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Frozen Greenland is set to become much less frozen before the end of the 21st century. By 2055, winter snowfall on the Greenland ice sheet will no longer be enough to replenish the ice that Greenland loses every summer, new research shows.
Rising global temperatures are behind this dramatic change. If the Earth continues to warm at its current rate, average global temperatures are expected to climb nearly 5 degrees Fahrenheit (2.7 degrees Celsius) by 2055. Regional averages in Greenland are getting even warmer, increasing by about 8 F (4.5 C), scientists reported in a new study.
Under these conditions, the annual loss of ice in Greenland could raise sea level up to 13 centimeters by 2100 – unless drastic measures are taken, now, to reduce greenhouse gas emissions and slow global warming tendencies.
Related: Photos of the magnificent glaciers of Greenland
Ice caps are thick masses of ice that cover more than 20,000 square miles (50,000 square kilometers) of land, and they push their icy layers from the snow that accumulates over thousands of years, according to the National Snow and Ice Data Center (NSIDC). During the last ice Age (around 115,000 to 11,700 years ago) ice caps covered much of North America and Scandinavia. But today, only two ice caps remain – in Greenland and Antarctic – holding about 99% of the Earth’s freshwater reserves, according to the NSIDC.
Ice caps aren’t static – their own weight pushes them slowly toward the ocean, where they dump ice and meltwater from ice shelves, streams, and glaciers. An ice cap can only remain stable as long as its lost ice is seasonally replenished by winter snowfall.
The Greenland ice sheet is about three times the size of Texas, measuring about 656,000 square miles (1.7 million square kilometers), according to the NSIDC. If all the ice in Greenland were to melt at the same time, the sea level would rise by about 6 meters. While this catastrophic scenario is unlikely to happen anytime soon, Greenland has been losing ice steadily for decades, at a rate of around 500 gigatons per year since 1999, another study published in August 2020 found.
These scientists said Greenland is already losing more ice than it is gaining each winter. Their models take into account the loss of ice due to the calving of icebergs, which can be substantial; a massive iceberg that broke apart and drifted alarmingly near a village in Greenland in 2018 weighed more than 12 million tonnes (11 million metric tonnes), Previously reported Live Science.
However, the processes that cause icebergs to separate from the ice sheet are complex and unpredictable, said Brice Noël, lead author of the new study and a researcher at the Institute for Marine and Atmospheric Research (IMAU) at the University of Paris. ‘Utrecht in the Netherlands. For the new study, the researchers analyzed the surface of the Greenland ice sheet to determine when the melt would overtake the snowfall, Noël told Live Science in an email.
“We are exploring the sensitivity of the mass loss of the Greenland ice sheet to atmospheric warming using a much higher resolution climate model – 1 km – compared to previous work (20 to 100 km),” said Noël. “Higher spatial resolution means we can now better capture the high rates of mass loss from small outlet glaciers;” this source of melt runoff was previously excluded from models, but contributes significantly to the total mass of ice lost, he explained.
“As a result, we can more accurately project the future course of the mass loss of the Greenland ice sheet and its contribution to sea level rise,” said Noël.
Accelerated exposure
According to the study, the stability of the ice sheet began to slip after the 1990s, as atmospheric warming increased meltwater runoff during the hot summer months. The models showed that most of the runoff was produced at the edges of the ice cap, in a narrow band called the ablation zone. As the Earth warms, it melts the tightly compressed protective layer of snow in the ablation zone. Once that layer is gone, the ice below – which is much less reflective than shiny snow – absorbs more sunlight, resulting in more melting.
“The accelerated exposure of bare ice amplifies the production of runoff, and therefore the loss of surface mass,” said Noël.
In a scenario where humans do not reduce greenhouse gas emissions and current warming continues, ice loss in Greenland will cross a new threshold – in which the ice sheet shrinks every year – in just a few decades, according to the study. And that’s a conservative estimate; this threshold could be crossed even earlier, depending on the amount of additional ice lost each year by calving icebergs, the authors reported.
It could then take thousands of years for the ice sheet to melt completely, but to prevent Greenland’s ice from disappearing, global warming would have to be stopped or reversed as soon as possible – “in this century,” he said. declared Christmas.
The results were published online Jan. 19 in the journal Geophysical research letters.
Originally posted on Live Science.
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