Glaciers are formed from snow that has compacted to form ice, which can deform and flow downhill to lower and warmer altitudes where it melts. If the glacier terminates in a lake or the ocean, ice loss also occurs through melting where ice and water meet or by calving of the glacier front to form icebergs. Glaciers are sensitive to changes in temperature, precipitation, and sunlight, as well as other factors such as changes in basal lubrication, warming ocean waters, or the loss of buttressing ice shelves.
According to the World Glacier Monitoring Service, in the hydrological year 2019-2020, the 40 or so glaciers with long-term observations experienced an average mass balance of -0.98 m water equivalent (m w.e39), less than in the record years 2018 and 2019, but still ranking as the 5th most negative mass balance year on record, for the period 1950-2020 (WHO).
Credit: H. Raab /