page_title: Greenland ice sheet
section_title: Rate of change
hierarchical_section_title: Greenland ice sheet / Change of the ice sheet / Rate of change
caption_attribution_description: English: Nach Installation eines Radarreflektors beginnt ein Wissenschaftler mit der Aufnahme eines Radarprofils auf dem westgrönländischen Eisschild. English: After installation of a radar reflector a scientist starts to acquire a transect across the ice sheet of west Greenland using a ground penetrating radar device.
context_page_description: The Greenland ice sheet is a vast body of ice covering 1,710,000 square kilometres, roughly 79% of the surface of Greenland.
  It is the second largest ice body in the world, after the Antarctic ice sheet. The ice sheet is almost 2,900 kilometres long in a north-south direction, and its greatest width is 1,100 kilometres at a latitude of 77°N, near its northern margin. The mean altitude of the ice is 2,135 metres. The thickness is generally more than 2 km and over 3 km at its thickest point. In addition to the large ice sheet, isolated glaciers and small ice caps cover between 76,000 and 100,000 square kilometres around the periphery. If the entire 2,850,000 cubic kilometres of ice were to melt, it would lead to a global sea level rise of 7.2 m. The Greenland Ice Sheet is sometimes referred to under the term inland ice, or its Danish equivalent, indlandsis. It is also sometimes referred to as an ice cap.
context_section_description: Several factors determine the net rate of growth or decline. These are
  Accumulation and melting rates of snow in the central parts
  Melting of surface snow and ice which then flows into moulins, falls and flows to bedrock, lubricates the base of glaciers, and affects the speed of glacial motion. This flow is implicated in accelerating the speed of glaciers and thus the rate of glacial calving.
  Melting of ice along the sheet's margins (runoff) and basal hydrology,
  Iceberg calving into the sea from outlet glaciers also along the sheet's edges
  Explanation of accelerated glacial coastward movement and iceberg calving fails to consider another causal factor: increased weight of the central highland ice sheet. As the central ice sheet thickens, which it has for at least seven decades, its greater weight causes more horizontal outward force at the bedrock. This in turn appears to have increased glacial calving at the coasts. Visual evidence for increased central highland ice sheet thickness exists in the numerous aircraft that have made forced landings on the icecap since the 1940s. They landed on the surface and later disappeared under the ice. A notable example is the Lockheed P-38F Lightning World War II fighter plane Glacier Girl that was exhumed from 268 feet of ice in 1992 and restored to flying condition after being buried for over 50 years. It was recovered by members of the Greenland Expedition Society after years of searching and excavation, eventually transported to Kentucky and restored to flying condition.
  The IPCC Third Assessment Report (2001) estimated the accumulation to 520 ± 26 Gigatonnes of ice per year, runoff and bottom melting to 297±32 Gt/yr and 32±3 Gt/yr, respectively, and iceberg production to 235±33 Gt/yr. On balance, the IPCC estimates −44 ± 53 Gt/yr, which means that the ice sheet may currently be melting. Data from 1996 to 2005 shows that the ice sheet is thinning even faster than supposed by IPCC. According to the study, in 1996 Greenland was losing about 96 km³ or 23.0 cu mi per year in volume from its ice sheet. In 2005, this had increased to about 220 km³ or 52.8 cu mi a year due to rapid thinning near its coasts, while in 2006 it was estimated at 239 km³ (57.3 cu mi) per year.  It was estimated that in the year 2007 Greenland ice sheet melting was higher than ever, 592 km³ (142.0 cu mi). Also snowfall was unusually low, which led to unprecedented negative −65 km³ (−15.6 cu mi) Surface Mass Balance. If iceberg calving has happened as an average, Greenland lost 294 Gt of its mass during 2007 (one km³ of ice weighs about 0.9 Gt).
  The IPCC Fourth Assessment Report (2007) noted, it is hard to measure the mass balance precisely, but most results indicate accelerating mass loss from Greenland during the 1990s up to 2005. Assessment of the data and techniques suggests a mass balance for the Greenland Ice Sheet ranging between growth of 25 Gt/yr and loss of 60 Gt/yr for 1961 to 2003, loss of 50 to 100 Gt/yr for 1993 to 2003 and loss at even higher rates between 2003 and 2005.
  Analysis of gravity data from GRACE satellites indicates that the Greenland ice sheet lost approximately 2900 Gt (0.1% of its total mass) between March 2002 and September 2012. The mean mass loss rate for 2008–2012 was 367 Gt/year.
  A study published in 2020 estimated, by combining 26 individual estimates of mass balance derived by tracking changes in Greenland's ice sheet volume, speed and gravity as part of the Ice Sheet Mass Balance Inter-comparison Exercise, that the Greenland Ice Sheet had lost a total of 3,902 gigatons (Gt) of ice between 1992 and 2018 . The rate of ice loss has increased over time from 26 ± 27 Gt/year between 1992 and 1997 to 244 ± 28 Gt/year between 2012 and 2017 with a peak mass loss rate of 275 ± 28 Gt/year during the period 2007 and 2012.
  A paper on Greenland's temperature record shows that the warmest year on record was 1941 while the warmest decades were the 1930s and 1940s.  The data used was from stations on the south and west coasts, most of which did not operate continuously the entire study period
caption: Glaciologist at work
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