They studied molecules from certain algae that are only produced when there is sea ice. Natural climate variation alone was all it took to reach the required temperature level.
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The “Last Ice Area” north of Greenland and Canada is the last sanctuary of all-year sea ice in this time of rising temperatures caused by climate change.
A new study now suggests that this may soon be over, says Phys.org.
Researchers from Aarhus University, in collaboration with Stockholm University and the United States Geological Survey, analyzed samples from the previously inaccessible region north of Greenland.
The sediment samples were collected from the seabed in the Lincoln Sea, part of the “Last Ice Area”. They showed that the sea ice in this region melted away during summer months around 10,000 years ago.
The research team concluded that summer sea ice melted at a time when temperatures were at a level that we are rapidly approaching again today.
“Climate models have suggested that summer sea ice in this region will melt in the coming decades, but it’s uncertain if it will happen in 20, 30, 40 years, or more. This project has demonstrated that we’re very close to this scenario, and that temperatures only have to increase a little before the ice will melt,” says Christof Pearce, Assistant Professor at the Department of Geoscience, Aarhus University.
The researchers have used data from the Early Holocene period to predict when the sea ice will melt today. During this time period, summer temperatures in the Arctic were higher than today. Although this was caused by natural climate variability opposed to the human-induced warming, it still is a natural laboratory for studying the fate of this region in the immediate future.
In Aarhus the marine samples have been analyzed in collaboration with Associate Professor Marianne Glasius and academic technical staff Mads Mørk Jensen from the Department of Chemistry.
Among other things, they studied molecules from certain algae that are only produced when there is sea ice. The researchers can thereby determine when summer sea ice was present in the area.
Full article here.
Tallbloke's Talkshop 
Izzat so? Among other things, they studied molecules from certain algae,, I’ve got some in my work pockets too – they’ve been a’ ower the place. Dog loves chewing over the data – even when contaminated with oil !
Summer sea ice disappearance ? eh? this morning on other posting, I was talking about , if you like, Summer Ice ARRIVING this now ( around Spring equinox, to be pedantic.) but not making a thing about it. Just that MSM doesn’t like to talk about it: Why does everything have to revolve around “sex” with them – to go to Alpine Switzerland … ah I forgot it was that Toblerone story – and not the one about the Bear on the Matterhorn either and concoct a story with the local bear. Well maybe ‘cos the bear has gone from the Matterhorn, there would be the matter of the ice going too? weird. Webcams show otherwise IMHO.
And as we know, after the early holocene with its ice free Arctic, the climate went into a runaway positive feedback, and, erm (checks notes) the temperature declined all the way to the nadir of the little ice age.
Have they got an attribution study for the Holocene sea ice melt yet? Surely they must have candidates at least 😎
Maybe a volcano or three (hundred?) – or maybe not.
Reblogged this on Climate Collections.
Never mind the algae. 19th century explorers found surprising amounts of open water.
Fig.2. The ship tracks and winter-over locations of Arctic discovery expeditions from 1818 to 1859 are surprisingly consistent with present sea ice climatology (contours represented by shades of blue). The climatology shown reflects percent frequency of sea ice presence on 10 September which is the usual date of annual ice minimum for the reference period 1971–2000 (Canadian Ice Service,2002). On a number of occasions,expeditions came within 150 km of completing the Northwest Passage, but even in years with unfavorable ice conditions, most ships were still able to reach comparatively advanced positions within the Canadian archipelago. By 1859, all possible routes comprising the Northwest Passage had been discovered.
This drawing from the vicinity of Beechey Island illustrates the situation of the H.M.S.Resolute and the steam-tender Pioneer on 5 September 1850 [from Facsimile of the Illustrated Arctic News,courtesy of Elmer E.Rasmuson Library,Univ.of AlaskaFairbanks].
Great image Ron, thanks for posting.
In the twitter thread, lots of criticism about that RB Alley graph because it ends in 1885. Of course ice cores are proxies for temperature changes over centuries and millenia (low resolution) not directly comparable to high resolution instrumental records. And recently frozen Greenland or Antarctic ice cannot be used. Still RB Alley did a later publication presenting ice core temperature in thousands of years prior to 1950.
It does look like most of the last 10,000 years were warmer than the most recent part. No one knows what decadal or centennial fluctuations occurred in the past to compare with the modern temperature record.
So it’s been ice-free before because natural variability raised the temperature but there’s no way rising temperatures now can be natural variability? This study simply disproves climate change, and pretending it somehow does not is preposterous. We now have a vast amount of evidence showing natural variation has caused temperatures higher than current temperatures through much of the last 10-50,000 years, including periods of rapid increase. How can scientists continue with this charade?
If temperature has risen around 1C since 1885, that would put Greenland at around the same temperature as during the Medieval Warm Period. However, the Vikings were managing to do some subsistence farming on Greenland back then. Livestock farming was moderately successful in the first half of the C20th, but was pretty much wiped out by bad winters in the 60s and 70s. Nowadays, there are a few sheepfarms and turnip patches in the south, around the orginal norse settlements.
This page gives an overview and is an interesting read.
http://www.kujataa.gl/en-gb/Agriculture-in-Greenland
[…] Summer sea ice disappearance from the Arctic has happened before, say researchers […]
tallbloke:
according to a recent article (which I didn’t record) there was proof that the early Vikings grew barley in Greenland. Would the Vikings do without Ale?
Fits in with claims that they grew wheat, barley and oats in Iceland, but stopped growing these in the Little Ice Age, and only resumed growing barley in 1924 (“after 400 years”) during the warming after approx. 1905. Wheat has been grown for about 15 years, but a specially bred Winter Wheat — planted after the autumn harvest and mulched with (insulating) seaweed in winter, and only near the sea.
Fits in with the claim by Brian Fagan in The Little Ice Age that wheat was grown north of Trondheim in the medieval warming period. Tronheim is at the same latitude as southern Iceland. (Fagan is a believer in Man Made Warming and was a Professor in California).
[…] From Tallbloke’s Talkshop […]
Ice melts because the global mean surface temperature is above 0°C. Only melting of ice on land can raise sea level, and the rate of such increase has not increased in the last 200 years. This is because carbon dioxide and methane have nothing to do with climate change, this being controlled by variations in the intensity of cosmic rays which assist cloud formation. As sunspot activity increases the heliosphere expands and this shields more cosmic rays from reaching Earth, thus causing global warming. But the sunspot activity is starting to decrease because we are close to the maximum of a ~1,000 year natural cycle, possibly regulated by the eccentricity of Jupiter which may have an effect on the solar activity. Read https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4386467
[reply] Link to Doug Cotton’s paper:
https://www.researchgate.net/publication/337915638_Understanding_Josef_Loschmidt's_Gravito-_Thermal_Effect_and_thus_Why_the_Radiative_Forcing_Greenhouse_Hypothesis_is_False/link/5df2c4b1a6fdcc28371d1ed8/download