“Couldn’t be more timely”: new data record shows marked decline in sea ice

Global sea ice decline has been shown in unprecedented detail in a new data model released by European researchers.

Researchers from the European Space Agency Climate Change Initiative’s sea ice division have now released a three-decade-long data record that shows a detailed recession in sea ice coverage across the Arctic.

Ice melt in polar regions influences global weather and ocean currents, and local wildlife. In the Arctic, it can also impact quality-of-life among indigenous communities.

The ESA pushes high-quality imaging obtained by instruments mounted to orbiting US Defence Department’s meteorological monitoring satellites through a specialised algorithm, which is then verified against data from ESA’s Copernicus Sentinel satellite system.

This process results in highly detailed Arctic sea ice mapping, particularly at the water’s edge, and is expected to be adopted by scientists seeking to understand the impact ice loss has on ocean and atmospheric systems.

“All around the world, modelling groups are developing the next generation of climate models that aim at a grid resolution of just a few kilometres,” says Dirk Notz, a climatologist from Hamburg University.

“To evaluate these models, and to learn how well we understand the processes that drive the ongoing sea-ice loss on these scales, having access to satellite data with a similar spatial resolution is absolutely crucial, [it] couldn’t be more timely.”

A second dataset characterising late summer Arctic sea ice shows a reduction of more than three million square kilometres of coverage over the last four decades.

Confirmed: circulating currents are slowing

At the other end of the planet, scientists have confirmed earlier predictions of slowing deep-ocean currents in Antarctica.

Earlier this year, increased meltwater from thawing polar ice was predicted to reduce the speed of nutrient overturning processes in the Southern Ocean by 40%.

Each year, 250 trillion tonnes of cold, oxygen-rich salt water descends to the Antarctic seafloor, bringing nutrients from dead animals with it. This water is then pumped around the planet, influencing ocean temperatures and rainfall patterns.

Melting freshwater ice dilutes and disrupts the process and deprives marine ecosystems of essential nutrition. Scientists have confirmed Antarctic overturning is now 30% slower than it was in the 1990s.

“We’re used to the idea that melting of the Antarctic Ice Sheet causes sea level rise. But this work also shows us that the impacts of melting glaciers in Antarctica extend all the way to the deep sea,” says study co-author Dr Steve Rintoul. “It’s affecting climate and ocean chemistry, as well as sea level.”