I love field work. I think any climate scientist that basically becomes a data jockey should be forced to go out and examine real world measurement systems and weather stations once a year so that they don’t lose touch with the source of the data they study. That’s why I’m pleased to see that scientists at the Geological Survey of Norway (NGU ) did some good old fashioned field work to look at geologic residues of past climate.
What they found was intriguing. The arctic may have periodically been nearly ice free in recent geologic history, after the last ice age. It is clear from this that we don’t really know as much as some think they do about climatic and ice cycles of our planet.
Recent mapping of a number of raised beach ridges on the north coast of Greenland suggests that the ice cover in the Arctic Ocean was greatly reduced some 6000-7000 years ago. The Arctic Ocean may have been periodically ice free.
BEACH RIDGE: The scientists believe that this beach ridge in North Greenland formed by wave activity about 6000-7000 years ago. This implies that there was more open sea in this region than there is today. (Click the picture for a larger image) Photo: Astrid Lyså, NGU
”The climate in the northern regions has never been milder since the last Ice Age than it was about 6000-7000 years ago. We still don’t know whether the Arctic Ocean was completely ice free, but there was more open water in the area north of Greenland than there is today,” says Astrid Lyså, a geologist and researcher at the Geological Survey of Norway (NGU).
Shore features
ICE COVER: Today, at the mouth of Independence Fjord in North Greenland, drift ice forms a continuous cover from the land. (Click for a larger image) Photo: Eiliv Larsen, NGU
Together with her NGU colleague, Eiliv Larsen, she has worked on the north coast of Greenland with a group of scientists from the University of Copenhagen, mapping sea-level changes and studying a number of shore features. She has also collected samples of driftwood that originated from Siberia or Alaska and had these dated, and has collected shells and microfossils from shore sediments.
SETTLEMENT: Astrid Lyså in August 2007 in the ruined settlement left by the Independence I Culture in North Greenland. The first immigrants to these inhospitable regions succumbed to the elements nearly 4000 years ago, when the climate became colder again. (Click for a larger image) Photo: Eiliv Larsen, NGU
”The architecture of a sandy shore depends partly on whether wave activity or pack ice has influenced its formation. Beach ridges, which are generally distinct, very long, broad features running parallel to the shoreline, form when there is wave activity and occasional storms. This requires periodically open water,” Astrid Lyså tells me.
Pack-ice ridges which form when drift ice is pressed onto the seashore piling up shore sediments that lie in its path, have a completely different character. They are generally shorter, narrower and more irregular in shape.
Open sea
”The beach ridges which we have had dated to about 6000-7000 years ago were shaped by wave activity,” says Astrid Lyså. They are located at the mouth of Independence Fjord in North Greenland, on an open, flat plain facing directly onto the Arctic Ocean. Today, drift ice forms a continuous cover from the land here.
Astrid Lyså says that such old beach formations require that the sea all the way to the North Pole was periodically ice free for a long time.
”This stands in sharp contrast to the present-day situation where only ridges piled up by pack ice are being formed,” she says.
However, the scientists are very careful about drawing parallels with the present-day trend in the Arctic Ocean where the cover of sea ice seems to be decreasing.
“Changes that took place 6000-7000 years ago were controlled by other climatic forces than those which seem to dominate today,” Astrid Lyså believes.
Inuit immigration
The mapping at 82 degrees North took place in summer 2007 as part of the LongTerm project, a sub-project of the major International Polar Year project, SciencePub. The scientists also studied ruined settlements dating from the first Inuit immigration to these desolate coasts.
The first people from Alaska and Canada, called the Independence I Culture, travelled north-east as far as they could go on land as long ago as 4000-4500 years ago. The scientists have found out that drift ice had formed on the sea again in this period, which was essential for the Inuit in connection with their hunting. No beach ridges have been formed since then.
”Seals and driftwood were absolutely vital if they were to survive. They needed seals for food and clothing, and driftwood for fuel when the temperature crept towards minus 50 degrees. For us, it is inconceivable and extremely impressive,” says Eiliv Larsen, the NGU scientist and geologist.
(hat tip to many commenters and emailers, too numerous to mention, but thanks to all)
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moptop (14:25:51) :
Some geologists claim we have, it looks like Leif has picked up on that.
Others report highly localized spikes that produce highly localized disasters, i.e. fish boats floating over a methane release essentially fall into the bubble and sink.
http://dsc.discovery.com/news/afp/20031020/methane.html
The original question was about 4000 years ago, when the Arctic was warmer than today. Why wasn’t the methane released then?
No answer to this question except one that posited that all of the methane was trapped there during the Holocene since then, which is ridiculous. It is almost as if commenters are making it up as they go along.
It will have to get a LOT warmer for this time bomb to go off and this catastrophic feedback event has to be filed under “extremely unlikely”, along with large comet strikes, Betelguese (yeah, I probably spelled that wrong) going supernova, gamma ray bursts in the celestial neighboryhood, attack by an extraterrestrial civilization, the kind of risks we all have to live with as members of the human race that can’t be assigned a probability of zero.
moptop (15:40:00) :
The original question was about 4000 years ago, when the Arctic was warmer than today. Why wasn’t the methane released then?
I think the point was that it was warmer 6000-7000 years ago, and cold 4000 years ago, but we can just correct your 4000 to 6500 and continue from there.
Your own quote said:
“Underground stores of methane are important because scientists believe their sudden release has in the past been responsible for rapid increases in global temperatures”
So, it has happened [assuming that your quote is meaningful] so it was at such times warm enough [and therefore can be again].
Second, building up organic material in the Arctic is a slow process, 6500 years ago there may not have been much buildup yet.
Third, perhaps the temperature 6500 years was just not high enough [maybe that one tenth of a degree to small], but as Al Gore will lecture you, THIS time it will be, so repent.
It looks to me that your real argument is that because the methane was not released, it was not warm 6500 years ago.
I didn’t read all the 170 posts up to this point, so someone may have made the observation I am now making:
A raised beach on Greenland could just as well be caused by post glacial rebound of the crust (readjustment from the removal of ice load), which for instance in Stockholm amounts to an uplift of some 10 mm per year at present. I don’t know the rate of uplift in Greenland but it must have been, and probably still is, very significant. At the rate of the Stockholm uplift, 7000 years would cause a Holocene beach deposit to be raised by some 70 meters. On the other hand I cannot imagine that the NGU geologists wouldn’t have accounted for that.