Earth's frozen water is shrinking 87 thousand square kilometers per year

Ground Report | New Delhi: Earth's frozen water is shrinking; 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 Earth's surface covered by sea ice, snow, and frozen ground. It is published in the magazine Earth's Future of the AGU (American Geophysical Union).

Earth's frozen water is shrinking

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 can alter air temperatures, changing sea levels, 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," first author Xiaoqing Peng, a physical geographer at Lanzhou University, said in a statement. "Its change in size represents a major global change, rather than a regional or local problem."

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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.

Earth's cryosphere has generally contracted since 1979

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.

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Average first day freezing comes about 3.6 days

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.

Estimates showed that the cryosphere around the world was not only shrinking but was also freezing in many areas in a short period of time. The average first day of freezing comes about 3.6 days later than after 1979, while the ice melts about 5.7 days earlier.

Sean Marshall, a glaciologist at the University of Calgary, said this type of analysis is a good plan for a global index or measurement of climate change. Using these data the next step will be to investigate how much snow and ice cover there will be on Earth and for how long. To see how changes in albedo affect climate on a seasonal or monthly basis and how it is changing over time. (Earth's frozen water is shrinking)

Earth's frozen water is shrinking climate change

To estimate the extent of the cryosphere around the world, the researchers divided the Earth's surface into grid systems. The study is published in AGU's journal Earth Future.

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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