Changes in Antarctic melting patterns and the wet state of Arctic glaciers are pushing global warming toward the upper limit predicted by climate models.
A new study led by scientists at the University of Michigan shows that the Arctic has lost about 25% of its cooling capacity since 1980 due to shrinking sea ice and reduced reflectance. This has resulted in a loss of up to 15% of global cooling capacity.

Using satellite measurements of cloud cover and solar radiation reflected from sea ice between 1980 and 2023, the researchers found that the percentage decrease in sea ice cooling capacity is about twice the percentage decrease in annual average sea ice area in both the Arctic and Antarctic regions. The additional warming effect of this change in sea ice cooling capacity is closer to the upper bound of climate model projections.

“When we use climate modeling to quantify how sea ice melting is affecting the climate, we typically run a century of simulations before we get an answer,” said Mark Flenner, professor of climate and space sciences and engineering and corresponding author of the study, published in the journal Geophysics. The research papers.

“We’ve now reached the point where we have a long enough satellite record to assess the sea ice-climate feedback using measurements.”

Since 1980, the Arctic has seen the largest and most sustained decline in sea ice cooling capacity, but until recently the Antarctic appeared more resilient to climate change. Sea ice cover remained relatively stable from 2007 to the 2010s, during which time the cooling capacity of Antarctic sea ice actually increased.

Stabilization and reduction of ice in Antarctica

That view changed dramatically in 2016, when one of the continent’s largest ice shelves melted away an area larger than Texas. Antarctica also lost sea ice, and its cooling capacity did not recover, according to a new study. As a result, 2016 and the seven years that followed were the weakest cooling effects on global sea ice since the early 1980s.

In addition to ice sheet loss, the remaining ice is also becoming less reflective, as warmer temperatures and increased precipitation create thinner, wetter ice and more melt pools that reflect less solar radiation. This effect has been most pronounced in the Arctic, where sea ice becomes less reflective during the brightest parts of the year, and the new study raises the possibility that it could be a major factor in Antarctica as well, in addition to sea ice loss.

“Changes in Antarctic sea ice since 2016 increase the warming feedback from sea ice loss by 40%. If we do not take into account this change in the radiative effect of Antarctic sea ice, we could lose a significant part of the total global energy absorption,” said Alisher Duspaev, a doctoral student in physics and first author of the study.

The research team hopes to provide the climate community with their updated estimates of the cooling capacity of sea ice and the climate feedback from less reflective ice through a website that is updated when new satellite data becomes available.

“Climate change adaptation plans should include these new figures in the overall calculation of how quickly and how widely the effects of radiative cooling of the cryosphere will affect the global climate system,” said Aku Riihelja, a research professor at the Finnish Meteorological Institute and co-author of the study.