New Study: Ancient Greenland Was Much Warmer Than Previously Thought

Discovery helps researchers understand how Greenland’s ice sheet responds to warming

A tiny clue found in ancient sediment has unlocked big secrets about Greenland’s past and future climate.

Just beyond the northwest edge of the vast Greenland Ice Sheet, Northwestern University researchers have discovered lake mud that beat tough odds by surviving the last ice age. The mud, and remains of common flies nestled within it, record two interglacial periods in northwest Greenland. Although researchers have long known these two periods — the early Holocene and Last Interglacial — experienced warming in the Arctic due to changes in the Earth’s orbit, the mix of fly species preserved from these times shows that Greenland was even warmer than previously thought.

This information could help researchers better gauge Greenland’s sensitivity to warming, by testing and improving models of climate and ice sheet behavior. Those models could then improve predictions of how Greenland’s ice sheet, which covers 80 percent of the Arctic country and holds enough ice to equal 20 feet of global sea level, might respond to man-made global warming.

“Northwest Greenland might feel really remote, but what happens to that ice sheet is going to matter to everyone in New York City, Miami and every coastal city around the world,” said Yarrow Axford, the study’s senior author and an associate professor of Earth and planetary sciences in Northwestern’s Weinberg College of Arts and Sciences. “One of the big uncertainties in climate science remains how fast the Earth changes when it gets warmer. Geology gives us an opportunity to see what happened when the Earth was warmer than today.”

Published today, June 4, in the Proceedings of the National Academy of Sciences, the study included contributions from collaborators at Dartmouth College.

People might be surprised to see how today’s frigid Greenland looked during the past two interglacial periods. Today, northwest Greenland hovers in the 30s and low 40s Fahrenheit and weathers snowstorms in summer. But average summer temperatures in the early Holocene (8,000 to 11,000 years ago) and Last Interglacial (116,000 to 130,000 years ago) climbed well into the 50s. […]

The bigger picture

Discovering this mix of insects means northwest Greenland’s average July during the last two interglacial periods most likely climbed above 50 degrees and possibly into the high 50s during the Last Interglacial. This confirms controversial geological records constructed from ice cores taken nearby, which also indicated significant warming during these time periods.

“Other records have shown that northern Greenland’s climate was much warmer than people expected during those periods, and those results received justified skepticism,” Axford said. “Now we have an independent record that confirms that when the Arctic warmed in the past, there was especially strong warming in northern Greenland.”

This data will help the broader scientific community further hone climate and ice sheet models used to project future changes.

Full post

via The Global Warming Policy Forum (GWPF)

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June 5, 2018 at 06:26AM

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