Glaciers accelerate in the Getz region of West Antarctica

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Glaciers accelerate in the Getz region of West Antarctica

Posted on by Nicola Bortun

Article first published by University of Leeds

Glaciers in West Antarctica are moving more quickly from land into the ocean, contributing to rising global sea levels.

A 25-year record of satellite observations has been used to show widespread increases in ice speed across the Getz sector for the first time, with some ice accelerating into the ocean by nearly 50%.

The new study, led by the University of Leeds, reports that 14 glaciers in the Getz region are thinning and flowing more quickly into the ocean. Between 1994 and 2018, 315 gigatonnes of ice has been lost, adding 0.9 mm to global mean sea level – equivalent to 126 million Olympic swimming pools of water.

The results published today (19/02/2021) in the journal Nature Communications show that, on average, the speed of all 14 glaciers has increased by almost a quarter with three glaciers speeding up by over 44 %.

Copernicus Sentinel-1 imagery of the Western End of the Getz Ice Shelf

“The Getz basin is losing more ice than it gains through snowfall.“
HEATHER SELLEY, GLACIOLGIST, CENTRE FOR POLAR OBSERVATION AND MODELLING

This research will help scientists determine whether glaciers in the region may collapse in the next few decades and how this could affect future global sea-level rise.

Heather Selley, lead author of the study and a glaciologist at the Centre for Polar Observation and Modelling at the University of Leeds, said: “The Getz region of Antarctica is so remote that humans have never set foot on most of this part of the continent. Satellite radar altimetry records have shown substantial thinning of the ice sheet.”

“However, the high rates of increased glacier speed coupled with “ice thinning“ now confirms the Getz basin is in “dynamic imbalance”, meaning that it is losing more ice than it gains through snowfall.”

“Using a combination of observations and modelling, we show highly localised patterns of acceleration. For instance, we observe the greatest change in the central region of Getz, with one glacier flowing 391 m/year faster in 2018 than in 1994. This is a substantial change as it is now flowing at a rate of 669 m/year, a 59% increase in just two and a half decades.”

The research, funded by the Natural Environment Research Council (NERC) and the European Space Agency (ESA), reports how the widely reported thinning and acceleration observed in the neighbouring Amundsen Sea glaciers, now extends over 1,000 km along the West Antarctic coastline into Getz.

Dr Anna Hogg, study co-author and climate researcher in Leeds’ School of Earth and Environment said: “The pattern of glacier acceleration shows the highly localised response to ocean dynamics.

“High-resolution satellite observations from satellites such as ESA’s Sentinel-1, which collects a new image every six-days, means we can measure localized speed changes with ever greater detail.

“Consistent and extensive sampling of both ice speed and ocean temperature are needed to further our understanding of the dynamic ice loss, which now accounts for 98.8 % of the Antarctica’s sea level contribution.”

By examining 25 years of ocean measurements, the research team were able to show complex and annual variations in ocean temperatures. These results suggest that the “dynamic imbalance” is mainly caused by longer-term ocean forcing, where increased heat content in the ocean is interacting with the ice and enhancing melt.

Pierre Dutrieux, study co-author and climate researcher at British Antarctic Survey, said: “We know that warmer ocean waters are eroding many of West Antarctica’s glaciers, and these new observations demonstrate the impact this is having on the Getz region.

“This new data will provide a new perspective of the processes taking place so we can predict future change with more certainty.”

Further information

The research team led by the University of Leeds included colleagues from Swansea University, Colombia University, British Antarctic Survey, ENVEO IT GmbH, Remote Sensing Technology Institute in Germany, University of Denmark, University College London and Korea Polar Research Institute.

The study, “Widespread increase in dynamic imbalance in the Getz region of Antarctica from 1994 to 2018”, is published 23 February 2021 in Nature Communications. DOI: 10.1038/s41467-021-21321-1 

Researchers in this study were supported by various grants. Anna E. Hogg was supported by the NERC DeCAdeS project (NE/T012757/1) and ESA Polar+ Ice Shelves project (ESA-IPL-POE-EF-cb-LE-2019-834). Pierre Dutrieux was supported by NSF awards 1643285, 1644159, and a Columbia University Climate and Life Fellowship. Tae-Wan Kim from the Korea Polar Research Institute, grant KOPRI PE20160.

Getz ice shelf photo credit: Pierre Dutrieux

For further details, contact Ian Rosser in the University of Leeds press office via i.rosser@leeds.ac.uk

CPOM research shows that global ice loss increases are at record rate

Posted on by Nicola Bortun
The rate at which ice is disappearing across the planet is speeding up, according to new CPOM research. The findings also reveal that the Earth lost 28 trillion tonnes of ice between 1994 and 2017 equivalent to a sheet of ice 100 metres thick covering the whole of the UK.
The research is the first of its kind to carry out a survey of global ice loss using satellite data.

Article first published by University of Leeds

Scientists led by CPOM found that the rate of ice loss from the Earth has increased markedly within the past three decades, from 0.8 trillion tonnes per year in the 1990s to 1.3 trillion tonnes per year by 2017.

Ice melt across the globe raises sea levels, increases the risk of flooding to coastal communities, and threatens to wipe out natural habitats which wildlife depend on.

“The ice sheets are now following the worst-case climate warming scenarios.“

DR THOMAS SLATER, CENTRE FOR POLAR OBSERVATION AND MODELLING

The findings of the research team, which includes the University of Edinburgh, University College London and data science specialists Earthwave, are published in European Geosciences Union’s journal The Cryosphere.

Funded by the UK Natural Environment Research Council, the research shows that overall, there has been a 65% increase in the rate of ice loss over the 23-year survey. This has been mainly driven by steep rises in losses from the polar ice sheets in Antarctica and Greenland.

Lead author Dr Thomas Slater, a Research Fellow at Leeds’ Centre for Polar Observation and Modelling, said: “Although every region we studied lost ice, losses from the Antarctic and Greenland ice sheets have accelerated the most.”

“The ice sheets are now following the worst-case climate warming scenarios set out by the Intergovernmental Panel on Climate Change. Sea-level rise on this scale will have very serious impacts on coastal communities this century.”

Dr Slater said the study was the first of its kind to examine all the ice that is disappearing on Earth using satellite observations.

He added: “Over the past three decades there’s been a huge international effort to understand what’s happening to individual components in Earth’s ice system, revolutionised by satellites which allow us to routinely monitor the vast and inhospitable regions where ice can be found.

“Our study is the first to combine these efforts and look at all the ice that is being lost from the entire planet.”

The survey covers 215,000 mountain glaciers spread around the planet, the polar ice sheets in Greenland and Antarctica, the ice shelves floating around Antarctica, and sea ice drifting in the Arctic and Southern Oceans.

Rising atmospheric temperatures have been the main driver of the decline in Arctic sea ice and mountain glaciers across the globe, while rising ocean temperatures have increased the melting of the Antarctic ice sheet. For the Greenland ice sheet and Antarctic ice shelves, ice losses have been triggered by a combination of rising ocean and atmospheric temperatures.

Global ice loss increases at record rate

During the survey period, every category lost ice, but the biggest losses were from Arctic Sea ice (7.6 trillion tonnes) and Antarctic ice shelves (6.5 trillion tonnes), both of which float on the polar oceans.

Dr Isobel Lawrence, a Research Fellow at Leeds’ Centre for Polar Observation and Modelling, said: “Sea ice loss doesn’t contribute directly to sea level rise but it does have an indirect influence. One of the key roles of Arctic sea ice is to reflect solar radiation back into space which helps keep the Arctic cool.

“As the sea ice shrinks, more solar energy is being absorbed by the oceans and atmosphere, causing the Arctic to warm faster than anywhere else on the planet.

“Not only is this speeding up sea ice melt, it’s also exacerbating the melting of glaciers and ice sheets which causes sea levels to rise.”

Half of all losses were from ice on land including 6.1 trillion tonnes from mountain glaciers, 3.8 trillion tonnes from the Greenland ice sheet, and 2.5 trillion tonnes from the Antarctic ice sheet. These losses have raised global sea levels by 35 millimetres.

It is estimated that for every centimetre of sea level rise, approximately a million people are in danger of being displaced from low-lying homelands.

Despite storing only 1% of the Earth’s total ice volume, glaciers have contributed to almost a quarter of the global ice losses over the study period, with all glacier regions around the world losing ice.

Report co-author and PhD researcher Inès Otosaka, also from Leeds’ Centre for Polar Observation and Modelling, said: “As well as contributing to global mean sea level rise, mountain glaciers are also critical as a freshwater resource for local communities.

“The retreat of glaciers around the world is therefore of crucial importance at both local and global scales.”

Just over half (58%) of the ice loss was from the northern hemisphere, and the remainder (42%) was from the southern hemisphere.

Further information

Earth’s ice imbalance is published in the European Geosciences Union’s journal The Cryosphere on 25 January 2021. Its DOI is 10.5194/tc-15-233-2021.

Image credits: CPOM; Ian Joughin channel created by the flow of melted ice in Greenland.

For further details or to arrange interviews, contact Ian Rosser in the University of Leeds press office via i.rosser@leeds.ac.uk 

New place names to commemorate the 200th Anniversary of the discovery of Antarctica

Posted on by Nicola Bortun

The Government of the British Antarctic Territory has announced 28 new place names in the Territory today to commemorate the 200th Anniversary of the discovery of Antarctica.

All of the names on the list were chosen to honour people who have made an exceptional contribution to furthering the understanding, protection and management of Antarctica over the last fifty years, and whose achievements warrant highlighting alongside those of the early explorers.

Included in the list of honours were two scientists, Professor Seymour Laxon and Dr Katherine Giles, who were integral to the development of the Centre for Polar Observation and Modelling and whose research still underpins much of our work today. Sadly, Professor Laxon and Dr Giles both died within three months of each other in 2013.

Professor Seymour Laxon (1963-2013)

Laxon BayBay about 10 km wide and 3 km deep between Palosuo Islands and the west side of Renaud Island, Biscoe Islands.

Named for Professor Seymour Laxon, Director, Centre for Polar Observation and Modelling at University College London.

Professor Laxon was at the heart of all the achievements and successes of the Centre for Polar Observation and Modelling for two decades. His scientific breakthrough was to distinguish the ice surface from the water surface in satellite radar altimeter measurements of ice-covered oceans. This led to the first detailed map of the Arctic gravity field, revealing new tectonic features beneath the seafloor, and water circulation beneath the ice. His work also provided evidence that led to the development of the European Space Agency’s CryoSat mission.

Professor Laxon was an empirical scientist, and the integrity with which he treated his data was matched by the integrity and generosity with which he treated his colleagues and students, many of whom are now furthering our understanding of the Arctic through their own careers in the UK and overseas.

More detail about Professor Laxon’s life and work can be found in his obituary in The Guardian (February 2013).

Dr Katherine Giles (1978-2013)

Giles BayBay about 4 km wide and 3 km deep between Weaver Point and Tula Point at the northern end of Renaud Island, Biscoe Islands.

Named for Dr Katharine Giles, Lecturer at University College London, a ground-breaking researcher into sea ice, ocean circulation and wind patterns who worked at University College London.

Dr Giles’s research focussed on sea ice, ocean circulation and wind patterns, and pioneered the use of satellite altimetry to measure the thickness of Arctic and Antarctic sea ice. After it had become clear that sea ice freeboard could be determined from satellite altimetry, Dr Giles performed some of the first ground-based experiments to show how the same observations could be accurately related to sea ice thickness.  This led her to undertake field campaigns to characterise radar penetration into sea ice, both in the Arctic and the Antarctic, and to identify that, in 2007, sea ice thinning accompanied the then record Arctic sea ice minimum extent.

Dr Giles was the first person to appreciate that altimeter observations between sea ice floes were more than just a stepping stone to measuring sea ice thickness: she demonstrated that they could also show how winds affected the newly-exposed Arctic Ocean.

She was also a passionate science communicator. The Dr Katharine Giles science blog prize is awarded by the Association of British Science Writers each year, founded following her tragically early death.

More detail can be found in Dr Giles’s obituary in the Times Higher Education (April 2013).

Renaud Island at the Antarctic Peninsula, 65.6924 South 65.9872 West

Also included in the list of honours is Professor Dame Jane Francis (Director of the British Antarctic Survey):

Francis PeakLocally prominent peak (1136 m), with imposing cliffs on its eastern side, on the horseshoe shaped ridge east of Mount Liotard, Adelaide Island.

Professor Dame Jane Francis is the current and first female Director of the British Antarctic Survey (from 2013), and Chancellor at the University of Leeds (from 2018).

Dame Jane is a leading palaeobotanist and Professor of palaeoclimatology who specialises in the study of fossil plants, especially woods, and their use as tools for climate interpretation and information about past biodiversity in the polar regions. She is the first woman to chair a Working Group of Antarctic Treaty Consultative Meetings. She was awarded the Polar Medal in 2002 for outstanding contribution to British polar research and was appointed Dame Commander of the Order of St Michael and St George (DCMG) for services to polar science and diplomacy.

The full list of new place names can be found here.

More details about place naming and the Antarctic Place Names Committee can be found at: www.apc.antarctica.ac.uk

Ice sheets could add 39 centimetres to sea level by 2100

Posted on by Nicola Bortun

Scientists warn that if greenhouse gas emissions continue apace, Greenland and Antarctica’s ice sheets could together contribute more than 39cm to global sea level rise this century.

From University of Leeds press release, 17th September

The Ice Sheet Model Intercomparison Project (ISMIP6) is an international team, which includes a number of CPOM scientists, making predictions of ice sheet change under future climate scenarios to support the Intergovernmental Panel on Climate Change (IPCC).

ISMIP6 is led by NASA’s Goddard Space Flight Centre in Greenbelt, Maryland and brings together more than 60 ice, ocean and atmosphere scientists, including CPOM Director Andrew Shepherd (University of Leeds), CPOM Land Ice Lead Tony Payne (University of Bristol), CPOM staff researcher Victoria Lee (University of Bristol), and CPOM Associate Investigators Tamsin Edwards (King’s College London) and Isabel Nias (University of Liverpool).

Their latest findings, published this week in a special issue of the journal The Cryosphere, has estimated the impact Earth’s melting ice sheets could have on global sea levels by the end of the century.

The results reinforce projections made by the Intergovernmental Panel on Climate Change (IPCC) in their 2019 Special Report on Oceans and the Cryosphere.

The ISMIP6 team investigated two different scenarios the IPCC has set for future climate to predict sea level rise between 2015 and 2100: one with carbon emissions increasing rapidly and another with lower emissions.

Under the high emissions scenario, ice losses from Greenland cause an additional 9 cm of global sea level rise by 2100, while Antarctica causes an additional 30 cm over the same period.

Under the lower emissions scenario, Greenland’s ice loss would raise global sea level by about 3 cm by 2100, while Antarctic growth would lower sea level by 7.8 cm.

The greatest loss is from West Antarctica, responsible for up to 18 cm of sea level rise by 2100 in the warmest conditions.

The new results from ISMIP6 will inform the IPCC’s Sixth Assessment Report, scheduled for release in 2022.

“Unfortunately, it’s now clear that ice sheet losses have risen rapidly during our lifetime, and that this will continue if we don’t reduce our CO2 emissions.“

PROFESSOR ANDREW SHEPHERD

Professor Shepherd said: “Having three decades of satellite measurements has greatly improved our ability to simulate how Antarctica and Greenland respond to climate change. Unfortunately, it’s now clear that ice sheet losses have risen rapidly during our lifetime, and that this will continue if we don’t reduce our CO2 emissions.

“An extra 39 centimetres of sea level rise will cause huge disruption for our coastal communities, so we should view these predictions as a powerful early warning but now is the time to act.”

“One of the biggest uncertainties when it comes to how much sea level will rise in the future is how much the ice sheets will contribute,” said project leader and ice scientist Sophie Nowicki, now at the University at Buffalo, and formerly at NASA Goddard. “And how much the ice sheets contribute is really dependent on what the climate will do.”

“The strength of ISMIP6 was to bring together most of the ice sheet modelling groups around the world, and then connect with other communities of ocean and atmospheric modelers as well, to better understand what could happen to the ice sheets,” said Heiko Goelzer, a scientist from Utrecht University in the Netherlands, now at NORCE Norwegian Research Centre in Norway. Goelzer led the Greenland ice sheet ISMIP6 effort.

“The Amundsen Sea region in West Antarctica and Wilkes Land in East Antarctica are the two regions most sensitive to warming ocean temperatures and changing currents, and will continue to lose large amounts of ice,” said Helene Seroussi, an ice scientist at NASA’s Jet Propulsion Laboratory in Southern California.

Seroussi led the Antarctic ice sheet modelling in the ISMIP6 effort. “With these new results, we can focus our efforts in the correct direction and know what needs to be worked on to continue improving the projections.”

Further information: 

Top image: Credit: Ian Joughin Icebergs in Disko Bay, Greenland

For additional information contact press officer Anna Harrison a.harrison@leeds.ac.uk 

The earth has lost 28 trillion tonnes of ice in less than 30 years

Posted on by Nicola Bortun

A CPOM-led study, which shows that 28 trillion tonnes of ice have disappeared from the surface of the Earth since 1994 due to greenhouse gas emissions, has captured media and public attention.

CPOM researchers Professor Andy Shepherd, Dr Tom Slater (first author on the paper, and Dr Isobel Lawrence are quoted in a number of articles, including The Guardian:

“To put the losses we’ve already experienced into context, 28 trillion tonnes of ice would cover the entire surface of the UK with a sheet of frozen water that is 100 metres thick,” added group member Tom Slater from Leeds University. “It’s just mind-blowing.“

The research has been translated in to at least 9 different languages, and high-profile attention includes Greta Thunberg, Caroline Lucas and the World Economic Forum.

Past evidence supports complete loss of Arctic sea-ice by 2035

Posted on by Nicola Bortun

A new study, published this week in the journal Nature Climate Change, supports predictions that the Arctic could be free of sea ice by 2035.

High temperatures in the Arctic during the last interglacial “the warm period around 127,000 years ago“ have puzzled scientists for decades. Now the UK Met Office’s Hadley Centre climate model has enabled an international team of researchers to compare Arctic sea ice conditions during the last interglacial with present day.  Their findings are important for improving predictions of future sea ice change.

During spring and early summer, shallow pools of water form on the surface of Arctic sea-ice.  These “melt ponds” are important for how much sunlight is absorbed by the ice and how much is reflected back into space.  The new Hadley Centre model is the UK’s most advanced physical representation of the Earth’s climate and a critical tool for climate research and incorporates sea-ice and melt ponds.

Using the model to look at Arctic sea ice during the last interglacial, the team concludes that the impact of intense springtime sunshine created many melt ponds, which played a crucial role in sea-ice melt.  A simulation of the future using the same model indicates that the Arctic may become sea ice-free by 2035.

Dr David Schroeder, CPOM staff researcher at the University of Reading, who developed and co-led the implementation of the melt pond scheme in the climate model, said: “This shows just how important sea-ice processes like melt ponds are in the Arctic, and why it is crucial that they are incorporated into climate models.”

Professor Danny Feltham, CPOM Sea Ice Lead, and Professor Julienne Stroeve, CPOM Associate Investigator, were also co-authors of the study.

Atmospheric Blocking and Greenland Melt

Posted on by Nicola Bortun

CPOM researchers Victoria Lee and Tony Payne have co-authored, alongside Robin S. Smith (NCAS), an article on Atmospheric Blocking and Greenland Melt for the UK Earth system modelling project (UKESM) July newsletter.

Atmospheric blocking occurs when near-stationary high-pressure systems divert westerly flow for a week or more. It can cause extreme regional weather such as heatwaves in summer and cold spells in winter. This article explores the connection between blocking over Greenland and enhanced surface melting of the ice sheet in UKESM1.ice N96 ORCA1 present-day run.

Mean summer geopotential height at 500 hPa in metres with white contours every 25 m for years 1985, 1991, 2004 and 2011. GBI is calculated inside the region marked by magenta lines. Black contours mark the edge of land:

CPOM researchers contribute to the newly released Copernicus European State of the Climate Report 2019

Posted on by Nicola Bortun

A comprehensive annual climate overview, on which CPOM researchers were co-authors, has been released by the Copernicus Climate Change Service (C3S) containing invaluable insight into the state of our climate in 2019 to help build up a long-term picture of how it is changing. 

Key findings included:

  • 2019 was the warmest year on record for Europe
  • 11 of the 12 warmest years occurred since 2000 in Europe
  • Long-term view shows clear warming trend across the last four decades
  • European Arctic relatively colder than in recent years but summer heatwave causes record surface ice melting in Greenland.

The Greenland Ice Sheet section of the report provides further information: The European State of the Climate 2019, compiled by C3S from a range of data sources with contributions from key players in the field of climate science, offers a complete overview of annual and seasonal conditions across the whole of Europe and the European Arctic which are compared with the long-term average. This gives a clear picture for policymakers, planners, industry sectors, businesses and individuals to help put in place mitigation and adaptation measures against the effect of climate change.

KEY MESSAGES: 

  • In Summer 2019, the Greenland ice sheet experienced record melting.
  • Model estimates indicate that as a result, the surface mass balance anomaly was the lowest on record, at 320 gigatonnes (Gt) below the 1981-2010 average.

During summer 2019, warm air reached the Greenland ice sheet and persistent anticyclonic conditions trapped it there for an extended period. The result was widespread surface melting across the entire ice sheet, with satellite observations showing that 95.8% of the ice sheet surface experienced melting at least once during the summer months. The figure below shows the daily extent of the melt for all of Greenland, with a large peak in late July and early August.

Percentage of the total area of the Greenland ice sheet experiencing melting on a daily basis. The blue line shows melt extent during 2019. The dark grey line shows the mean value for the 1981-2010 reference period. The light grey area shows the range over the 1981-2010 reference period, with the lowest and highest values for each day omitted. Data source: Polar portal Greenland daily surface melt estimate. Credit: DMI Polar Portal. 

The Greenland ice sheet gains mass through snowfall during winter and loses mass through surface melting during late spring and summer (usually from May through to the end of August). The difference between the accumulation and melting of snow and ice is called the surface mass balance. Surface mass balance is calculated annually for 1 September to 31 August, based on models that simulate the different surface processes. It does not take into account ice losses from icebergs calving or glacier ice melting at the margins of the ice sheet due to warm ocean temperatures. Generally, the surface mass balance is positive.

The 2019 surface mass balance was the lowest since the start of the record in 1949, with a negative anomaly of 320 gigatonnes (Gt) per year compared to the 1981-2010 average. Below-average snowfall and an early start to the melting season (mid-April) resulted in the early exposure of bare ice. This further enhanced melting, as bare ice reflects less solar energy than fresh snow, in what is termed melt-albedo feedback.

Between 1992 and 2018, surface mass balance accounted for just over half of the total ice loss (50.3%) in Greenland. However, surface mass balance is highly variable from year to year. While 2019 saw a record low surface mass balance year, the two previous years were above the 1981-2010 average by 80 and 150 Gt, respectively. The remaining ice losses are due to discharge and are measured using satellites; discharge losses have progressively increased from -52 ± 44 Gt/yr for 19921997 to -75 ± 21 Gt/yr for 2012-2017. As the discharge data are not yet available for 2019, it is not possible at this stage to make the full ice loss assessment for 2019.

Read more about how ice sheets are changing in the Ice Sheet indicator.

Carlo Buontempo, Director of the Copernicus Climate change Service (C3S), comments: “It is now more vital than ever before that everyone has access to this information to help us understand the longer-term implications of climate change and what organisations and individuals can do to reduce its effects. One exceptional warm year does not constitute a warming trend, but to have detailed information from our operational service, that covers many different aspects of our climate, we are able to connect the dots to learn more about how it is changing.”

Six-fold increase in polar ice losses since the 1990s

Posted on by Nicola Bortun

Greenland and Antarctica are losing ice faster than in the 1990s and are both tracking the Intergovernmental Panel on Climate Change’s worst-case climate warming scenario.

As a result, this will lead to an extra 17 centimetres of sea level rise by 2100.

A team of 89 polar scientists from 50 international organisations have produced the most complete picture of polar ice sheet loss to date.

The Ice Sheet Mass Balance Intercomparison Exercise (IMBIE) team combined 26 separate surveys to compute changes in the mass of the Greenland and Antarctic ice sheets between 1992 and 2018.

Altogether, data from 11 different satellite missions were used, including measurements of the ice sheets’ changing volume, flow and gravity.

The findings, published in two companion articles in Nature, show that Greenland and Antarctica lost 6.4 trillion tonnes of ice between 1992 and 2017 pushing global sea levels up by 17.8 millimetres. Of the total sea level rise, 10.6 millimetres (60%) was due to Greenland ice losses and 7.2 millimetres (40%) was due to Antarctica.

“If Antarctica and Greenland continue to track the worst-case climate warming scenario, they will cause an extra 17 centimetres of sea level rise by the end of the century.“

PROFESSOR ANDREW SHEPHERD, IMBIE CO-LEADER

The combined 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. This means that the polar ice sheets are now responsible for a third of all sea level rise.

The assessment, led by Professor Andrew Shepherd at the University of Leeds and Dr Erik Ivins at NASA’s Jet Propulsion Laboratory in California, was supported by the European Space Agency (ESA) and the US National Aeronautics and Space Administration (NASA).

In their Fifth Assessment Report, the Intergovernmental Panel on Climate Change (IPCC) predicted that global sea levels will rise 53 centimetres by 2100, and it is estimated that this would put 360 million people at risk of annual coastal flooding.

But the IMBIE Team’s studies shows that ice losses from both Antarctica and Greenland are rising faster than expected, tracking the IPCC’s worst-case (high-end) climate warming scenario.

Professor Shepherd said: “Every centimetre of sea level rise leads to coastal flooding and coastal erosion, disrupting people’s lives around the planet.

“If Antarctica and Greenland continue to track the worst-case climate warming scenario, they will cause an extra 17 centimetres of sea level rise by the end of the century.

“This would mean 400 million people are at risk of annual coastal flooding by 2100.

“These are not unlikely events with small impacts; they are already underway and will be devastating for coastal communities.”

Almost all of the ice lost from Antarctica and half of that lost from Greenland has been triggered by oceans melting their outlet glaciers, which causes them to speed up. The remainder of Greenland’s ice losses are due rising air temperature, which has melted the ice sheet at its surface.

Combined losses from both ice sheets peaked at 552 billion tonnes per year in 2010 and averaged 475 billion tonnes per year for the remainder of the decade. The peak loss coincided with several years of intense surface melting in Greenland, and last summer’s Arctic heatwave means that 2019 should set a new record for polar ice sheet loss. Antarctica and Greenland are now losing ice five and seven times faster than they were in the 1990s, respectively.

“The findings reported by IMBIE demonstrate the fundamental importance of using satellites to monitor the evolution of ice sheets“

JOSEF ASCHBACHER, ESA’S DIRECTOR OF EARTH OBSERVATION PROGRAMMES

Dr Ivins said: “Satellite observations of polar ice are essential for monitoring and predicting how climate change could affect ice losses and sea level rise.

“While computer simulation allows us to make projections from climate change scenarios, the satellite measurements provide prima facie, rather irrefutable, evidence.

“Our project is a great example of the importance of international collaboration to tackle problems that are global in scale.

Guofinna Aoalgeirsdottir, Professor of Glaciology at the University of Iceland and lead author of the Intergovernmental Panel on Climate Change’s sixth assessment report, who was not involved in the study, said:

“The IMBIE Team’s reconciled estimate of Greenland and Antarctic ice loss is timely for the IPCC. Their satellite observations show that both melting and ice discharge from Greenland have increased since observations started.

“The ice caps in Iceland had similar reduction in ice loss in the last two years of their record, but summer 2019 was very warm in this region which resulted in higher mass loss. I would expect a similar increase in Greenland mass loss for 2019.

“It is very important to keep monitoring the big ice sheets to know how much they raise sea level every year.”

ESA’s Director of Earth Observation Programmes, Josef Aschbacher, comments: “The findings reported by IMBIE demonstrate the fundamental importance of using satellites to monitor the evolution of ice sheets, and for evaluating models used to predict the effects of climate change.”

Further information

Image credits: Hamish Pritchard and Professor Andrew Shepherd

Greenland losing ice “faster than expected”

Posted on by Nicola Bortun

Greenland is losing ice faster than in the 1990s and is tracking the Intergovernmental Panel on Climate Change’s high-end climate scenario.

As a result, 40 million more people will be exposed to coastal flooding by 2100.

A team of 89 polar scientists from 50 international organisations have produced the most complete picture of Greenland ice loss to date.

The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) Team combined 26 separate surveys to compute changes in the mass of Greenland’s ice sheet between 1992 and 2018. Altogether, data from 11 different satellite missions were used, including measurements of the ice sheet’s changing volume, flow and gravity.

The findings, published today in Nature, show that Greenland has lost 3.8 trillion tonnes of ice since 1992 – enough to push global sea levels up by 10.6 millimetres.

The rate of ice loss has risen from 33 billion tonnes per year in the 1990s to 254 billion tonnes per year in the last decade – a seven-fold increase within three decades.

“On current trends, Greenland ice melting will cause 100 million people to be flooded each year by the end of the century.”

PROFESSOR ANDREW SHEPHERD, CPOM DIRECTOR

The assessment, led by Professor Andrew Shepherd at the University of Leeds and Dr Erik Ivins at NASA’s Jet Propulsion Laboratory in California, was supported by the European Space Agency (ESA) and the US National Aeronautics and Space Administration (NASA).

In 2013, the Intergovernmental Panel on Climate Change (IPCC) predicted that global sea levels would rise 60 centimetres by 2100, putting 360 million people at risk of annual coastal flooding.

But this new study shows that Greenland’s ice losses are rising faster than expected and are instead tracking the IPCC’s high-end climate warming scenario, which predicts 7 centimetres more.

Professor Shepherd said: “As a rule of thumb, for every centimetre rise in global sea level another six million people are exposed to coastal flooding around the planet.

“On current trends, Greenland ice melting will cause 100 million people to be flooded each year by the end of the century, so 400 million in total due to all sea level rise.

“These are not unlikely events or small impacts; they are happening and will be devastating for coastal communities.”

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 were due to increased glacier flow, triggered by rising ocean temperatures.

Ice losses peaked at 335 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 238 billion tonnes per year since then, this remains seven times higher and does not include all of 2019, which could set a new high due to widespread summer melting.

Dr Ivins said: “Satellite observations of polar ice are essential for monitoring and predicting how climate change could affect ice losses and sea level rise.

“While computer simulation allows us to make projections from climate change scenarios, the satellite measurements provide prima facie, rather irrefutable, evidence.

“Our project is a great example of the importance of international collaboration to tackle problems that are global in scale.”

“IMBIE’s reconciled estimate of Greenland ice loss is timely for the IPCC. Their satellite observations show that both melting and ice discharge from Greenland have increased.”

GUOFINNA AOALGEIRSDOTTIR, UNIVERSITY OF ICELAND

Guofinna Aoalgeirsdottir, Professor of Glaciology at the University of Iceland and lead author of the Intergovernmental Panel on Climate Change’s sixth assessment report, who was not involved in the study, said:

“The IMBIE Team’s reconciled estimate of Greenland ice loss is timely for the IPCC. Their satellite observations show that both melting and ice discharge from Greenland have increased since observations started.

“The ice caps in Iceland had similar reduction in ice loss in the last two years of their record, but this last summer was very warm here and resulted in higher loss. I would expect a similar increase in Greenland mass loss for 2019.

“It is very important to keep monitoring the big ice sheets to know how much they raise sea level every year.”

Further information

Image credits: Ian Joughin

The paper “Mass balance of the Greenland Ice Sheet from 1992-2018” by the IMBIE Team, is published in Nature on 10 December 2019.