A newish pollen study on the Bering Land Bridge (BLB) hit my desk this week, published in the journal Arctic, Antarctic, and Alpine Research. It suggests that the first people to populate North America didn't leave the BLB because of climate change.
The Bering Land Bridge is the name for the now-submerged land mass that connected Siberia to North America between about 60,000 and 11,000 years ago. Most studies of the dating of the population of the American continents hinge on what happened to that bridge, including the questions of when people first entered it, and when people left it to enter North America.
A pollen core was taken from the Norton Sound (20 meters above the BLB) and radiocarbon dated. According to this particular core, between 29,500 and 11,500 RCYBP, the Bering Land Bridge had an arid, cool climate with grass-herb-willow tundra. At about 11,500 RCYBP, when the water began to rise, the pollen shows a wetter climate with deeper snows and moist, cool summers.
One theory for the population of North America involves people leaving the BLB because the weather got crummy between 21,000 and 18,000 years BP, at the end of the Last Glacial Maximum. This new study seems to suggest that, at least at the point of the sediment core, that deterioration didn't happen until 10,000 years later or so. People could still have left that early, it just doesn't appear to have been because of climate change. Bearing in mind, of course, that this is just one sediment core, the questions still remain.
Ager, Thomas A. and R. L. Phillips 2008 Pollen evidence for late Pleistocene Bering land bridge environments from Norton Sound, northeastern Bering Sea, Alaska. Arctic, Antarctic, and Alpine Research 40(3):451–461.
Sunrise on the Bering Sea. Photo by ra64
Comments
Thanks for posting! Keep up the great work.
Very Interesting. I am a former teacher in Savoonga. It would be most interesting to know what other sites were measured. The area is larger than most realize and there are many climatic differences. What is evident near Nome is often much different than Savoonga or more northern areas.
This is probably the wrong place for this, but one often overlooked cause of the Arctic melt is the increasing salinity of the Mediterranean over recent years. The Aswan Dam stopped the flow of fresh water into the Eastern Med and reduced flow from the other great rivers, the Rhone, Ebro etc has pushed up the sality layer which creeps out into the Atlantic. This now takes 6km to dissolve into the Atlantic instead of 4km and be taken up by the Gulf Stream, which in turn is causing the icebergs to melt from the bottom, as described by the locals in the National Geographic. A study was first puiblished in 1989 and the two solution made were a dam or membrane curtain across the Straits of Gibraltar. Here in another reference.
http://www.toptotop.org/climate/salinity.php
MD