Greenland ice sheet faces irreversible melting

Greenland Ice Sheet
Credit: Unsplash/CC0 Public Domain

In a study published this week in The Cryosphere, researchers from the National Centre for Atmospheric Science and University of Reading demonstrate how climate change could lead to irreversible sea level rise as temperatures continue to rise and the Greenland ice sheet continues to decline.


The massive ice sheet faces a point of no return, beyond which it will no longer fully regrow, permanently changing sea levels around the world.

The Greenland ice sheet is seven times the area of the UK, and stores a large amount of the Earth’s frozen water. At current rates of melting, it contributes almost 1mm to sea level per year, and accounts for around a quarter of total sea level rise.

Since 2003, despite seasonal periods of growth, Greenland’s ice sheet has lost three and a half trillion tons of ice.

Rising sea levels are one of the most severe effects of climate change, threatening coastal areas around the world, and putting millions of people who live in low-lying areas at risk. Bangladesh, Florida, and eastern England are among many areas known to be particularly vulnerable.

Under scenarios in which global warming goes beyond 2°C, the Paris Agreement target, we should expect significant ice loss and several meters of global sea level rise to persist for tens of thousands of years, according to the new research. The warmer the climate, the greater the sea-level rise.

In addition, even if temperatures later return to current levels, scientists have shown that the Greenland ice sheet will never fully regrow once it melts beyond a critical point. After that point, sea levels would permanently remain two meters higher than now, regardless of other factors contributing to sea level rise.

This is because the ice sheet is so large that it has a substantial impact on its local climate, and as it declines, Greenland would experience warmer temperatures and less snowfall.

Once the ice-sheet retreats from the Northern part of the island, the area would remain ice-free.

To avoid the irreversible sea level rise the melting would cause, scientists say that climate change must be reversed before the ice sheet has declined to the threshold mass, which would be reached in about 600 years at the highest rate of mass loss within the likely range of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.

Professor Jonathan Gregory, Climate Scientist from the National Centre for Atmospheric Science and University of Reading, said: “Our experiments underline the importance of mitigating global temperature rise. To avoid partially irreversible loss of the ice sheet, climate change must be reversed—not just stabilized—before we reach the critical point where the ice sheet has declined too far.”

To study the ice-sheet, scientists from the National Centre for Atmospheric Science simulated the effects of Greenland ice sheet melting under a range of possible temperature rises, ranging from minimal warming to worst-case scenarios.

Under all future climates like the present or warmer, the ice-sheet declined in size and contributed

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As the Arctic’s Attractions Mount, Greenland Is a Security Black Hole | World News

By Jacob Gronholt-Pedersen

COPENHAGEN (Reuters) – On a windy August afternoon in 2017, Akitsinnguaq Ina Olsen was relaxing in the old harbour of Nuuk, Greenland’s capital, when a Chinese icebreaker sailed unannounced into the Arctic island’s territorial waters.

“I saw it by chance,” Olsen, 50, told Reuters. “My first thought was: ‘They’re already here!’ They’re pretty cheeky, those Chinese.”

She pulled out her phone and took a picture of the 167-meter long Chinese icebreaker Xue Long (Snow Dragon), before it turned around and disappeared.

The Chinese ship was one of a growing number of unexpected arrivals in Arctic waters as shrinking sea ice has fast-tracked a race among global powers for control over resources and waterways. Both China and Russia have been making increasingly assertive moves in the region, and after the U.S. Secretary of State Mike Pompeo last year said now is “America’s moment to stand up as an Arctic nation and for the Arctic’s future,” military activity is stepping up.

Greenland is a semi-autonomous part of the Kingdom of Denmark and Copenhagen runs the island’s defence through its Joint Arctic Command. On several occasions since 2006, foreign vessels have turned up unexpectedly or without the necessary protocols, in waters that NATO-member Denmark aims to defend, Greenland residents and military sources in Denmark and the United States told Reuters.

Copenhagen and its Arctic neighbours have tried in recent decades to keep the region what they call a “low tension” area. But each event underscores new challenges for Denmark and its allies.

The main problem: It’s hard to see what’s going on there.

Greenland, which U.S. President Donald Trump offered unsuccessfully to buy from Copenhagen last year, is largely an ice sheet with a rocky coastline of 44,000 km (27,000 miles) – longer than the earth’s equator. It’s hidden by almost complete darkness in the winter months.

Beneath its rocks and ice are abundant resources of minerals and rare earth metals used in equipment from smartphones to electric vehicles and military jets, as well as uranium and potentially vast resources of oil and natural gas.

Greenland offers more than resources. The island, which is nearer to New York than New York is to Los Angeles, is also a strategic window onto space.

Located at Thule, the United States’ northernmost air base houses the 21st Space Wing’s network of sensors, which provides early missile warning and space surveillance and control. Thule is one of the few places in the world with access to satellites that orbit the poles, completing coverage of the globe which is essential for weather forecasting, search-and-rescue and climate research.

“Historically the Arctic, like space, was characterised as a predominantly peaceful domain,” Secretary of the U.S. Air Force Barbara Barrett said in July when presenting America’s Arctic strategy in the transcript of a webinar hosted by the Atlantic Council think tank.

Several countries are building new icebreakers to increase freight traffic. China, which in 2018 declared itself a “near-Arctic” nation, has said it wants to build infrastructure and

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As the Arctic’s attractions mount, Greenland is a security black hole

By Jacob Gronholt-Pedersen

COPENHAGEN (Reuters) – On a windy August afternoon in 2017, Akitsinnguaq Ina Olsen was relaxing in the old harbour of Nuuk, Greenland’s capital, when a Chinese icebreaker sailed unannounced into the Arctic island’s territorial waters.

“I saw it by chance,” Olsen, 50, told Reuters. “My first thought was: ‘They’re already here!’ They’re pretty cheeky, those Chinese.”

She pulled out her phone and took a picture of the 167-meter long Chinese icebreaker Xue Long (Snow Dragon), before it turned around and disappeared.

The Chinese ship was one of a growing number of unexpected arrivals in Arctic waters as shrinking sea ice has fast-tracked a race among global powers for control over resources and waterways. Both China and Russia have been making increasingly assertive moves in the region, and after the U.S. Secretary of State Mike Pompeo last year said now is “America’s moment to stand up as an Arctic nation and for the Arctic’s future,” military activity is stepping up.

Greenland is a semi-autonomous part of the Kingdom of Denmark and Copenhagen runs the island’s defence through its Joint Arctic Command. On several occasions since 2006, foreign vessels have turned up unexpectedly or without the necessary protocols, in waters that NATO-member Denmark aims to defend, Greenland residents and military sources in Denmark and the United States told Reuters.

Copenhagen and its Arctic neighbours have tried in recent decades to keep the region what they call a “low tension” area. But each event underscores new challenges for Denmark and its allies.

The main problem: It’s hard to see what’s going on there.

Greenland, which U.S. President Donald Trump offered unsuccessfully to buy from Copenhagen last year, is largely an ice sheet with a rocky coastline of 44,000 km (27,000 miles) – longer than the earth’s equator. It’s hidden by almost complete darkness in the winter months.

Beneath its rocks and ice are abundant resources of minerals and rare earth metals used in equipment from smartphones to electric vehicles and military jets, as well as uranium and potentially vast resources of oil and natural gas.

Greenland offers more than resources. The island, which is nearer to New York than New York is to Los Angeles, is also a strategic window onto space.

Located at Thule, the United States’ northernmost air base houses the 21st Space Wing’s network of sensors, which provides early missile warning and space surveillance and control. Thule is one of the few places in the world with access to satellites that orbit the poles, completing coverage of the globe which is essential for weather forecasting, search-and-rescue and climate research.

“Historically the Arctic, like space, was characterised as a predominantly peaceful domain,” Secretary of the U.S. Air Force Barbara Barrett said in July when presenting America’s Arctic strategy in the transcript of a webinar hosted by the Atlantic Council think tank.

“This is changing.”

Several countries are building new icebreakers to increase freight traffic. China, which in 2018 declared itself a “near-Arctic” nation, has said it

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Scientists harness satellites to track algae growth on Greenland ice sheet

Scientists harness satellites to track algae growth on Greenland ice sheet
Algae growing on the surface of the Greenland ice sheet darkens the surface, hastening summer melting. Here, researchers from Columbia University’s Lamont-Doherty Earth Observatory traverse a heavily affected area. Some of the dark material on the surface could also be dust or other debris. Credit: Kevin Krajick/Earth Institute

Scientists know that the brownish-gray algae that darken the Greenland ice sheet in summer cause the ice to melt faster, but only recently have they measured these blooms in the field, and only at few sites. To measure algal blooms across large regions and understand their effects on melting over time, they are now turning to space.


“Scientists go into the field and sample one or two spots where these blooms occur, but we don’t really know how they change over time or over a large region,” said Shujie Wang, lead author of a recent study showing that satellites can be used to track the growth of ice algae over wide areas.

To measure algae growth, Wang and her colleagues borrowed long-standing methodology used by other scientists to measure algae in the oceans, using satellite observations of water color. Marine algae differ from those on ice, but both kinds contain chlorophyll-a, which has a distinct reflected near-infrared radiation signature that satellite sensors can detect.

Mapping glacier algae over space and time can give researchers insights into how algae affect the reflectivity, or albedo, of the ice surface, said Wang, who conducted the research as a postdoctoral scholar at Columbia University’s Lamont-Doherty Earth Observatory. She is now an assistant professor of geography at Penn State University.

“Albedo is crucial for understanding how ice melts and what will happen in the future to the contribution of Greenland to sea level rise,” said Lamont-Doherty research professor Marco Tedesco, who supervised Wang’s work. “Little is known of the effects of algae on this, and the work by Shujie is pioneering in this regard.”

Light-colored snow and ice have a high albedo, meaning that they reflect most incoming solar radiation back to the atmosphere. But when algae accumulate, they darken the surface; this causes it to absorb more radiation, warming the ice and accelerating surface melt.

Scientists harness satellites to track algae growth on Greenland ice sheet
Study coauthor Marco Tedesco (right) measuring the reflectivity of the glacial surface. Such on-the-ground measurements are combined with satellite observations to study algae growth. Credit: Kevin Krajick/Earth Institute

The researchers used data from the Medium Resolution Imaging Spectrometer (MERIS) on the European Space Agency’s Envisat satellite to quantify algal blooms in southwestern Greenland from 2004 to 2011. They compared the data to measurements taken in the field and by NASA’s Moderate Resolution Imaging Spectrometer (MODIS), which measures surface albedo.

They found that chlorophyll-a signatures captured by MERIS matched field data, confirming that researchers can use ocean-color satellite data to measure algal growth and see how it changes over the summer. The same held true for the albedo changes measured by MODIS.

“We came up with a rough estimate that if algae growth doubles, then albedo decreases between 2 percent to 4

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