Greenland Ice Sheet: The Facts

We explain all you need to know about Greenland’s ice sheet, its polar and tundra ecosystems, its geography, topography and bedrock, and the rapid melting of its glaciers, like Kangerlussuaq Glacier, whose ice is disappearing on average seven times faster today than it was in 1991.
Greenland Meltwater Stream
Meltwater stream running off the Greenland ice sheet. Photo: © Sarah Das/WHOI

What’s going to happen to the Greenland ice sheet as global warming intensifies? What are the consequences if it melts? The truth is, no one knows for sure, but the signs are ominous.

Rising temperatures throughout the circumpolar region have caused widespread Arctic fires, emitting huge greenhouse gas emissions in the process, and raising concerns about premature thawing of permafrost in Siberia, Alaska and Canada.

In addition, the warming is responsible for significant reductions in Arctic sea ice, and the question now is – will it affect Greenland’s glaciers and massive ice cap?

For example, in September 2020, according to imagery from Copernicus Data/ESA/Sentinel satellite, a huge chunk of ice roughly 110 square kilometers in size – known as Spalte Glacier – broke off 79N (Nioghalvfjerdsfjorden) the Arctic’s largest remaining ice shelf in north-east Greenland. Spalte’s disintegration, say researchers, is simply the latest evidence of the rapid climate changes occurring in Greenland.

Why is Greenland Important?

Greenland is the most important part of the cryosphere within the Arctic Circle. It is home to one of only two ice sheets in the world – the other being in Antarctica – and its contribution to Earth’s climate system is immeasurable. The polar regions are the coldest places on the planet, and their stores of frozen freshwater have a critical cooling effect on Earth’s temperature, which is becoming even more important as our climate crisis grows.

Planet Earth receives most of its solar heat in the tropics and subtropics because the sun is higher in the sky, which concentrates the incoming solar radiation over a smaller surface area. Over the poles, the sun is lower, the solar energy is spread over a wider area, and temperatures are lower. To remedy this heat differential, the hydrosphere has a network of deep-water currents – the thermohaline circulation – that redistributes cold water from the poles and warm water from the equator. If the Greenland ice sheet melts, the functioning of the thermohaline circulation is likely to be seriously affected, with incalculable knock-on effects around the globe.

In addition, the vast expanse of snow and ice on the Greenland ice sheet helps to cool the Earth by reflecting up to 90 percent of the sun’s rays it receives, back into space. In climate science this is known as the albedo effect.

Unfortunately, albedo is a two-way process. So, if the island’s glaciers shrink, there is less white surface to reflect sunlight back into space, and the island absorbs more solar heat, which further exacerbates the melting. The mechanism is one of the climate feedbacks that amplifies the effects of global warming.

But the most dangerous consequence of ice sheet melt is the sea level rise it might cause. According to data published in the IPCC’s Fifth Assessment Report, the disintegration of the Greenland ice sheet will raise sea levels by more than 7 meters (23 ft). 1

A rise in global sea levels of 23 feet will submerge several major river deltas along with large stretches of coastline, causing enormous damage to crops and agriculture. In addition, hundreds of coastal cities will be submerged, as well as low-lying areas such as Florida and the Netherlands. Millions of people will be made homeless.

Geography

Greenland is the world’s largest non-continental island. It is bordered to the north by the Arctic Ocean, to the south by the North Atlantic, to the east by the Greenland Sea, and to the west by Baffin Bay and the Davis Strait. Its closest neighbor is Canada’s Ellesmere Island, approximately 20 kms (12.5 miles) across the Nares Strait to the northwest. The strait is usually icebound in winter.

The total surface area of Greenland is 2,166,000 sq km (836,000 sq mi) – more than three times the size of Texas – of which 80 percent is ice sheet. Two-thirds of the island is located within the Arctic Circle, and approaches to within 500 miles (800 km) of the North Pole.

Paradoxically, the far north of Greenland (Peary Land), has no ice sheet, because the dryness of the air prevents any snowfall. The coastal strip around the island is mostly ice-free, rocky and barren tundra, with deep fjords on the western and eastern coasts of the island providing spectacular but desolate landscapes. The coastline is dotted with small islands, especially in the east and west.

Most settlements in Greenland are found along the ice-free section of the coastline, with the population being concentrated along the fjords in the south-west, where about one-third of Greenlanders live in Nuuk, the capital city.

Topography of Greenland ice Sheet and Bedrock

Greenland’s surface is mostly ice sheet, which rises from the coastline to the center of the island, attaining its highest point in the East-Central area, where elevations in the Watkins mountains reach 3,200 meters (10,500 ft). In these high-altitude areas, numerous exposed peaks and ridges (nunataks) can be seen jutting up through the ice.

Greenland’s highest mountain is Gunnbjorn Fjeld peaking at 3,700 meters (12,139 ft), although most of the country is less than 1,500 meters (4,900 ft) in elevation. As a result, generally speaking, the ice sheet flows from the centre of the island down to the coast.

The thickness and weight of the ice sheet in the central area of the island has squashed the bedrock underneath to a depth of 300 meters (1,000 ft) below sea level. In contrast, bedrock along the coastal strip rises sharply as overhead ice reduces to nothing.

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Polar and Tundra Ecosystems

Greenland is made up of two biomes: polar biome in the icy interior, and – thanks to the influence of the warm Gulf Stream – tundra biome along the ice-free coastline. In a polar climate, no mean monthly temperature exceeds 0°C (32°F), although on the Greenland ice sheet, the temperature is typically well below freezing throughout the year, with record-highs only slightly above freezing.

In contrast, a tundra climate signifies a climate in which at least one month has an average temperature in excess of freezing (0°C/32°F), but no month has an average temperature more than 10°C (50°F), even in the warmest summer months. These tundra temperatures are too low to sustain trees, although there is a very small forest in the Qinngua Valley, in the far south of Greenland, that is protected by the surrounding mountains from cold, winds travelling from the ice sheet. The hottest ever temperature recorded on the island is 23.2°C at Kangerlussuaq airport on the west coast. The coldest, minus 66°C (minus 86.8°F) at Summit Camp in the heart of the ice cap.

Average annual precipitation ranges from 1,900 mm (75 inches) in the south to about 50 mm (2 inches in the north. Large parts of the island are classified as Arctic desert because of their lack of precipitation. See also: What is the Water Cycle?

The Greenland Ice Sheet

The Greenland ice sheet – the island’s major physical feature – extends across 1.7 million square kilometers (656,000 square miles), roughly 80 percent of the island’s total land area. It has an average thickness of 1,500 meters (5,000 ft), reaching a maximum thickness of about 3,000 meters (10,000 ft). It has a volume of approximately 2.85 million cubic kilometers (680,000 cu mi). 2

The ice sheet is constantly on the move, flowing outwards to the peripheral glaciers that descend to the sea. Greenland’s largest glacier is the Jakobshavn Glacier, which flows at a rate of about 30 meters (100 ft) per day. Unlike the Antarctic ice sheet, the Greenland sheet does not reach the ocean along a broad front anywhere. As a result, it doesn’t produce floating ice shelves when it meets the sea. Indeed, the rocky coast frequently causes large chunks to break off the glaciers and slide into the water as icebergs.

Retreat of Greenland’s Glaciers

In December 2019, at the annual meeting of the American Geophysical Union, scientists presented satellite images dating back to 1985, of about 200 glaciers in Greenland. The images are the first to compare the extent of glacier retreat on the island and the speed at which it is happening. The satellite imagery revealed that Greenland’s glaciers have retreated about 3 miles (5 kilometers) between 1985 and 2018.

What’s more, since 2000, the pace of retreat has accelerated, resulting in the loss of an extra 50 billion metric tons of ice per year. The triggers for the retreat vary according to region. In the southeast of Greenland, for example, it was caused mostly by warming ocean waters that melted the front of the glaciers. 3

Take Kangerlussuaq Glacier, for example, the largest tidewater glacier on the east coast of the Greenland ice sheet. It flows into the Kangerlussuaq Fjord, the second biggest fjord in East Greenland. It drains about 3 percent of the total area of the ice sheet (Bevan et al, 2012), and accounts for 5 percent of ice discharged (Enderlin et al, 2014). In 2016 the glacier retreated further inland than at any time in the preceding 33 years. 4 In 2017, Kangerlussuaq began a new phase of rapid retreat and its ice front now occupies its most inland position since the early 20th-century. 5

How Fast is Greenland’s Ice Sheet Melting?

Between 1992 and 2018, the Greenland ice sheet lost 3.8 trillion tons of ice. That’s the same as emptying the water from 120 million Olympic-size swimming pools into the ocean, every year for 26 years.

This was the headline finding of a new study conducted by scientists from IMBIE (Ice Sheet Mass Balance Inter-Comparison Exercise) supported by NASA and the European Space Agency (ESA). Combining 26 independent satellite datasets to track the effects of global warming on the Greenland ice cap, and its impact on rising sea levels, the study represents the most accurate measurements of ice loss to date.

One statistic from the study serves to illustrate the trend over the past quarter of a century. Since 1991, Greenland’s ice mass loss has accelerated from 25 billion tons per year to a current average of 234 billion tons per year. In other words, Greenland’s ice is disappearing on average seven times faster today, than it was in 1991. And the loss is becoming more rapid. In the last decade, for example, the rate has increased to 254 billion tonnes a year.

The team found that roughly 50 percent of the ice loss is due to surface ice melting in warmer air. The rest is due to factors such as warmer ocean temperatures, iceberg calving and the increased speed of glaciers transporting ice into the ocean.

The study predicts an approximate 7-13 centimeters (3-5 inches) of global sea level rise by 2100, due solely to the melting of the Greenland ice sheet.

This particular finding is in line with the IPCC’s previous worst-case projections of sea level rise. 6

Erik Ivins, second author and lead scientist at NASA’s Jet Propulsion Laboratory in California, emphasized that because the study was based on satellite observations rather than computer-driven climate models, the team has gleaned irrefutable evidence that the planet is on track with one of the most pessimistic sea level rise scenarios.

“As a rule of thumb, for every centimeter rise in global sea level, another six million people are exposed to coastal flooding around the planet,” said Andrew Shepherd, lead author and scientist from the University of Leeds in the United Kingdom. “On current trends, Greenland ice melting will cause as many as 78 million people to be flooded by the end of the century.”

Even Greater Sea Level Rise

According to another study which used data from NASA’s Operation IceBridge airborne campaign, Greenland’s melting ice sheet could generate 80 percent more sea level rise than previously thought if greenhouse gas emissions continue at their present rate. The study revealed that over the next 200 years, the Greenland ice sheet alone could contribute up to 160 centimeters (63 inches – 5.25 ft) of sea level rise, compared to earlier forecasts of up to 89 centimeters (35 inches). 7

Latest News of Ice Loss from Greenland’s Ice Sheet

In 2019, melting on the Greenland ice sheet (that is, total melt-day extent) was the seventh-highest since 1978, behind 2012, 2010, 2016, 2002, 2007, and 2011. Since 2000, the ice sheet has experienced a general increase in melting, with melt-day area for 2019 totalling 28.3 million square kilometers (10.9m sq miles) for the season. Melting occurred over 90 percent of the island (including much of the high-altitude areas) on at least one day, and was especially noticeable along the northern edge of the sheet, where melting occurred for an additional 35 days compared to the 1981 to 2010 average.

Significantly, the melting even occurred at Summit Station, a research camp nearly 2 miles high at the center of the greenland ice cap, where temperatures rose above freezing on two days in 2019 for more than 16 hours. Up to this point in time, the station temperature exceeded zero for only 6.5 hours in 2012, once in 1889 and in the Middle Ages.

Despite having only the 7th-highest number of melt days, climate models indicate that the ice sheet suffered an ice loss of more than 300 billion metric tons for the year: almost the same as the record-breaking melt year of 2012. 8

Conclusion

As climate change intensifies, the Greenland ice sheet is losing ice at a rapid rate. Unless the burning of fossil fuels is rapidly curtailed and greenhouse gases reduced, this ice melt is predicted to cause 7-13 centimeters of sea level rise by 2100, flooding tens of millions of people in the process. The fact that Greenland contains no more than a tenth of the ice locked up in the Antarctic ice sheet, is an indication of how high sea levels could rise unless climate change mitigation becomes a serious priority.

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References

  1. Observations: Cryosphere. Climate Change 2013: The Physical Science Basis.” David Vaughan. []
  2. IPCC Third Assessment Report (2003) []
  3. Shrinking of Greenland’s glaciers began accelerating in 2000, research finds.” []
  4. Warming of SE Greenland shelf waters in 2016 primes large glacier for runaway retreat“. Bevan, S. L., et al; The Cryosphere Discuss. []
  5. Exceptional Retreat of Kangerlussuaq Glacier, East Greenland, Between 2016 and 2018.” Stephen Brough, et al; Front. Earth Sci. 31 May 2019. []
  6. Mass balance of the Greenland Ice Sheet from 1992 to 2018.” Shepherd, A., Ivins, E., Rignot, E. et al. Nature 579, 233–239 (2020). []
  7. Contribution of the Greenland Ice Sheet to sea level over the next millennium.” Andy Aschwanden, et al; Science Advances 19 Jun 2019: Vol. 5, no. 6. []
  8. Large ice loss on the Greenland ice sheet in 2019.[]
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