Claim: Last 100 years may be warmest in 120,000 years in the Arctic, but not so fast (UPDATED)

From the University of Colorado at Boulder, comes this study about radiocarbon dating some dead moss clumps exposed from under ice/snow at 4 locations on Baffin Island that somehow proves “unprecedented” warmth for the entire Arctic for the last 120,000 years. See below for my take on it.

CU-Boulder study shows unprecedented warmth in Arctic

The heat is on, at least in the Arctic.

Average summer temperatures in the Eastern Canadian Arctic during the last 100 years are higher now than during any century in the past 44,000 years and perhaps as long ago as 120,000 years, says a new University of Colorado Boulder study.

The study is the first direct evidence the present warmth in the Eastern Canadian Arctic exceeds the peak warmth there in the Early Holocene, when the amount of the sun’s energy reaching the Northern Hemisphere in summer was roughly 9 percent greater than today, said CU-Boulder geological sciences Professor Gifford Miller, study leader. The Holocene is a geological epoch that began after Earth’s last glacial period ended roughly 11,700 years ago and which continues today.

Miller and his colleagues used dead moss clumps emerging from receding ice caps on Baffin Island as tiny clocks. At four different ice caps, radiocarbon dates show the mosses had not been exposed to the elements since at least 44,000 to 51,000 years ago.

Since radiocarbon dating is only accurate to about 50,000 years and because Earth’s geological record shows it was in a glaciation stage prior to that time, the indications are that Canadian Arctic temperatures today have not been matched or exceeded for roughly 120,000 years, Miller said.

“The key piece here is just how unprecedented the warming of Arctic Canada is,” said Miller, also a fellow at CU-Boulder’s Institute of Arctic and Alpine Research. “This study really says the warming we are seeing is outside any kind of known natural variability, and it has to be due to increased greenhouse gases in the atmosphere.”

A paper on the subject appeared online Oct. 21 in Geophysical Research Letters, a journal published by the American Geophysical Union. Co-authors include CU-Boulder Senior Research Associate Scott Lehman, former CU-Boulder doctoral student and now Prescott College Professor Kurt Refsnider, University of California Irvine researcher John Southon and University of Wisconsin, Madison Research Associate Yafang Zhong. The National Science Foundation provided the primary funding for the study.

Miller and his colleagues compiled the age distribution of 145 radiocarbon-dated plants in the highlands of Baffin Island that were exposed by ice recession during the year they were collected by the researchers. All samples collected were within 1 meter of the ice caps, which are generally receding by 2 to 3 meters a year. “The oldest radiocarbon dates were a total shock to me,” said Miller.

Located just east of Greenland, (um, no, to the west – Anthony) the 196,000-square-mile Baffin Island is the fifth largest island in the world. Most of it lies above the Arctic Circle. Many of the ice caps on the highlands of Baffin Island rest on relatively flat terrain, usually frozen to their beds. “Where the ice is cold and thin, it doesn’t flow, so the ancient landscape on which they formed is preserved pretty much intact,” said Miller.

To reconstruct the past climate of Baffin Island beyond the limit of radiocarbon dating, Miller and his team used data from ice cores previously retrieved by international teams from the nearby Greenland Ice Sheet.

The ice cores showed that the youngest time interval from which summer temperatures in the Arctic were plausibly as warm as today is about 120,000 years ago, near the end of the last interglacial period. “We suggest this is the most likely age of these samples,” said Miller.

The new study also showed summer temperatures cooled in the Canadian Arctic by about 5 degrees Fahrenheit from roughly 5,000 years ago to about 100 years ago – a period that included the Little Ice Age from 1275 to about 1900.

“Although the Arctic has been warming since about 1900, the most significant warming in the Baffin Island region didn’t really start until the 1970s,” said Miller. “And it is really in the past 20 years that the warming signal from that region has been just stunning. All of Baffin Island is melting, and we expect all of the ice caps to eventually disappear, even if there is no additional warming.”

Temperatures across the Arctic have been rising substantially in recent decades as a result of the buildup of greenhouse gases in Earth’s atmosphere. Studies by CU-Boulder researchers in Greenland indicate temperatures on the ice sheet have climbed 7 degrees Fahrenheit since 1991.

A 2012 study by Miller and colleagues using radiocarbon-dated mosses that emerged from under the Baffin Island ice caps and sediment cores from Iceland suggested that the trigger for the Little Ice Age was likely a combination of exploding tropical volcanoes – which ejected tiny aerosols that reflected sunlight back into space – and a decrease in solar radiation.

-CU-

Contact:

Gifford Miller, 303-492-6962, cell 303-990-2071

gmiller@colorado.edu

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I don’t dispute validity of radio-carbon14 dating techniques, but I think there is a logic failure in the claim being made.

The claim is that these plants haven’t been exposed for thousands of years, as dated by the C14 isotope.

At four different ice caps, radiocarbon dates show the mosses had not been exposed to the elements since at least 44,000 to 51,000 years ago.

That might be true, but then again they are long dead, so there wouldn’t be any uptake of new C14 if they were exposed to the open air in the past. There’s no claim that the mosses are now suddenly alive and growing again. So, if they had been “exposed to the elements” since then, they would not have an new C14 in them unless they came back to life and conducted photosynthesis.

Since plant material in the Arctic doesn’t decay like it does elsewhere due to low temperature and low humidity, it could very well remain intact while exposed for quite some time. All I think they can claim is that the plants haven’t been alive for 44,000 to 120,000 years. I don’t think they can’t prove with C14 dating that they have not been exposed then reburied under ice/snow since then. Ice is a funny thing, it can melt due to warmer temperatures or it can sublimate at below freezing temperatures if there’s not enough sustaining precipitation, as we know from Mount Kilimanjaro. What I’d really like to see is what the receding ice edge looks like. Sublimation leaves a signature that is quite different from melting.

Studies by CU-Boulder researchers in Greenland indicate temperatures on the ice sheet have climbed 7 degrees Fahrenheit since 1991.

Greenland is not Baffin island. You can’t just say that a temperature change in one place automatically means a similar temperature change in another place. Similarly, Baffin island isn’t the entire “Arctic”, yet it is portrayed in the press release as if this one proxy indicator of four sampled sites represents the entire Arctic temperature experience back 120,000 years.  It’s Yamal all over again.

Recall our series of stories about “midges” used for proxy temperature reconstruction on Baffin island: Baffin Island Midge Study – debunked for a 3rd time – nearby weather station shows no warming.

This weather station on Baffin Island [Clyde Meteorological station]  shows no summer temperature increase in the last 50 years. Summer matters most because that’s the melt season.

So what’s going on with the receding ice edge on Baffin island; is it melting or sublimating? Inquiring minds want to know.  From the one photo they provided, it is hard to tell:

Of course the uncritical MSM is already trumpeting this story without question, with the usual bent that the posited current warmth is a bad thing.

What really bugs me (besides the fact the press release can’t even bother to mention the title of the study) is that they use of the word “unprecedented” in the title of the press release. Obviously this isn’t true, because it had to be warm enough, long enough, back then to give these mosses a chance to get a foothold and grow. If the warmth today was “unprecedented” they’d find nothing in the way of previous life forms under the receding ice. – Anthony

UPDATE: 10/25/13 11AM PDT

I lamented the lack of photographs to show me what sort of ice loss signature there was. The press release at AGU had such a photo in it which I show below, click for a much larger version.

Looking at the stream channels, clearly this is mostly a melt process, but did you notice the most important distinction?

Note the albedo difference from the ice cap on the left side versus the right side. The right side is almost pure white, and there are no stream channels. The left side has lots of stream channels and is a dirty brown. Notice also that the ice in surrounding depressions is whiter that the ice cap, which is actually a small hill, though I don’t know what height it is above surrounding terrain.

What this looks like to me is that the windward side of the Sputnik icecap hill is on the left and it is picking up all sorts of debris and particulates (such as carbon soot) on the leeward side there is less deposition, and the ice is cleaner.

As we’ve noted before on WUWT, carbon soot is a big problem in the Arctic.

I’d really like to know why the authors have not mentioned what is obvious to the eye as an alternate possibility for the icecap decline.