The global cryosphere – all areas of frozen water on Earth – shrank 87,000 km² per year from 1979 to 2016 as a result of climate change.
The size of the land covered by frozen water is just as important as its mass. This is because the bright white surface effectively reflects sunlight, cooling the planet. Changes in the size or location of ice and snow can affect air temperature, sea level and ocean currents around the world.
The cryosphere is one of the most sensitive climate indicators and shows how the world is changing. Reducing its size concerns everyone, it is not a regional or local issue.
Xiaoqing Peng, physicist and geographer from Lanzhou University, first author of the study
The cryosphere contains nearly three-quarters of the Earth’s fresh water, and in some mountainous regions, shrinking glaciers threaten drinking water sources. Scientists have previously documented shrinking ice sheets, declining snow cover, and the loss of Arctic sea ice separately due to climate change. But no previous study has looked at the entire extent of the cryosphere above the Earth’s surface and its response to rising temperatures.
In the new work, scientists calculated the daily extent of the cryosphere and averaged these values to obtain annual estimates. Although the cryosphere expands and contracts with the seasons, the researchers found that the Earth’s cryosphere has shrunk since 1979, which correlates with rising air temperatures.
Shrinkage mainly occurred in the Northern Hemisphere – 102,000 km² per year. These losses are slightly offset by growth in the Southern Hemisphere, where the cryosphere expands by about 14,000 km² annually. The growth was recorded in sea ice in the Ross Sea around Antarctica, likely due to the nature of the winds and ocean currents and the addition of cold melt water from Antarctic ice sheets.
The new study is published in AGU Earth’s Future magazine.