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Thursday, October 12, 2006

Bridge closed early
I'm always interested in archaeology and paleontology from the old country, so, naturally, this story caught my eye.

Scientists have found new evidence that the Bering Strait near Alaska flooded into the Arctic Ocean about 11,000 years ago, about 1,000 years earlier than widely believed, closing off the land bridge thought to be the major route for human migration from Asia to the Americas.

The story is quite simple really. The Woods Hole Oceanographic Institution drew some sea floor cores from the Chukchi Sea on the north side of the Bering Strait in 2002. They are just now examining them in detail. The result was that they found more sediment than they expected, leading them to believe that the area has been underwater longer that previously believed. Establishing the date when the Bering Strait flooded is important to understanding a number interesting problems, including climate change at the end of the last ice age and the migration of humans into the New World.

The Bering Strait is in an area that changes dramatically during the ice age cycles. For one thing, the Strait is not a gap between two continental plates as you would expect from a casual glance at the map. The North American and Asian continental plates are sutured together over a thousand miles west of the Strait at the Verkhoyansk Mountains. The Bering Strait is merely a wide, flat lowland at near sea level. Depending where sea level is that millennium the Strait might or might not be under water. For the last two million years it has been more often dry than wet there.

When dry, the land is not a narrow isthmus a some expect, but rather a wide sub-continent that separates the Pacific and Arctic Oceans with about a thousand miles of land. During an ice age the land between the Verkhoyansk Mountains and the edge of the ice sheet in Canada (approximately where the MacKenzie River flows today) was a separate ecological province that paleontologists call Beringia. This was the main zone of the woolly mammoth steppe.

Understanding the ecological and climatological history of Beringia has been very slow in coming. The region is not only remote, thinly populated, and difficult to work in because of the extreme climate, but for most of the twentieth century large swaths of it were off limits because of the Cold War and communication between scientists on opposite sides of the Strait was restricted by their respective governments. The situation has improved a little since the end of the Cold War. Communication and cooperation between scientists is much easier, but permission and transportation for outsiders to work in the Russian northeast are still difficult to obtain.

What will establishing that the Bering Strait flooded earlier mean? I don't expect it to change much in the argument over human migration into the new world. There were indisputably people in Alaska before the new date. The more interesting result will probably be in reconstructing the climatological history of the region. Opening and closing the Bering Strait has a huge effect on how the Arctic Ocean works. It changes the circulation of the Arctic Ocean, its salinity, and the heat transfer between the Arctic Ocean and the rest of the world's seas.

I expect to see a tiny flurry of activity as scientists comb through old evidence to see if anything confirms or refutes the conclusion that the Bering Strait was open sooner. If confirmed, then the students of historical climatology will need to revise their models. This might even have a small impact on how we model future changes due to global warming in the region. This should be fun.

Update: Spelling corrected so Elayne will still love me.

posted by John at 10:23 AM |