Earth Lost 12.5 Trillion Tons of Polar Ice Since 1979 as Sea Levels Rose 1 Inch

Q: If warming air isn't the main culprit for melting ice sheets, what hidden ocean force is pushing them toward an irreversible tipping point?

The main hidden force is warm ocean water intruding beneath and alongside marine-terminating glaciers, where it melts them from below, erodes their edges, and speeds their flow into the sea. The study says about five-sixths of Greenland and Antarctica’s ice loss since 1979 was not driven mainly by warmer air at the surface, but by ocean-driven glacier imbalance. In practice, relatively warm subsurface water reaches glacier fronts and ice shelves, undercutting them in fjords and along the Antarctic coast. In West Antarctica, that often means warm Circumpolar Deep Water; in Greenland, it includes warm Atlantic-origin water entering fjords. That process matters because it removes the floating ice tongues and ice shelves that help brace inland ice. Once that buttressing weakens, glaciers accelerate, retreat inland, and discharge more ice into the ocean. Scientists describe this as dynamic ice loss, and it is the mechanism most associated with instability and possible tipping points in places such as Thwaites and Pine Island in West Antarctica and Jakobshavn in Greenland. Researchers say this is why the threat can become hard to reverse: ocean heat does not just melt ice at the surface, it destabilizes the glacier system itself. Even if air temperatures stop rising as quickly, the ocean can keep delivering heat to glacier bases for years or decades, sustaining retreat and raising the risk of self-reinforcing collapse in vulnerable basins.

3 articles · Updated · KSL.com · Sep 20

12.5 trillion tons of ice melted from Greenland and Antarctica between 1979 and 2023, adding nearly 3 quadrillion gallons of water and lifting global sea levels by about 1 inch, a new study found.
Five-sixths of that loss came from warmer ocean water eroding ice sheets from below and the sides, with researchers saying the acceleration is tied to climate change rather than short-term weather.
The melt was limited through the 1970s, 1980s and much of the 1990s, then surged in the 2010s; a 2020-2023 pause was attributed largely to East Antarctica snowfall offsetting losses elsewhere.
Each third of an inch of sea-level rise exposes another 2 million to 3 million people to annual flooding, and scientists said the recent lull has already given way to renewed acceleration in newer measurements.
Using 45 surveys and 27 satellites, the international team said the dominance of fast-moving, dynamic ice loss raises concern about longer-term instability even if planetary warming is eventually curbed.