Ice Sheet Mass Balance Inter-comparison Exercise

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The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) is an international scientific collaboration attempting to improve estimates of the Antarctic and Greenland ice sheet contribution to sea level rise and to publish data and analyses concerning these subjects. IMBIE was founded in 2011 and is a collaboration between the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) of the United States, and contributes to assessment reports of the Intergovernmental Panel on Climate Change (IPCC). [1] IMBIE has led to improved confidence in the measurement of ice sheet mass balance and the associated global sea-level contribution. [2] [3] [4] The improvements were achieved through combination of ice sheet imbalance estimates developed from the independent satellite techniques of altimetry, gravimetry and the input-output method. Going forwards, IMBIE provides a framework for assessing ice sheet mass balance, and has an explicit aim to widen participation to enable the entire scientific community to become involved.

Contents

Results

IMBIE 2012

The IMBIE project produced its first estimate of ice sheet mass balance in 2012 as a direct contribution to the fifth assessment report of the Intergovernmental Panel on Climate Change. [2] IMBIE 2012 included an international team of 47 scientists based in 26 separate institutions, and was co-led by Andrew Shepherd and Erik Ivins. Over the course of the 19-year survey (1992 – 2011), the average rates of mass balance of the Antarctic and Greenland ice sheets were estimated to be -71 ± 53 and -152 ± 49 Gt yr−1, respectively, and the total ice loss equated to a global rise in sea level of 11.1 ± 3.8 mm. [2] Examining the ice sheet regions individually showed that the Greenland, West Antarctic and Antarctic Peninsula ice sheets all lost mass between 1992 and 2011, whilst the East Antarctic ice sheet had undergone a slight snowfall-driven growth. [2] The Greenland ice sheet the largest mass and accounted for about two-thirds of the combined ice sheet loss over the study period. In Antarctica, the largest mass losses have occurred in the West Antarctic Ice Sheet. However, despite occupying just 4% of the total ice sheet area, the Antarctic Peninsula has accounted for around 25% of the Antarctic mass losses. [2]

IMBIE 2018 (Antarctica)

In 2018 the IMBIE project produced an updated assessment of ice loss in Antarctica, combining 24 satellite surveys produced by 84 scientists from 44 international organisations. [3] In this assessment, the IMBIE project reported that between 1992 and 2017 Antarctica lost 2720 ± 1390 billion tonnes of ice, equivalent to an increase in global sea levels by 7.6 ± 3.9 mm. [3] Prior to 2012, Antarctica lost ice at a steady rate of 76 billion tonnes per year – a 0.2 mm per year contribution to sea level rise. However, since then there has been a sharp, threefold increase - between 2012 and 2017 Antarctica lost 219 billion tonnes of ice per year, a 0.6 mm per year sea level contribution. [3] Almost all of the ice lost from Antarctica has been triggered by warming oceans melting their outlet glaciers, which causes them to speed up. [3] Comparison to sea level rise projections provided in the fifth assessment report of the Intergovernmental Panel on Climate Change [5] revealed that Antarctic ice losses are tracking the worst-case climate warming scenarios, which could result in an extra 10 cm of sea level rise by 2100. [6]

IMBIE 2020 (Greenland)

In 2020 the IMBIE project produced an updated assessment of ice loss in Greenland, combining 26 satellite surveys produced by 96 scientists from 50 international organisations. [4] The findings show that Greenland has lost 3902 ± 342 billion tonnes of ice since 1992 – enough to push global sea levels up by 10.8 ± 0.9 millimetres. [4] The rate of ice loss has risen from 34 billion tonnes per year in the 1990s to 234 billion tonnes per year in the last decade – a seven-fold increase within three decades. [4] The team also used regional climate models to show that half of the ice losses were due to surface melting as air temperatures have risen. The other half has been due to increased glacier flow, triggered by rising ocean temperatures. Ice losses peaked at 345 billion tonnes per year in 2011 – ten times the rate of the 1990s - during a period of intense surface melting.  Although the rate of ice loss dropped to an average 206 billion tonnes per year since then, this remains seven times higher than ice losses in the 1990s and does not include all of 2019, which could set a new high due to widespread summer melting. [7] Comparison to sea level rise projections provided in the fifth assessment report of the Intergovernmental Panel on Climate Change [5] revealed that Greenland ice losses are also tracking the worst-case climate warming scenarios, which could result in an extra 7 cm of sea level rise by 2100. [4]

Combining both ice sheets, the rate of ice loss has risen by a factor six in just three decades, up from 81 billion tonnes per year in the 1990s to 475 billion tonnes per year in the 2010s. [3] [4] This means that the polar ice sheets are now responsible for a third of all sea level rise. [8]

See also

Related Research Articles

<span class="mw-page-title-main">Cryosphere</span> Earths surface where water is frozen

The cryosphere is an umbrella term for those portions of Earth's surface where water is in solid form. This includes sea ice, ice on lakes or rivers, snow, glaciers, ice caps, ice sheets, and frozen ground. Thus, there is a overlap with the hydrosphere. The cryosphere is an integral part of the global climate system. It also has important feedbacks on the climate system. These feedbacks come from the cryosphere's influence on surface energy and moisture fluxes, clouds, the water cycle, atmospheric and oceanic circulation.

<span class="mw-page-title-main">Climate of Antarctica</span>

The climate of Antarctica is the coldest on Earth. The continent is also extremely dry, averaging 166 mm (6.5 in) of precipitation per year. Snow rarely melts on most parts of the continent, and, after being compressed, becomes the glacier ice that makes up the ice sheet. Weather fronts rarely penetrate far into the continent, because of the katabatic winds. Most of Antarctica has an ice-cap climate with extremely cold and dry weather.

<span class="mw-page-title-main">Ice shelf</span> Large platform of glacial ice

An ice shelf is a large platform of glacial ice floating on the ocean, fed by one or multiple tributary glaciers. Ice shelves form along coastlines where the ice thickness is insufficient to displace the more dense surrounding ocean water. The boundary between the ice shelf (floating) and grounded ice is referred to as the grounding line; the boundary between the ice shelf and the open ocean is the ice front or calving front.

<span class="mw-page-title-main">Ice sheet</span> Large mass of glacial tulips

In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than 50,000 km2 (19,000 sq mi). The only current ice sheets are the Antarctic ice sheet and the Greenland ice sheet. Ice sheets are bigger than ice shelves or alpine glaciers. Masses of ice covering less than 50,000 km2 are termed an ice cap. An ice cap will typically feed a series of glaciers around its periphery.

<span class="mw-page-title-main">West Antarctic Ice Sheet</span> Segment of Antarctic ice sheet

The West Antarctic Ice Sheet (WAIS) is the segment of the continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere. It is classified as a marine-based ice sheet, meaning that its bed lies well below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf, the Ronne Ice Shelf, and outlet glaciers that drain into the Amundsen Sea.

<span class="mw-page-title-main">Antarctic ice sheet</span> Earths southern polar ice cap

The Antarctic ice sheet is a continental glacier covering 98% of the Antarctic continent, with an area of 14 million square kilometres and an average thickness of over 2 kilometres (1.2 mi). It is the largest of Earth's two current ice sheets, containing 26.5 million cubic kilometres of ice, which is equivalent to 61% of all fresh water on Earth. Its surface is nearly continuous, and the only ice-free areas on the continent are the dry valleys, nunataks of the Antarctic mountain ranges, and sparse coastal bedrock. However, it is often subdivided into East Antarctic ice sheet (EAIS), West Antarctic ice sheet (WAIS), and Antarctic Peninsula (AP), due to the large differences in topography, ice flow, and glacier mass balance between the three regions.

<span class="mw-page-title-main">Greenland ice sheet</span> Vast body of ice in Greenland, Northern Hemisphere

The Greenland ice sheet is an ice sheet which forms the second largest body of ice in the world. It is an average of 1.67 km (1.0 mi) thick, and over 3 km (1.9 mi) thick at its maximum. It is almost 2,900 kilometres (1,800 mi) long in a north–south direction, with a maximum width of 1,100 kilometres (680 mi) at a latitude of 77°N, near its northern edge. The ice sheet covers 1,710,000 square kilometres (660,000 sq mi), around 80% of the surface of Greenland, or about 12% of the area of the Antarctic ice sheet. The term 'Greenland ice sheet' is often shortened to GIS or GrIS in scientific literature.

<span class="mw-page-title-main">Pine Island Glacier</span> Large ice stream, fastest melting glacier in Antarctica

Pine Island Glacier (PIG) is a large ice stream, and the fastest melting glacier in Antarctica, responsible for about 25% of Antarctica's ice loss. The glacier ice streams flow west-northwest along the south side of the Hudson Mountains into Pine Island Bay, Amundsen Sea, Antarctica. It was mapped by the United States Geological Survey (USGS) from surveys and United States Navy (USN) air photos, 1960–66, and named by the Advisory Committee on Antarctic Names (US-ACAN) in association with Pine Island Bay.

<span class="mw-page-title-main">Thwaites Glacier</span> Antarctic glacier

Thwaites Glacier is an unusually broad and vast Antarctic glacier located east of Mount Murphy, on the Walgreen Coast of Marie Byrd Land. It was initially sighted by polar researchers in 1940, mapped in 1959–1966 and officially named in 1967, after the late American glaciologist Fredrik T. Thwaites. The glacier flows into Pine Island Bay, part of the Amundsen Sea, at surface speeds which exceed 2 kilometres (1.2 mi) per year near its grounding line. Its fastest-flowing grounded ice is centered between 50 and 100 kilometres east of Mount Murphy. Like many other parts of the cryosphere, it has been adversely affected by climate change, and provides one of the more notable examples of the retreat of glaciers since 1850.

<span class="mw-page-title-main">Ice stream</span> A region of fast-moving ice within an ice sheet

An ice stream is a region of fast-moving ice within an ice sheet. It is a type of glacier, a body of ice that moves under its own weight. They can move upwards of 1,000 metres (3,300 ft) a year, and can be up to 50 kilometres (31 mi) in width, and hundreds of kilometers in length. They tend to be about 2 km (1.2 mi) deep at the thickest, and constitute the majority of the ice that leaves the sheet. In Antarctica, the ice streams account for approximately 90% of the sheet's mass loss per year, and approximately 50% of the mass loss in Greenland.

<span class="mw-page-title-main">Retreat of glaciers since 1850</span> Recent shrinking of glaciers due to global warming

The retreat of glaciers since 1850 is a well-documented effect of climate change. The retreat of mountain glaciers provide evidence for the rise in global temperatures since the late 19th century. Examples include mountain glaciers in western North America, Asia, the Alps in central Europe, and tropical and subtropical regions of South America and Africa. Since glacial mass is affected by long-term climatic changes, e.g. precipitation, mean temperature, and cloud cover, glacial mass changes are one of the most sensitive indicators of climate change. The retreat of glaciers is also a major reason for sea level rise. Excluding peripheral glaciers of ice sheets, the total cumulated global glacial losses over the 26 years from 1993 to 2018 were likely 5500 gigatons, or 210 gigatons per year.

<span class="mw-page-title-main">Climate change in the Arctic</span> Impacts of climate change on the Arctic

Due to climate change in the Arctic, this polar region is expected to become "profoundly different" by 2050. The speed of change is "among the highest in the world", with the rate of warming being 3-4 times faster than the global average. This warming has already resulted in the profound Arctic sea ice decline, the accelerating melting of the Greenland ice sheet and the thawing of the permafrost landscape. These ongoing transformations are expected to be irreversible for centuries or even millennia.

<span class="mw-page-title-main">East Antarctic Ice Sheet</span> Segment of the continental ice sheet that covers East Antarctica

The East Antarctic Ice Sheet (EAIS) lies between 45° west and 168° east longitudinally. It was first formed around 34 million years ago, and it is the largest ice sheet on the entire planet, with far greater volume than the Greenland ice sheet or the West Antarctic Ice Sheet (WAIS), from which it is separated by the Transantarctic Mountains. The ice sheet is around 2.2 km (1.4 mi) thick on average and is 4,897 m (16,066 ft) at its thickest point. It is also home to the geographic South Pole, South Magnetic Pole and the Amundsen–Scott South Pole Station.

The Centre for Polar Observation & Modelling (CPOM) is a Natural Environment Research Council (NERC) Centre of Excellence that studies processes in the Earth's polar environments. CPOM conducts research on sea ice, land ice, and ice sheets using satellite observations and numerical models.

<span class="mw-page-title-main">Sea level rise</span> Rise in sea levels due to climate change

Between 1901 and 2018, the average sea level rose by 15–25 cm (6–10 in), with an increase of 2.3 mm (0.091 in) per year since the 1970s. This was faster than the sea level had ever risen over at least the past 3,000 years. The rate accelerated to 4.62 mm (0.182 in)/yr for the decade 2013–2022. Climate change due to human activities is the main cause. Between 1993 and 2018, melting ice sheets and glaciers accounted for 44% of sea level rise, with another 42% resulting from thermal expansion of water.

<span class="mw-page-title-main">Eric Rignot</span> American scientist

Eric J. Rignot is the Donald Bren, Distinguished and Chancellor Professor of Earth system science at the University of California, Irvine, and a Senior Research Scientist for the Radar Science and Engineering Section at NASA's Jet Propulsion Laboratory. He studies the interaction of the polar ice sheets in Greenland and Antarctica with global climate using a combination of satellite remote sensing, airborne remote sensing, understanding of physical processes controlling glacier flow and ice melt in the ocean, field methods, and climate modeling. He was elected at the National Academy of Sciences in 2018.

<span class="mw-page-title-main">Ice2sea</span>

Ice2sea was a program of scientific research funded by the European Union's Framework 7 Programme to study the effects of climate change on glaciation and the melting of ice caps and glaciers on sea level. The ice2sea project, a collaborative of 24 research institutions, which was headed by Prof David Vaughan, aimed to reduce the uncertainty in sea-level projections which are of great economic and social importance to European, especially as large areas of coastal Europe are below or less than a metre above sea level.

<span class="mw-page-title-main">Climate change in Antarctica</span> Impacts of climate change on Antarctica

Climate change caused by greenhouse gas emissions from human activities occurs everywhere on Earth, and while Antarctica is less vulnerable to it than any other continent, climate change in Antarctica has been observed. Since 1959, there has been an average temperature increase of >0.05 °C/decade since 1957 across the continent, although it had been uneven. West Antarctica warmed by over 0.1 °C/decade from the 1950s to the 2000s, and the exposed Antarctic Peninsula has warmed by 3 °C (5.4 °F) since the mid-20th century. The colder, stabler East Antarctica had been experiencing cooling until the 2000s. Around Antarctica, the Southern Ocean has absorbed more oceanic heat than any other ocean, and has seen strong warming at depths below 2,000 m (6,600 ft). Around the West Antarctic, the ocean has warmed by 1 °C (1.8 °F) since 1955.

<span class="mw-page-title-main">Past sea level</span> Sea level variations over geological time scales

Global or eustatic sea level has fluctuated significantly over Earth's history. The main factors affecting sea level are the amount and volume of available water and the shape and volume of the ocean basins. The primary influences on water volume are the temperature of the seawater, which affects density, and the amounts of water retained in other reservoirs like rivers, aquifers, lakes, glaciers, polar ice caps and sea ice. Over geological timescales, changes in the shape of the oceanic basins and in land/sea distribution affect sea level. In addition to eustatic changes, local changes in sea level are caused by the earth's crust uplift and subsidence.

Isabella Velicogna is a geoscientist known for her work using gravity measurements from space to study changes in the polar ice sheets and water storage on Earth.

References

  1. ↑ "imbie.org" . Retrieved March 17, 2020.
  2. 1 2 3 4 5 Shepherd, A.; Ivins, E. R.; A, G.; Barletta, V. R.; Bentley, M. J.; Bettadpur, S.; Briggs, K. H.; Bromwich, D. H.; Forsberg, R.; Galin, N.; Horwath, M. (November 30, 2012). "A Reconciled Estimate of Ice-Sheet Mass Balance". Science. 338 (6111): 1183–1189. Bibcode:2012Sci...338.1183S. doi:10.1126/science.1228102. hdl: 2060/20140006608 . ISSN   0036-8075. PMID   23197528. S2CID   32653236.
  3. 1 2 3 4 5 6 Shepherd, Andrew; Ivins, Erik; Rignot, Eric; Smith, Ben; van den Broeke, Michiel; Velicogna, Isabella; Whitehouse, Pippa; Briggs, Kate; Joughin, Ian; Krinner, Gerhard; Nowicki, Sophie (June 2018). "Mass balance of the Antarctic Ice Sheet from 1992 to 2017". Nature. 558 (7709): 219–222. Bibcode:2018Natur.558..219I. doi:10.1038/s41586-018-0179-y. hdl:2268/225208. ISSN   1476-4687. PMID   29899482. S2CID   49188002. Archived from the original on July 8, 2018. Alt URL
  4. 1 2 3 4 5 6 Shepherd, Andrew; Ivins, Erik; Rignot, Eric; Smith, Ben; van den Broeke, Michiel; Velicogna, Isabella; Whitehouse, Pippa; Briggs, Kate; Joughin, Ian; Krinner, Gerhard; Nowicki, Sophie (March 2020). "Mass balance of the Greenland Ice Sheet from 1992 to 2018". Nature. 579 (7798): 233–239. doi:10.1038/s41586-019-1855-2. hdl: 11585/771651 . ISSN   1476-4687. PMID   31822019. S2CID   209316760. Archived from the original on March 27, 2020. Alt URL
  5. 1 2 Intergovernmental Panel on Climate Change, ed. (2014), "Sea Level Change", Climate Change 2013 - The Physical Science Basis, Cambridge University Press, pp. 1137–1216, doi:10.1017/cbo9781107415324.026, ISBN   978-1-107-41532-4 , retrieved March 17, 2020
  6. ↑ Slater, Thomas; Shepherd, Andrew (December 2018). "Antarctic ice losses tracking high". Nature Climate Change. 8 (12): 1025–1026. Bibcode:2018NatCC...8.1025S. doi:10.1038/s41558-018-0284-9. ISSN   1758-6798. S2CID   91480834.
  7. ↑ "Guest post: How the Greenland ice sheet fared in 2019". Carbon Brief. September 6, 2019. Retrieved March 17, 2020.
  8. ↑ Change, NASA Global Climate. "Sea Level | NASA Global Climate Change". Climate Change: Vital Signs of the Planet. Retrieved March 17, 2020.

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