A rapid shift in ocean currents could imperil the world’s largest ice shelf
The Ross Ice Shelf was expected to stabilize major coastal glaciers well into the future
Antarctica’s largest ice shelf, buttressing a dozen major glaciers and slowing their flow into the ocean, may be surprisingly sensitive to warming.
Several thousand years ago, the Ross Ice Shelf and the glaciers feeding it thinned dramatically, causing sea level to rise. A new study, published April 23 in Nature Communications, suggests 🔥this was triggered by a rearrangement of ocean currents — just half a degree Celsius.
“This suggests that it’s actually not that hard to drive change here,” says Christina Hulbe, a glaciologist at the University of Otago in Dunedin, New Zealand, who was not involved in the study. With ocean temperatures in the region temporarily spiking as much as 0.1 to 0.2 degrees above normal in the last seven years, “we’re heading into an ocean that could do it.”Ocean currents have kept Ross Ice Shelf stable
Even as parts of Antarctica hemorrhage ice, scientists have long believed the Ross Ice Shelf would hold steady. This slab of ice the size of Spain extends off the coastline and floats on waters south of New Zealand. If the Ross Ice Shelf retreated today, it would open a crucial back door to the West Antarctic Ice Sheet — already losing substantial ice from Thwaites and Pine Island Glaciers — allowing warm ocean currents to melt it from two sides. If the sheet melted entirely, it would raise sea levels enough to put Miami; Newark, N.J.; Charleston, S.C.; and the Bahamas . Currently, the Ross Ice Shelf is shielded from that melting by a natural oceanic conveyor belt. It operates just beyond the shelf’s outer, ocean-facing edge. As ocean water migrates through this area, bitter-cold air causes its surface to freeze, forming a steady procession of meter-thick sea ice. As the sea ice forms, it ejects salt. The water beneath it becomes saltier and denser, and sinks. Roughly 30,000 cubic kilometers of this cold, dense water forms each year — more than four times the annual flow of the Amazon River. It sinks to the seafloor like a steady waterfall where the outer edge of the ice shelf meets the ocean, blocking the entry of warm water from further north.“That’s why we see really low melt rates there today,” says Daniel Lowry, a climate scientist at GNS Science in Lower Hutt, New Zealand, who coauthored the new study. Even as esportiva bet:some parts of West Antarctica are for decades (SN: 6/9/22).