Wednesday, January 24, 2007

Well, this is interesting The winds of change
Dartmouth researchers have learned that the prevailing winds in the mid latitudes of North America, which now blow from the west, once blew from the east. They reached this conclusion by analyzing 14,000- to 30,000-year-old wood samples from areas in the mid-latitudes of North America (40-50�N), which represents the region north of Denver and Philadelphia and south of Winnipeg and Vancouver.

The researchers report their findings online on Jan. 23 in the journal Geology, published by the Geological Society of America.

"Today in the mid-latitude zone of North America, marine moisture is transported either from the west coast by westerly winds, or from both the west and east coasts by storms," says Xiahong Feng, the paper's lead author and a professor of earth sciences. "In this study, we found evidence that during the last glacial period, about 14-36 thousand years ago, the prevailing wind in this zone was easterly, and marine moisture came predominantly from the East Coast."

They argue that the Laurentide ice sheet shifted the jet stream south which. . .affected the wind direction somehow (the article doesn't say). It also doesn't say how they determined this except that it involved "oxygen and hydrogen isotopic compositions of cellulose extracted from ancient wood". One would guess there is some difference between Atlantic and Pacific/continental isotope compositions. Still, this would go a long way towards explaining climate change in these regions over time.

Also note this: "This study began as Allison Reddington's undergraduate honors thesis," says Feng. "This exemplifies the extraordinary opportunities that undergraduates at Dartmouth have to become integral parts of research groups." Good for undergrads!

And in other glacial news: Scientists observe drumlin beneath ice sheet
Scientists have discovered a warehouse-sized drumlin � a mound of sediment and rock � actively forming and growing under the ice sheet in Antarctica. Its discovery, and the rate at which it was formed, sheds new light on ice-sheet behaviour. This could have implications for predicting how ice sheets contribute to sea-level rise. The results are published this week in the journal Geology.

Drumlins are well known features of landscape scoured by past ice sheets and can be seen in Scotland and Northern England where they were formed during the last ice age. They form underneath the ice as it scrapes up soil and rock, and they slow down the rate at which the ice can flow.

Scientists from British Antarctic Survey (BAS), Swansea University and NASA's Jet Propulsion Laboratory Pasadena used a new technique of time-lapse seismic surveys to find the drumlin, and how it formed over time.

You can navigate a plane in south-central Wisconsin by the drumlins since they all trend in one direction. Growing up there, I always wondered why there were so many freakin' hills and it turned out I was living in the middle of a drumlin field.