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North America's wind patterns shifted in past 30,000 years DARTMOUTH COLLEGE NEWS RELEASE Posted: January 23, 2007 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 deg 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." Feng explains that global climate change is often manifested by changes in general atmospheric circulation, i.e. winds, and this results in changing temperature and precipitation patterns. Clues of past climates usually hint at temperature and precipitation changes, but this is the first time that changing continental wind patterns have been reconstructed. The researchers gathered their evidence using oxygen and hydrogen isotopic compositions of cellulose extracted from ancient wood. Feng and her team interpret the historic prevailing easterlies to be a result of a growing and intensifying northern circumpolar vortex, which was influenced by the powerful Laurentide Ice Sheet, an enormous mass of ice that covered a great deal of northern North America. Under this circulation regime, the jet stream shifted southward, and as a result, the Pacific Northwest received much less marine moisture from the Pacific. This is consistent with earlier studies of vegetation in the Pacific Northwest, indicating that the region was significantly drier during the last glaciation. "This study is likely to open up new avenues of research based on oxygen and hydrogen isotopes in old wood," says Feng. "Climate change involves interactions among temperature, precipitation, and wind, but until now research has rarely been able to observe or confirm prehistoric winds and their continental-scale patterns. In the future, studies using this methodology will be able to look into ancient climates through a new window, and test hypotheses about climate change mechanisms. Such studies can potentially lead to more realistic formulations of future climate scenarios and better evaluations of their plausibility." In addition to Xiahong Feng, who also holds the Frederick Hall Professorship in Mineralogy and Geology at Dartmouth, other authors on the paper include: Allison L. Reddington, a member of the Dartmouth Class of 2004; Anthony M. Faiia, Dartmouth research associate; Eric S. Posmentier, adjunct professor of earth sciences at Dartmouth; Yong Shu, Dartmouth PhD candidate; and Xiaomei Xu, from the Earth System Science Department at the University of California, Irvine. "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." |
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Skylab, America's first space station, began with crippling problems created by an incident during its May 1973 launch. High temperatures and low power conditions aboard the orbital workshop forced engineers to devise corrective measures quickly. Astronauts Pete Conrad, Paul Weitz and Joe Kerwin flew to the station and implemented the repairs, rescuing the spacecraft's mission. This film tells the story of Skylab's first 40 days in space.
NASA's New Horizons space probe will fly past Jupiter in late February, using the giant planet's gravity as a sling-shot to bend the craft's trajectory and accelerate toward Pluto and the Kuiper Belt. Mission officials describe the science to be collected during the Jupiter encounter during this briefing.
The 24th Russian Progress resupply ship sent to the International Space Station successfully makes the final approach and docking to the Pirs module of the outpost while running on automated controls.
Barbara Morgan, the former Idaho school teacher who served as Christa McAuliffe's backup for the Teacher in Space program, sits down for this NASA interview. As NASA's first Educator Astronaut, Morgan will be a mission specialist and robot arm operator during shuttle Endeavour's STS-118 flight to the space station, targeted for launch in June.
On October 3, 1962, Wally Schirra became the fifth American to rocket into space. This NASA film entitled "The Flight of Sigma 7" explains the 9-hour voyage that gained important knowledge in the Mercury program.
The Russian Progress M-57 cargo vessel undocks from the International Space Station on January 16 for re-entry into the atmosphere. It was the 22nd resupply ship sent to ISS.
The fourth servicing mission to the Hubble Space Telescope extended the craft's scientific potential with an advanced camera and performed a major overhaul on the orbiting observatory's power system with the installation of new solar arrays and an electrical heart. The crew of space shuttle Columbia's STS-109 mission tell the story of the March 2002 mission in this post-flight highlights film.