Sunday , June 20 2021

Why can we save the Greenland ice sheet | Horizon: the EU research and innovation magazine



Greenland has more than two trillion tons of water locked in a huge blanket of ice that suffocates 80 percent of its land. If that disappeared, it would cause sea levels around the world to increase by an average of seven meters, leaving many shorelines and islands submerged.

And as rising temperatures in the Arctic have led to sea ice covering much of the region's ocean to retreat further, scientists have nervously studied the melting of the Greenland ice sheet to see how it is being affected.

They fear that without the insulating effect of sea ice – along with its ability to reflect summer sunlight – Greenland may suffer accelerated levels of melting in the coming decades. In fact, with global temperatures now warmer by more than 11,000 years, there are concerns that the world has already committed to the melting of Greenland in the coming decades.

Now, surveys that use sophisticated computer models to simulate the relationship between the Arctic and the ice sheet in Greenland suggest that this may not be the case.

Researchers working on the Ice2Ice project have shown that changes in sea ice and the Greenland ice sheet seem to occur quite independently of one another. Sea ice is prone to temperature changes in the layers of water in the ocean, while most of Greenland respond to increases in atmospheric temperature.

A millennium-scale simulation of the Greenland ice sheet and climate change shows that its melting is largely independent of sea ice. Video Credits – DMI, CSC (J. Hokkanen, Visualization)

The discovery indicates that while the Arctic ice seems to be dwindling, the Greenland ice sheet may remain for many centuries. It suggests that efforts to reduce greenhouse gas emissions and limit global temperature rise to less than 2 ° C above pre-industrial levels, as set out in the Paris Agreement on Climate Change, could enable the world to avoid the type of melting the catastrophic sea level increases.

"This means we do not have to worry about any side effects of the loss of sea ice on the … (surface) melting in Greenland that is occurring due to the greenhouse effect," explained Professor Jens Hesselbjerg Christensen, a climate physics researcher. the Niels Bohr Institute in Copenhagen, Denmark, and one of the leading coordinators of the Ice2Ice project.

"However, the loss of sea ice in the Arctic is still alarming because it has a major impact on the ecosystems of the region."

Tracks

The Ice2Ice project has rebuilt as Arctic sea ice and Greenland ice sheets have responded to climate change in the past by analyzing Greenland's ice cores and the sediment cores of the bottom of the Arctic Ocean. They used this information to build a simulation of what can happen if the world continues to warm up.

"We did an experiment in which we had 15 ° C of global warming, which is too high to make all the sea ice disappear," said Professor Hesselbjerg Christensen. "Even so, the answer in Greenland just seemed to be driven by the global greenhouse effect, it has remained stable for hundreds of years and we have not been able to see much of the impact of sea ice loss." way after several hundred years.

While the simulation of this extreme warming may seem unrealistic, parts of the Arctic are already experiencing sudden local temperature changes that could mimic it in the coming decades.

"If you look around Svalbard (on the border of the Arctic Ocean), we have seen very large temperature changes over the last 40 years – something on the order of 2 ° C per decade," said Prof. Hesselbjerg Christensen. "If this continues for 100 years then the (local) warming would be very strong."

While it is estimated that global temperatures have risen by about 1 ° C compared to those in pre-industrial times, this is an average increase around the world. Some areas will experience greater warming – such as the Arctic – while others will not.

"One of the problems we have is that the Arctic is still not really well understood."

Professor Garry Peterson, Stockholm Resilience Center, Sweden

This has led many to consider the Arctic as a kind of canary in the coal mine for what may be reserved as the world continues to warm up. The Stockholm Resilience Center in Sweden has recently identified 19 regime changes that it considers markers of how climate change is transforming the Arctic.

It has been found that there is already evidence of 15 such regime changes occurring in the Arctic, as climate warming causes irreversible changes in land vegetation and ocean ecosystems.

"The Arctic is the forerunner of climate change around the world, as it is generally warming twice as much as the global average," said Professor Garry Peterson, an environmental scientist at the Stockholm Resilience Center. "There is growing concern about how the loss of sea ice is changing global weather patterns."

Flames

A recent study published last year in Nature found evidence that Arctic ice loss can affect precipitation patterns around the world, triggering an increase in droughts and fires in places like California, which this year has seen devastating flames in their cities. .

"One of the problems we have is that the Arctic is still not very well understood," said Prof. Peterson. "There is relatively little monitoring going on in the Arctic compared to other parts of the world. So we are likely to see some more surprises as the Arctic continues to change.

Most of our knowledge of the changes currently occurring in the Arctic comes from satellite images showing reductions in sea ice in the summer over the last 40 years. Unfortunately, to really understand whether these are due to humanity's influence on climate or natural variations on the environment, they need data that goes back to the past.

The IceDynamO project is attempting to build a high-resolution reconstruction of sea ice cover in the Arctic Ocean, off the coast of the northeastern ice sheet of Greenland. Using information stored in the sediment at the bottom of the ocean, the project's researchers are gathering how sea ice has varied over the past millennia and how the ocean and atmospheric conditions may have influenced that.

Sediment cores from the seabed contain fossil and chemical clues about when the sea was frozen in the past. Image Credit - Dr. Christof Pearce

"If we can see what has happened over the last 2,000 years, we can see what the natural variations in sea ice were before humans began to influence it," said Teodoro Pados, a geoscientist at Aarhus University in Denmark. principal investigator of the project. "We need to understand what the natural variation of sea ice has been in the recent past and what caused it."

Although the project started only earlier this year, the results should help inform scientists' attempts to build models of how the Arctic is expected to change in the coming years. The fate of the region can have profound implications not only for those who live there but also for other parts of the world.

"The variability in sea ice influences large-scale climatic phenomena that have an impact on other parts of the world," said Pados. "A recent study has shown that it can influence climate in the mid-latitudes of Europe, for example, and is also known to influence the deep water conveyor belt that transports water around the world. what will be the full effects if we lose sea ice.

The research in this article has been funded by the EU. If you liked this article, consider sharing it on social media.


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