New ice core analysis shows sharp warming spike in Greenland

New ice core analysis shows sharp warming spike in Greenland

New ice core analysis shows sharp warming spike in Greenland

New ice core analysis shows sharp warming spike in Greenland

A boat navigates next to large icebergs near the town of Kulusuk in east Greenland at night, August 15, 2019. A sharp rise in temperature in Greenland since 1995 showed the vast North Island was 2.7 degrees (1.5 degrees Celsius) hotter than the 20th-century average, the warmest in more than 1,000 years, according to new ice core data. Credit: AP Photo/Felipe Dana, file

A sharp rise in temperature in Greenland since 1995 showed the vast North Island was 2.7 degrees (1.5 degrees Celsius) hotter than its 20th-century average, the warmest in more than 1,000 years, according to new ice core data.

Until now, Greenland ice cores — a glimpse of long-running temperatures in front of thermometers — hadn’t shown a clear signal of global warming in the far northern part of the island, at least compared to the rest of the world. But the ice cores have not been updated since 1995 either. Re-analyzed core drilled in 2011 shows a dramatic increase in temperature over the past 15 years, according to a study in the journal Nature Wednesday.

“We continue to see rising temperatures between the 1990s and 2011,” said the study’s lead author Maria Hoerhold, a glaciologist at the Alfred Wegener Institute in Germany. “We now have a clear signature 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 at a faster rate lately.

“This is an important finding and strengthens the suspicion that the ‘lack of warming’ in the ice cores is due to the cores ending before the strong warming begins,” said climate researcher Martin Stendel from the Danish Meteorological Institute not part of the research.

The ice cores will be used to create a graph of proxy temperatures for Greenland running from the year 1000 to 2011. It shows temperatures falling slightly cooler for the first 800 years, then jiggling up and down as they get warmer until a sharp and sudden spike becomes hotter in the 1990s. One scientist compared it to a hockey stick, a description used for other long-term temperature data showing climate change.

The temperature jump after 1995 is so much larger than in the pre-industrial period before the mid-19th century that there is “nearly zero” probability that climate change is anything but man-made, Hoerhold said.

The warming spike also reflects a sudden increase in the amount of water draining from Greenland’s melting ice sheet, the study finds.

What happened in Greenland is that natural weather variability, wave action due to an occasional weather system called the Greenland Blockage, has historically masked human-caused climate change, Hoerhold said.

But about 25 years ago, the warming became too big to hide, she 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 years showed that Greenland behaved slightly differently than the Arctic. That’s likely due to Greenland’s lockdown, Hoerhold said. Other scientists said Greenland, as a huge landmass, was less affected by melting sea ice and other water factors than the rest of the Arctic, which is much more water-bound.

Hoerhold’s team drilled five new cores near old cores to match the established ice core records. They use the difference between two different types of oxygen isotopes found in ice to calculate temperature using an already established formula that is compared to observed data.

Hoerhold and outside scientists said the new warming data is bad news as Greenland’s ice sheet is melting. In fact, the study ends with data from 2011 and the next year there was a record meltdown across Greenland and the island’s ice loss has been high ever since, she 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 tidewater glaciers and an ice stream,” said Jason Box, ice scientist at the Danish Meteorological Institute. And when it wakes up, it will ramp up Greenland’s meltdown, he said.

And that means “rising seas that are threatening homes, businesses, economies and communities,” said Twila Moon, deputy chief scientist at the US National Snow and Ice Data Center.

More information:
Maria Hörhold, Modern temperatures in Central-Northern Greenland warmest in the past 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 Sharp Warming Spike in Greenland (2023, January 21) Retrieved January 21, 2023 from https://phys.org/news/2023-01-ice-core-analysis-sharp-greenland.html

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