Bugs in Greenland Mud Yield Clues to Future Warming

Temperatures on the island after the last ice age were higher than previously thought, a finding that will help estimate the impact of a warming climate.

The Northwestern team hikes in northwest Greenland near the country's vast ice sheet. | Yarrow Axford, Northwestern University
The Northwestern team hikes in northwest Greenland near the country's vast ice sheet. | Yarrow Axford, Northwestern University

Flying bugs trapped deep in the frozen mud covering Greenland have pointed researchers to new clues about the country’s climate, suggesting the now-icebound island was once warmer than previously believed.  

In the centuries that followed the last ice age and in the millenia between the last two, Greenland could have seen summer highs between 10 and 15 degrees warmer than today, according to a new study led by researchers at Northwestern University in Illinois.

Core samples taken from the mud of a lake bed in northwestern Greenland, just beyond the edge of the ice sheet and largely undisturbed by its historical ebb and flow, revealed large numbers of preserved insects known as phantom midges and a fly species known as chironomids. Those species today usually live well south of Greenland, but the numbers found in the sediment cores taken by the Northwestern team were comparable to populations seen in the Canadian Atlantic provinces.

As far as the team could tell, the phantom midge hasn’t been seen in Greenland before now.

“We think this is the first time anyone has reported it in ancient sediments or modern lakes there," Yarrow Axford, the study's senior author, said in a statement accompanying the findings. "We were really surprised to see how far north it migrated."

The findings suggest temperatures in Greenland’s summer might have ranged into the 50s Fahrenheit, or in the low teens Celsius — well above today’s averages of around 40°F.

The Northwestern team pulls a core of sediment from the bed of Wax Lips Lake. | Alex P. Taylor

With the Arctic warming today at twice the rate of the rest of the globe, Greenland is under intense scientific scrutiny. About four-fifths of the island is covered by a sheet of ice more than a mile thick. That’s enough frozen water to raise global sea levels by about six meters (20 feet) if it melted — which it is, at a slow but accelerating rate.

Figuring out what Greenland’s climate was like in the past can help scientists figure out what may happen to it in the future as planet-warming carbon dioxide and other gases build up in Earth’s atmosphere. That data collected by studies like the Northwestern study can be fed into computer models to help fine-tune those estimates.

“These findings may portend large future warming in this high-latitude region,” the authors conclude.

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In the period between the last two ace ages — roughly 11,000 to 116,000 years ago — sea levels were as much as 30 feet higher than they are today.

"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," Axford said.