loss is hidden beneath the waves. Scientists are now diving into sub-glacial cavities to measure how warming seawater undermines the very foundations of the world's largest ice sheets.
On Greenland’s Petermann Glacier, researchers are deploying sonar and robotic systems to reach the seawater directly beneath the floating ice tongue. This mission targets one of the least visible but most critical processes: ocean-driven melt from below. By profiling temperature, salinity, and depth within these hidden cavities, the team aims to quantify how warming waters accelerate the disintegration of the glacier's base. The expedition involves navigating dangerous crevasses and establishing camps directly on the ice to deploy these sensors. These instruments are essential for capturing data in a remote environment where direct measurements remain rare.
This focus on sub-glacial dynamics is supported by a massive satellite record spanning over 50 years. Data from the IMBIE team shows that since the 1970s, Greenland and Antarctica have lost 11,309 billion metric tons of ice, contributing to a global sea level rise of more than 3 centimeters. Crucially, the study reveals that 84% of this loss is driven by glaciers speeding up and pouring into the ocean—a dynamic response to warming waters—rather than surface melting, which accounts for only 16%. Greenland's rate of loss accelerated from roughly 60 billion metric tons annually in the 1980s to 264 billion metric tons during the 2010s. This period was specifically characterized by frequent and extreme summer melt events.
The urgency of these findings is underscored by geological history. Approximately 7,000 years ago, a gentle natural warming phase within the Holocene caused this elevated section of the ice sheet to vanish entirely, as shown by modern drilling at Prudhoe Dome. Because the dome vanished when temperatures were only 3 to 5 degrees Celsius warmer than today, it suggests that current human-induced warming could trigger rapid and potentially irreversible retreat of what was once considered stable ice. To identify the final moment of light exposure for sediment, experts applied luminescence dating to samples retrieved at a depth of 1,669 feet. These chemical signatures help pinpoint exactly when the ice sheet disappeared during past climate cycles.
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Sources
- Summary by Intellect · source: The Greenland Glacier Mission to Measure Melt From Below | SLICE EARTH | FULL DOC
- Also: Speeding glaciers drive half a century of polar ice loss
- Also: Greenland ice completely melted 7,000 years ago and could happen again
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