Tuesday, October 19

Earth’s cryosphere is shrinking 87,000 km2 per year

The Earth's cryosphere is shrinking 87,000 km2 per year.

Earth’s cryosphere is shrinking 87,000 km2 per year.

The global cryosphere, all areas of frozen water on Earth, shrank by approximately 87,000 square kilometers per year on average between 1979 and 2016, due to climate change.

It is the result of the first global estimate of the surface of the Earth covered by sea ice, snow and frozen ground. It is published in the journal Earth’s Future of the AGU (American Geophysical Union).

The extent of the land covered by frozen water is as important as its mass because the bright white surface reflects sunlight so effectively, cooling the planet. Changes in the size or location of ice and snow They can alter air temperature, change sea level, and even affect ocean currents around the world.

“The cryosphere is one of the most sensitive climate indicators and the first to demonstrate a changing world,” he said it’s a statement first author Xiaoqing Peng, a physical geographer at Lanzhou University. “Its change in size represents a major global change, rather than a regional or local problem.”

The cryosphere contains almost three-quarters of the Earth’s fresh water, and in some mountainous regions, shrinking glaciers threaten the supply of drinking water. Many scientists have documented shrinking ice sheets, shrinking snow cover, and the loss of Arctic sea ice individually due to climate change. But no previous study has considered the full extent of the cryosphere over the Earth’s surface and its response to warming temperatures.

Peng and his co-authors from Lanzhou University calculated the daily extent of the cryosphere and averaged those values ​​to obtain annual estimates. While the extent of the cryosphere grows and shrinks with the seasons, they found that the average area covered by Earth’s cryosphere has generally contracted since 1979, which correlates with rising air temperatures.

The contraction occurred mainly in the northern hemisphere, with a loss of approximately 102,000 square kilometers, each year. Those losses are slightly offset by growth in the southern hemisphere, where the cryosphere expanded by about 14,000 square kilometers (5,400 square miles) a year. This growth occurred primarily on sea ice in the Ross Sea around Antarctica, likely due to patterns of wind and ocean currents and the addition of cold meltwater from the Antarctic ice sheets.

Estimates showed that not only was the global cryosphere shrinking, but many regions remained frozen for less time. The average first day of freezing now occurs about 3.6 days later than in 1979, and the ice is melting about 5.7 days earlier.

To compile their global estimate of the extent of the cryosphere, the authors divided the planet’s surface into a grid system. They used existing data sets of the global extent of sea ice, snow cover, and frozen ground to classify each cell in the grid as part of the cryosphere if it contained at least one of the three components. They then estimated the extent of the cryosphere on a daily, monthly and yearly basis and examined how it changed over the 37 years of their study.

The authors say that the global dataset can now be used to further investigate the impact of climate change on the cryosphere and how these changes impact ecosystems, carbon exchange, and the timing of plant life cycles. and the animals.


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