New observations from ICESat-2 show remarkable Arctic sea ice thinning in just three years —

Over the previous 20 years, the Arctic has misplaced about one-third of its winter sea ice quantity, largely as a consequence of a decline in sea ice that persists over a number of years, known as multiyear ice, in accordance with a brand new examine. The examine additionally discovered sea ice is probably going thinner than earlier estimates.

Seasonal sea ice, which melts utterly every summer time relatively than accumulating over years, is changing thicker, multiyear ice and driving sea ice thinning tendencies, in accordance with the brand new analysis.

Arctic sea ice snow depth is estimated, for the primary time, from a mix of lidar (ICESat-2) and radar (CryoSat-2) knowledge. Utilizing these estimates of snow depth and the peak of sea ice uncovered above water, the examine discovered multiyear Arctic sea ice has misplaced 16% of its winter quantity, or roughly half a meter (about 1.5 ft) of thickness, within the three years because the launch of ICESat-2.

The examine was revealed within the AGU journal Geophysical Analysis Letters, which publishes short-format, high-impact papers with implications that span the Earth and house sciences.

“We weren’t actually anticipating to see this decline, for the ice to be this a lot thinner in simply three brief years,” stated lead examine creator Sahra Kacimi, a polar scientist on the California Institute of Know-how’s Jet Propulsion Laboratory.

Scientists make satellite tv for pc estimates of sea-ice thickness utilizing snow depth and the peak of the floating ice above the ocean floor. Snow can weigh ice down, altering how ice floats within the ocean. The brand new examine in contrast ice thickness utilizing new snow depths from satellite tv for pc radar and lidar to earlier ice thickness and snow depth estimates from local weather data. The researchers discovered utilizing climatology-based estimates of snow depth can lead to overestimating sea-ice thickness by as much as 20%, or as much as 0.2 meters (0.7 ft).

“Arctic snow depth, sea ice thickness and quantity are three very difficult measurements to acquire,” stated Ron Kwok, a polar scientist on the College of Washington’s Utilized Physics Laboratory who co-authored the brand new examine. “The important thing takeaway for me is the exceptional lack of Arctic winter sea ice quantity — one-third of the winter ice quantity misplaced over simply 18 years — that accompanied a broadly reported lack of outdated, thick Arctic sea ice and decline in end-of-summer ice extent.”

“That is the primary time anybody has a number of years’ price of knowledge from the distinction between lidar and radar knowledge for snow depth,” stated Robbie Mallett, a polar ice researcher at College School London who was not concerned within the examine. “It is a actually helpful replace on how ICESat-2 is performing.”

The examine used an 18-year document of sea-ice observations from ICESat and the newer ICESat-2 and CryoSat-2 satellites to seize month-to-month adjustments in Arctic sea-ice thickness and quantity, to supply context for sea ice thickness estimates from 2018 to 2021. The 18-year document confirmed a lack of about 6,000 cubic kilometers of winter ice quantity, largely pushed by the change from predominantly multiyear ice to thinner, seasonal sea ice.

Older, multiyear ice tends to be thicker and subsequently extra proof against melting. As that “reservoir” of outdated Arctic sea ice is depleted and seasonal ice turns into the norm, the general thickness and quantity of Arctic sea ice is predicted to say no. “Present fashions predict that by the mid-century we will anticipate ice-free summers within the Arctic, when the older ice, thick sufficient to outlive the soften season is gone,” Kacimi stated.

“That is actually outdated ice we’re shedding at fairly a daunting charge,” Mallett stated.

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