A sharp rise in Greenland temperatures since 1995 showed the giant northern island to be 2.7 degrees (1.5 degrees Celsius) warmer than its 20th-century average, the warmest in more than 1,000 years, according to new data. of ice cores.
Until now, Greenland’s ice cores, a look at long-term temperatures before the thermometers, hadn’t shown a clear sign of global warming in the more remote north central part of the island, at least compared to the rest. of the world. But the ice cores hadn’t been updated since 1995 either. The newly analyzed cores, drilled in 2011, show a dramatic rise in temperature over the previous 15 years, according to a study published Wednesday in the journal Nature.
“We kept (seeing) temperatures increasing between 1990 and 2011,” said the study’s lead author, Maria Hoerhold, a glaciologist at the Alfred Wegener Institute in Germany. “Now we have a clear sign of global warming.”
It takes years to analyze ice core data. Hoerhold has new cores from 2019 but hasn’t finished studying them yet. She expects the temperature rise to continue as Greenland’s ice sheet and glaciers have been melting faster recently.
“This is an important finding and corroborates the suspicion that the ‘missing warming’ in the ice cores is due to the fact that the cores end before the strong warming begins,” said climatologist Martin Stendel of the Danish Meteorological Institute. Who was? It’s not part of the investigation.
The ice cores are used to plot approximate temperatures for Greenland from the year 1000 to 2011. It shows temperatures gently descending towards a colder level for the first 800 years, then rising and falling as they warm to a sharp peak. and sudden hotter from the 1990s onwards. One scientist compared it to a hockey stick, a description used for other long-term temperature data showing climate change.
The jump in temperature after 1995 is much greater than it was in pre-industrial times before the mid-19th century, so there’s a “near zero” chance that it’s something other than human-caused climate change, Hoerhold said.
The warming spike also reflects a sudden increase in the amount of water escaping from Greenland’s melting ice, the study finds.
What had been happening in Greenland is that natural climate variability — ripples due to an occasional weather system called the Greenland lock — had in the past masked human-caused climate change, Hoerhold said.
But from about 25 years ago, the warming became too big to hide, he said.
Previous data also showed that Greenland is not warming as fast as the rest of the Arctic, which is now warming four times faster than the global average. But the island seems to be catching up.
Ice core data over the years showed that Greenland acted a bit differently than the Arctic. That is likely due to the Greenland blockade, Hoerhold said. Other scientists said that as a giant land mass, Greenland was less affected by melting sea ice and other water factors compared to the rest of the Arctic, which is much more adjacent to water.
Hoerhold’s team drilled five new cores near old cores to match established ice core records. They use the difference between two different types of oxygen isotopes found in the ice to calculate the temperature, using an already established formula that is compared to observed data.
Hoerhold and outside scientists said the new warming data is bad news because Greenland’s ice sheet is melting. In fact, the study ends with data from 2011 and the following year saw record melting in Greenland, and ice loss from the island has been high ever since, he said.
“We should be very concerned about the warming of northern Greenland because that region has a dozen sleeping giants in the form of wide tidal glaciers and an ice stream,” said Danish Meteorological Institute ice scientist Jason Box. And when it wakes up, Greenland’s melting will increase, he said.
And that means “rising seas threatening homes, businesses, economies and communities,” said Twila Moon, deputy principal scientist at the US National Snow and Ice Data Center.
Maria Hörhold, Modern temperatures in north-central Greenland are the warmest in the last millennium, Nature (2023). DOI: 10.1038/s41586-022-05517-z. www.nature.com/articles/s41586-022-05517-z
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Citation: New Ice Core Analysis Shows Strong Increase in Warming in Greenland (21 Jan 2023) Accessed 21 Jan 2023 at https://phys.org/news/2023-01-ice-core-analysis- sharp-greenland.html
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