Intense warm climate intervals–warmer than scientists thought possible–have occurred in the Arctic over the past 2.8 million years.
That result comes from the first analyses of the longest sediment cores ever retrieved on land. They were obtained from beneath remote, ice-covered Lake El’gygytgyn (pronounced El’gee-git-gin) (“Lake E”) in the northeastern Russian Arctic.
The journal Science published the findings this week.
They show that the extreme warm periods in the Arctic correspond closely with times when parts of Antarctica were also ice-free and warm, suggesting a strong connection between Northern and Southern Hemisphere climate.
The polar regions are much more vulnerable to climate change than researchers thought, say the National Science Foundation-(NSF) funded Lake E project’s co-chief scientists: Martin Melles of the University of Cologne, Germany; Julie Brigham-Grette of the University of Massachusetts Amherst; and Pavel Minyuk of Russia’s North-East Interdisciplinary Scientific Research Institute in Magadan.
The exceptional climate warming in the Arctic, and the inter-hemispheric interdependencies, weren’t known before the Lake E studies, the scientists say.
Lake E was formed 3.6 million years ago when a huge meteorite hit Earth, leaving an 11-mile-wide crater. It’s been collecting layers of sediment ever since.
The lake is of interest to scientists because it has never been covered by glaciers. That has allowed the uninterrupted build-up of sediment at the bottom of the lake, recording hitherto undiscovered information on climate change.
Cores from Lake E go far back in time, almost 30 times farther than Greenland ice cores covering the past 110,000 years.
The sediment cores from Lake El’gygytgyn reflect the climate and environmental history of the Arctic with great sensitivity, say Brigham-Grette and colleagues.
The physical, chemical and biological properties of Lake E’s sediments match the known global glacial/interglacial pattern of the ice ages.
Some warm phases are exceptional, however, marked by extraordinarily high biological activity in the lake, well above that of “regular” climate cycles.
To quantify the climate differences, the scientists studied four warm phases in detail: the two youngest, called “normal” interglacials, from 12,000 years and 125,000 years ago; and two older phases, called “super” interglacials, from 400,000 and 1.1 million years ago.
According to climate reconstructions based on pollen found in sediment cores, summer temperatures and annual precipitation during the super interglacials were about 4 to 5 degrees C warmer, and about 12 inches wetter, than during normal interglacials.
The super interglacial climates suggest that it’s nearly impossible for Greenland’s ice sheet to have existed in its present form at those times.
Simulations using a state-of-the-art climate model show that the high temperature and precipitation during the super interglacials can’t be explained by Earth’s orbital parameters or variations in atmospheric greenhouse gases alone, which geologists usually see as driving the glacial/interglacial pattern during ice ages.
That suggests that additional climate feedbacks are at work.
“Improving climate models means that they will better match the data that has been collected,” says Paul Filmer, program director in NSF’s Division of Earth Sciences, which funded the “Lake E” project along with NSF’s Office of Polar Programs.
“The results of this collaboration among scientists in the U.S., Austria, Germany and Russia are providing a challenge for researchers working on climate models: they now need to match results from Antarctica, Greenland–and Lake El’gygytgyn.”
Adds Simon Stephenson, director of the Division of Arctic Sciences in NSF’s Office of Polar Programs, “This is a significant result from NSF’s investment in frontier research during the recent International Polar Year.
“‘Lake E’ has been a successful partnership in very challenging conditions. These results make a significant contribution to our understanding of how Earth’s climate system works, and improve our understanding of what future climate might be like.”
The scientists suspect the trigger for intense interglacials might lie in Antarctica.
Earlier work by the international ANDRILL program discovered recurring intervals when the West Antarctic Ice Sheet melted. (ANDRILL, or the ANtarctic geological DRILLing project, is a collaboration of scientists from five nations–Germany, Italy, New Zealand, the United Kingdom and the United States–to recover geologic records from the Antarctic margin.)
The current Lake E study shows that some of these events match with the super interglacials in the Arctic.
The results are of global significance, they believe, demonstrating strong indications of an ongoing collapse of ice shelves around the Antarctic Peninsula and at the margins of the West Antarctica Ice Sheet–and a potential acceleration in the near future.
The Science paper co-authors discuss two scenarios for future testing that could explain the Northern Hemisphere-Southern Hemisphere climate coupling.
First, they say, reduced glacial ice cover and loss of ice shelves in Antarctica could have limited formation of cold bottom water masses that flow into the North Pacific Ocean and upwell to the surface, resulting in warmer surface waters, higher temperatures and increased precipitation on land.
Alternatively, disintegration of the West Antarctic Ice Sheet may have led to significant global sea level rise and allowed more warm surface water to reach the Arctic Ocean through the Bering Strait.
Lake E’s past, say the researchers, could be the key to our global climate future.
The El’gygytgyn Drilling Project also was funded by the International Continental Scientific Drilling Program (ICDP), the German Federal Ministry for Education and Research, Alfred Wegener Institute, GeoForschungsZentrum-Potsdam, the Russian Academy of Sciences Far East Branch, the Russian Foundation for Basic Research, and the Austrian Ministry for Science and Research.
In my travels around Arctic regions I have always been struck by the presence of plants and soil conditions in Siberia consistent with it having had a warmer climate for most of its history, and the total lack of developed soil conditions even in fairly southern regions of the Hudson Bay region of Canada. How could Alaska and Siberia have developed soils while the Eastern Arctic of Canada and the island of Greenland have almost no soil at the same latitudes? Unless, of course, the position of the North Pole had shifted in geologically recent times. We know that the position of the magnetic North pole is always shifting, and that the actual position of the geographic pole might also have shifted in the relatively recent past.
Evidence of this is now confirmed by these new findings in Lake E., a region never experiencing glacial movements during the past 2 million years and more. Observe that the samples revealed developed soil, soil and debris consistent with developed soil regions–impossible for a region in the grip of Arctic conditions.
At the same time we observe in the Southern regions of Hudson Bay in Canada, that even while the climate there now is far more mild than in Siberia, yet soil conditions are almost nonexistent, with muskeg, mosses, lichens predominating. How could this situation exist were the present position of the North Pole have been maintained over the intervening millions of years?
Thus, logically, the North Pole was closer to the Canadian side and more remote from the Siberian side in the more recent geological past.
An estimate of the North Pole’s position just prior to its present position, and using the available evidence from soil samples, might put it in Melville Bay, between Greenland and Canada. If the recently past position of the North Pole were to have been in Melville Bay then that would explain why there is no soil development even in southern parts of Central Canada’s Hudson Bay region, while microorganisms consistent with more mature soil development being made possible from a warmer climate, what would occur if the North Pole and the corresponding Arctic region were more on the Canadian side and more remote from the Siberian side.
It is time to follow the evidence and put our beliefs and ideologies aside.
Dalton Garis
New York