Polar ice sheet melting in past decade is worst in recorded history

In recent years, the polar ice sheets have been suffering from increased melting rates. The worst seven years on record occurring within the past decade. According to a new study published in the journal Earth System Science Data, 2019 was the most devastating year for ice sheet loss, driven primarily by an Arctic summer heatwave. 

Researchers from the Ice Sheet Mass Balance Intercomparison Exercise (IMBIE) have combined data from 50 satellite surveys of Antarctica and Greenland taken between 1992 and 2020. Their findings indicate that the melting polar ice sheets now account for a quarter of all sea level rise. This represents a staggering fivefold increase since the 1990s.

NASA and the European Space Agency (ESA) awarded funding to the international team of researchers known as IMBIE in 2011 to compile a satellite record of polar ice sheet melting. Leading organizations, including the Intergovernmental Panel on Climate Change (IPCC), have widely used the team’s data since its release.

The latest assessment by the IMBIE team, led by Northumbria University‘s Centre for Polar Observations and Modelling, has combined the results of the 50 satellite surveys to determine the rate of ice melting in Antarctica and Greenland.

What researchers learned from the study

The study discovered that between 1992 and 2020, Earth’s polar ice sheets lost a staggering 7,560 billion tons of ice. This amount is equivalent to an ice cube measuring 20 kilometers in height. Throughout the entire satellite record, the polar ice sheets have experienced ice loss every year. The seven highest-melting years all occurring in the past decade.

The 2019 record-breaking ice loss is attributed to a summer heatwave in the Arctic. This led to a peak loss of 444 billion tons of ice from Greenland. In the same year, Antarctica lost 168 billion tons of ice, marking the sixth highest loss on record. 

This significant ice loss was due to the continued acceleration of glaciers in West Antarctica. Record melting on the Antarctic Peninsula also contributed. Meanwhile, the East Antarctic Ice Sheet has remained relatively stable, maintaining a state of balance throughout the satellite era.

The melting of polar ice sheets has led to a 21 mm rise in global sea levels since 1992. Almost two-thirds (13.5 mm) originating from Greenland and one-third (7.4 mm) from Antarctica. In the early 1990s, ice sheet melting contributed only 5.6% to sea level rise. However, this figure has increased fivefold, now accounting for over a quarter (25.6%) of all sea level rise. 

The Intergovernmental Panel on Climate Change (IPCC) predicts that if the ice sheets continue to lose mass at the current rate, they will contribute between 148 and 272 mm to global mean sea levels by the end of the century.

New method to continuously update ice sheet mass

Professor Andrew Shepherd, Head of the Department of Geography and Environmental Sciences at Northumbria University and founder of the Ice Sheet Mass Balance Intercomparison Exercise (IMBIE), stated, “After a decade of work we are finally at the stage where we can continuously update our assessments of ice sheet mass balance as there are enough satellites in space monitoring them, which means that people can make use of our findings immediately.”

Dr. Inès Otosaka from the University of Leeds, who led the study, emphasized the importance of continuous monitoring: “Ice losses from Greenland and Antarctica have rapidly increased over the satellite record and are now a major contributor to sea level rise. Continuously monitoring the ice sheets is critical to predict their future behavior in a warming world and adapt for the associated risks that coastal communities around the world will face.”

The IMBIE team has produced three assessments of ice loss thus far, thanks to the ongoing collaboration between space agencies and the scientific community. The first and second assessments were published in 2012 and 2018/19. 

In recent years, the European Space Agency (ESA) and NASA have launched new satellite missions. These missions are specifically designed to monitor polar regions. The IMBIE project has capitalized on these developments to provide more frequent updates. This enables annual monitoring of polar ice sheet losses for the first time.

Assessing ice sheets from space

The third assessment, funded by ESA and NASA, involved 68 polar scientists from 41 international organizations using measurements from 17 satellite missions. It also included data from the GRACE-FO gravity mission for the first time. 

This latest assessment ensures that ice loss records from Antarctica and Greenland are analyzed using the same methods and cover the same time period. The assessment will now be updated annually to provide the scientific community with the most recent estimates of polar ice losses.

Dr. Diego Fernandez, Head of Research and Development at ESA, remarked, “This is another milestone in the IMBIE initiative and represents an example of how scientists can coordinate efforts to assess the evolution of ice sheets from space, offering unique and timely information on the magnitude and onset of changes.”

He added, “The new annual assessments represent a step forward in the way IMBIE will help to monitor these critical regions, where variations have reached a scale where abrupt changes can no longer be excluded.”

Consequences of ice sheet melting

As global heating continues to impact the polar ice sheets, sea levels are rising. This is causing increased coastal flooding across the planet. The reliable measurement of ice losses from Greenland and Antarctica is now possible thanks to advances in satellite technology. This enables researchers to track changes in ice sheet volume, gravitational pull, or ice flow. 

The ongoing research by the IMBIE team plays a crucial role in understanding the effects of climate change on our polar regions and the subsequent consequences for the global environment.

The study, titled “Antarctic and Greenland Ice Sheet mass balance 1992-2020 for IPCC AR6,” has been published in the journal Earth System Science Data. The new dataset is publicly available on the British Antarctic Survey website.

More about polar ice sheets

Polar ice sheets are vast expanses of ice that cover the landmasses of Greenland and Antarctica. These ice sheets are significant features of Earth’s cryosphere, containing approximately 99% of the planet’s freshwater ice. 

The Greenland Ice Sheet covers roughly 1.7 million square kilometers. The Antarctic Ice Sheet is much larger, encompassing around 14 million square kilometers.

The polar ice sheets play a crucial role in regulating Earth’s climate and maintaining the global heat balance. They reflect a considerable amount of solar radiation back into space due to their high albedo, or reflectivity. This process helps to keep the planet cooler than it would be otherwise. Additionally, ice sheets influence global ocean circulation patterns. The cold, dense water formed near the poles sinks and drives the movement of warmer water from the equator.

However, the polar ice sheets are also highly susceptible to the effects of climate change. As global temperatures rise, ice sheets are melting at an accelerated rate. This contributes to sea level rise and poses a threat to coastal communities worldwide. 

The loss of ice mass from Greenland and Antarctica has been increasing over recent decades. The most significant losses occurring in the past ten years.

The melting of polar ice sheets impacts Earth and humanity in several ways:

Sea level rise

As ice sheets melt, the additional water contributes to rising sea levels. This can lead to flooding and erosion in coastal areas, threaten infrastructure, and displace populations.

Changes to ocean circulation

The influx of freshwater from melting ice sheets can disrupt ocean circulation patterns, potentially leading to shifts in climate and weather patterns.

Loss of habitat

Melting ice sheets affect the habitats of many polar species, such as polar bears, seals, and penguins, which depend on sea ice for survival.

Feedback mechanisms

The loss of ice sheets reduces the Earth’s albedo, causing the planet to absorb more solar radiation and further exacerbating global warming.

Impact on global climate

Changes in the ice sheets can have far-reaching effects on the planet’s climate system, influencing weather patterns and the frequency and intensity of extreme weather events.

Understanding the dynamics of polar ice sheets and their response to climate change is crucial for predicting future sea level rise, developing adaptation strategies, and mitigating the impacts of global warming on ecosystems and human societies.

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