Antarctica

Scientists solve a Southern Ocean climate change mystery

An iceberg in the Southern Ocean, where deeper ocean layers are warming and freshening.
Iceberg in the Southern Ocean, where deep ocean waters are seeing rising temperatures and a trend toward lower salinity values. Photo: Freedive Antarctica/Barcroft Media via Getty Images

The Southern Ocean is the planet's main heat and greenhouse gas sink, and without it, global warming would be a lot worse. It's also one of the least-observed and understood parts of the global ocean, due largely to its remoteness and competing influences there, from Antarctic sea ice to changing weather patterns and the slow healing of the stratospheric ozone layer.

The context: We've long known that on the ocean surface, parts of the Southern Ocean have been cooling over time, while deeper waters have been warming and freshening. But why these disparate trends have occurred has eluded scientists.

Sea level rise: New study adds to worries about East Antarctica

Blocks of ice drift on the water off the coast of Collins glacier on King George Island, Antarctica on February 1, 2018.
Blocks of ice drift on the water off the coast of Collins glacier on King George Island, Antarctica on February 1, 2018. Photo: MATHILDE BELLENGER/AFP/Getty Images

A new study of the East Antarctic Ice Sheet's response to past warm periods has unsettling implications for the magnitude and timing of sea level rise as global warming continues. Until recently, most of scientists' concerns were about the instability of Greenland and the West Antarctic Ice Sheet, but that is starting to change.

Why it matters: The study, published Wednesday in the journal Nature, reveals the history of ice retreat and expansion in the Wilkes Subglacial Basin, in the southeastern corner of the East Antarctic Ice Sheet. The fate of the Antarctic Ice Sheet represents one of the largest uncertainties in climate science.