Satellite Imagery Reveals Antarctic Ice Loss is Double Previous Estimates

The 200-foot-tall (60-meter-tall) front of Antarctica’s Getz Ice Shelf is marked with fissures where icebergs are likely to break off or calve in this 2016 photo. The first calving estimate Antarctica revealed that since 1997, ice shelves in Antarctica have lost as much ice to calving as to melting. | Credits: NASA/GSFC/OIB

New Antarctica research found in two separate studies referencing multiple optical and radar satellite sensors has revealed Antarctica ice loss is much worse than previous estimates.

Two studies that investigated calving – the term that describes the breaking off of chunks of ice from the edge of a glacier – found that ice crumbling in Antarctica is actually double previous estimates and details the evolution from the continent. Both studies were conducted by researchers at NASA’s Jet Propulsion Laboratory (JPL) in Southern California and reveal what NASA says are “unexpected” new data on how the Antarctic ice sheet lost mass in recent decades.

The first study, published in Nature and titled Antarctic calving loss rivals ice-shelf thinning, maps how iceberg calving has altered the coastline of the polar continent over the past 25 years.

“Antarctic’s ice shelves help control the flow of glacial ice as it flows into the ocean, meaning the rate of global sea level rise is subject to structural integrity of these fragile, floating extensions of the ice sheet,” the researchers write. .

“So far, data limitations have made it difficult to monitor large-scale cycles of ice shelf growth and retreat, and the full impact of recent changes in the calving front on shelf strengthening. of ice was not included.”

The researchers combined data from several optical and radar satellite sensors and show that from 1997 to 2021, Antarctica experienced a net loss of 36,701 square kilometers (1.9%) of sea ice area which they say cannot be fully recovered until the next series of great events. calving events.

“The mass loss associated with the retreat of the ice front has been approximately equal to the change in mass due to the thinning of the pack ice over the last quarter century, which means that the total mass loss is nearly twice that of that which could be measured by altimetry surveys alone,” they say, adding that further ice retreat could have a significant impact on sea level rise in the future.

Previously, studying satellite images of Antarctica was difficult.

“You can imagine looking at a satellite image and trying to figure out the difference between a white iceberg, white ice floe, white ice floe and even a white cloud. This has always been a difficult task,” says Chad Greene, JPL scientist and lead author of the study.

Ice changes in Antarctica
Antarctic ice sheet elevation changes from 1985 to 2021 are shown. Ice height decreases (red) as the ice sheet melts on contact with seawater; it rises (blue) where accumulation exceeds fusion. Ice shelves are shown in grey. Missions that provided data are listed at the bottom. | Credits: NASA/JPL-Caltech

“But we now have enough data from multiple satellite sensors to get a clear picture of how the Antarctic coastline has changed in recent years.”

NASA says scientists don’t think it’s possible Antarctica could regrow the ice it’s lost since before the year 2000 before the end of the century and instead it’s more likely to experience “major” calving events. in the next 10 to 20 years.

The second study, published in Earth System Science Data, goes further and shows how Antarctic ice thinning has spread from the outer edges of the continent to its interior, nearly doubling the western part of the ice sheet over the past 10 last years.

“The greatest uncertainty in future projections of sea level change comes from the uncertain response of the Antarctic ice sheet to warming oceans and atmosphere,” the study, titled Antarctic Ice Sheet Elevation Change: 1985 to 2020find.

Scientists combined nearly three billion data points from seven satellite instruments to produce the longest continuous data set of ice sheet evolution, NASA reports.

“The ice sheet gains about 2000 km3 of ice from precipitation each year and loses a similar amount through the discharge of solid ice into the surrounding oceans. Numerous studies have shown that the ice sheet is currently out of long-term equilibrium, losing mass at an accelerating rate and increasing sea level rise.”

There is considerable uncertainty within the scientific community when it comes to predicting sea level rise as a result of changes to the Antarctic ice sheet. It took years to analyze this new data – thousands of hours of time on NASA servers – which Johan Nilsson of JPL, lead author of the study, says is well worth the effort.

“Condensing the data into something more broadly useful can bring us closer to the big breakthroughs we need to better understand our planet and help us prepare for the future impacts of climate change,” he says.

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