Greenland caves reveal climate drivers beyond temperature

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By Danielle Prieur –

Paleoclimatologist Gina Moseley found an old Kodak film box when she entered a cave in northeast Greenland last year? It gave her the clue that few people had stopped there since the 1960s. An American scientist left behind a note in the 1960s film box and it was untouched when Moseley and her team found it. Probably few people had stopped there since.

She and her team discovered some new caves in the hostile and hard to reach environment of the 26 caves they explored.

Mineral formations called speleothems formed by rainwater and carbon dioxide slowly dissolve carbonates such as limestone above the caves and then redeposit them inside the caves where they seep. These dramatic spindles and towers of stalagmites and stalactites offer scientists clues as to prehistoric climate patterns.

“From what we understand no one had entered these upper, higher level caves,” said Moseley, a post-doctorate researcher at the University of Innsbruck, Austria. That’s because of the arduous climb to reach the caves across an almost Alpine ski slope, she said, speaking to colleagues at the Comer Abrupt Climate Change Conference in Wisconsin this fall.  .

As part of the Northeast Greenland Caves Project, Moseley and her team, know that half of the field research is getting to the site. For this study alone, the science team “flew up the east coast of Greenland,” she said. “Then we crossed the lake about 20 km wide in an inflatable boat and finally set up base camp on the east shore and hiked to where the caves are.”

Although Moseley and her team now hold the record for the “most northerly explored cave on the face of the planet,” they also hold a much more important scientific one: the first speleothem paleoclimate record of Greenland.

A speleothem or flowstone formation on a wall, floor or ceiling of a cave that can be studied to determine temperature and evaporation at a particular time.

“That’s interesting because today the region is too arid and it’s a permafrost zone, so you wouldn’t have any modern calcite deposition in the caves,” Moseley said. “Their presence means, at some point in the past, it must have been warmer and wetter for water to flow and for the flowstone to form.”

What Moseley and her team found in these caves is a treasure trove for scientists. “We found flowstone everywhere,” she said. “Even though there was so much material…we found a thinner flowstone and this was the youngest material and we took some of this.”

By the end of their field research, Moseley and her team had, “documented 26 caves, collected 16 calcite samples, three water samples, two sediment samples and one bone and feather sample,” enough to generate a record and to question her own hypothesis  “about what controls oxygen isotope composition in the speleothems.”

“Instead, we need to look at seasonality or something else…temperature’s not the main control,” Moseley hypothesized. Until she can perform further research to determine what controls this the oxygen isotope composition so crucial to speleothem deposition in caves, her uranium-thorium dating completed so far of her speleothem samples has generated a record for the first time in these caves.

“There was quite a nice spread of age in the Holocene,” she said. The holocene is our own epoch in time, going back 10,000 years. But flowstones come from much earlier marine isotope stages, placing their deposition between 220,000 and 550,000 years ago, Moseley said.

Moseley’s hypothesis could mean that seasonal changes, as a result of climate change, affect the control of speleothem formation.

The team is planning to uranium-thorium date these samples and to radiocarbon-date a dead bird. The bird “appeared to be much larger than anything else we had seen there,” indicating that it’s possibly very old and from a different climate.

Moseley came to Greenland to “find out when it was warmer and wetter than it is now and get more information about climate during those warm intervals,” she said. She accomplished both while setting records in cave exploration. Her future field research holds “huge potential for extending the record.” By extending it, Moseley said she and scientists like her help improve climate predications for the future and understand better what might lead to extreme changes in temperature and climate.
Nov. 20, 2017

Photo at top: Gina Moseley and the research team in Greenland. (Courtesy of the Northeast Greenland Caves Project)

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