An analysis of new Antarctic research, including the first map of iceberg calving, has doubled the previous estimate of ice shelf loss and sheds light on how the continent is changing. Ice loss from Antarctica's floating ice shelves has doubled from 6 trillion metric tons to 12 trillion metric tons since 1997.
Antarctica, the frozen continent, is changing fast.
Antarctica’s ice loss will accelerate as the climate warms, which poses the greatest uncertainty in forecasting global sea level rise. Scientists from NASA’s Jet Propulsion Laboratory in Southern California revealed new data on the Antarctic Ice Sheet’s mass loss in recent decades in two studies published on Aug. 10.
A study published in Nature offers insight into how icebergs have calved off glacier fronts over the last 25 years, changing the Antarctic coastline. Researchers found that icebergs are being shed faster than ice can be replaced on the ice sheet’s edge.
According to this discovery, ice loss from Antarctica’s floating ice shelves has doubled from 6 trillion metric tons to 12 trillion metric tons since 1997.
As a result of ice-shelf calving, Antarctic glaciers are flowing more rapidly into the ocean, accelerating global sea level rise.
According to another study published in Earth System Science Data, Antarctic ice is shrinking from its outward edges to its interior as ocean water melts, nearly doubling in the western parts of the ice sheet over the past decade as a result of ocean water melting.
Together, the two reports provide the most comprehensive picture yet of the changing landscape of the frozen continent.
“Antarctica is crumbling at its edges,” says JPL scientist Chad Greene, lead author of the calving study. “And when ice shelves dwindle and weaken, the continent’s massive glaciers tend to speed up and increase the rate of global sea level rise.”
There are large floating ice shelves in the Antarctic ocean, whose thickness can reach 2 miles (3 kilometers) and their width can reach 500 miles (800 kilometers). The ice shelves act as buttresses to glaciers, keeping them from being simply swept away by the ocean. The long-term stability of ice shelves is maintained by a natural cycle of calving and replenishment.
However, Antarctica’s ice shelves have become thinner and weaker in recent decades due to warming oceans. There has been no comprehensive assessment of how climate change might affect calving around the continent until this study, which measures the thinning process by measuring the height of the ice.
Several reasons exist, including the difficulty in interpreting satellite imagery.
“You can imagine looking at a satellite image and trying to figure out the difference between a white iceberg, white ice shelf, white sea ice, and even a white cloud. That’s always been a difficult task. But we now have enough data from multiple satellite sensors to see a clear picture of how Antarctica’s coastline has evolved in recent years,” said Greene.
Using satellite imagery of the continent in visible, thermal infrared (heat), and radar wavelengths, Greene and his associates performed a new analysis of satellite imagery of the continent from 1997 onwards. These measurements, coupled with information obtained from a NASA glacier-mapping project, allowed the researchers to map the edges of ice shelves across 30,000 linear miles (50,000 kilometers) of Antarctica’s coast.
Researchers believe Antarctica is unlikely to grow back to its pre-2000 extent by the end of this century due to calving losses outpacing natural ice-shelf growth.
A decade to twenty years from now, Antarctica’s largest ice shelves are all expected to undergo major calving events, suggesting greater losses are likely.
The JPL study reveals the longest continuous record of change in the height of the ice sheet since 1985 by combining nearly 3 billion data points from seven spaceborne altimetry instruments. They used laser and radar measurements of ice elevation to make the highest-resolution maps of ice loss ever made.
In addition to showing long-term trends, it also highlights how weather patterns affect the ice annually. As subglacial lakes regularly fill and empty miles beneath the surface, it shows how the ice sheet rises and falls.
“Subtle changes like these, in combination with an improved understanding of long-term trends from this data set, will help researchers understand the processes that influence ice loss, leading to improved future estimates of sea level rise,” explained JPL’s Johan Nilsson, lead author of the study.
It took NASA’s servers thousands of hours to analyze and synthesize the massive archive of measurements into a single, high-resolution set.
Nevertheless, Nilsson says condensing the data could lead to big breakthroughs in understanding our planet and preparing for climate change’s future impacts.
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