No Going Back in Antarctic Glaciers; Scientists

No Going Back in Antarctic Glaciers; Scientists

Antarctica is crumbling at its edges. Antarctic glaciers flow more rapidly to the ocean, accelerating the rate of global sea level rise, revealed NASA in its latest findings.

Two studies published Aug. 10 and led by researchers at NASA’s Jet Propulsion Laboratory in Southern California reveal unexpected new data about how the Antarctic Ice Sheet has been losing mass in recent decades.

In one study, published in the journal Nature, the researchers mapped how iceberg calving – the breaking off of ice from a glacier front – changed the Antarctic coastline over the last 25 years. They  found that the edge of the ice sheet has been shedding icebergs faster than the ice can be replaced. This surprise finding doubles previous estimates of ice loss from Antarctic’s floating ice shelves since 1997, from 6 trillion to 12 trillion metric tons. Ice loss from calving has weakened the ice shelves and allowed Antarctic glaciers to flow more rapidly to the ocean, accelerating the rate of global sea level rise.

In the other study published in Earth System Science Data, the researechers details how the thinning of Antarctic ice spread from the continent’s outward edges into its interior. They found that this almost doubled in the western parts of the ice sheet over the past decade.

ANTARTICA; ICEBERG CALVING

Lead author of the calving study and JPL scientist Chad Greene said “Antarctica is crumbling at its edges.”

“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,” the scientist said.

Antarctic glaciers flow to the ocean, where they end in floating ice shelves up to two miles thick and 500 miles across. These ice shelves act like buttresses to glaciers. They keep the ice from simply sliding into the ocean. When ice shelves are stable, they have a natural cycle of calving and replenishment that keeps their size fairly constant over the long term. However, the scientists said that warming ocean in recent decades has been destabilizing Antarctica’s ice shelves by melting them from below, making them thinner and weaker.

The researchers noted that losses from calving outpaced natural ice-shelf growth so greatly. As such, they raise doubts if Antarctica could grow back to its pre-2000 extent by the end of this century. “In fact, the findings suggest that greater losses can be expected: Antarctica’s largest ice shelves all appear to be headed for major calving events in the next 10 to 20 years,”they said.

For the new study, Greene and his co-authors synthesized satellite imagery of the continent in visible, thermal infrared (heat), and radar wavelengths since 1997. Combining these measurements with an understanding of ice flow gained from an ongoing NASA glacier-mapping project, they charted the edges of ice shelves around 30,000 linear miles (50,000 kilometers) of Antarctic coastline.

ANTARCTICA; MAPPING 36 YEARS OF ICE LOSS

The study reveals how long-term trends and annual weather patterns affect the ice. It showed the rise and fall of the ice sheet as subglacial lakes regularly fill an empty miles below the surface. “Subtle changes like these, in combination with 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,” said JPL’s Johan Nilsson, lead author of the study.

About ten per cent of the land area on Earth is estimated to be covered with glacial ice. Almost 90 per cent is in Antarctica, while the remaining ten per cent is in the Greenland ice cap. However, climate change andf global warming has led to massive melting of the glacial ice. The melting of ice influences ocean currents, as massive amounts of very cold glacial-melt water entering warmer ocean waters is slowing ocean currents. And as ice on land melts, sea levels will continue to rise.

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