|Speaker:||Karl A. Erb, Director, Office of Polar Programs, National Science Foundation|
|Topic:||“Science at the Earth's Poles”|
President-Elect Ken Haapala called the 2143rd meeting to order at 8:15 p.m. on March 8, 2002. The Recording Secretary read the minutes of the 2142nd meeting and they were approved.
The speaker for the evening was Karl A. Erb, Director, Office of Polar Programs, National Science Foundation. The title of his presentation was “Science at the Earth's Poles”.
The Polar Research Program of the National Science Foundation is conducted in Antarctica, and the Arctic Ocean and surrounding landmasses including Alaska, Greenland, and Siberia. This program can be discussed in three broad areas (1) ice, earth and climate, (2) life in the cold and dark, and (3) the origins of the universe. The landmass of Antarctica is approximately the size of the United States plus Mexico. However, seasonal expansion of the sea ice shelfsurrounding pack ice can essentially double the size of the ice-covered area. The average depth of the continental ice sheet is 2.2 km and is as deep as 4.8 km.
Ice core samples from the Greenland ice sheet contain, along with the seasonal banding, dark bands corresponding to volcanic eruptions that help calibrate the dating of the individual bands. Within these bands the O16/O18 ratio can be used to deduce the average surface temperature at time of deposition, and the identification of pollen grains can indicate the average prevailing winds. Distinct signals have been seen in these indicators for the Medieval Warm Period and for the Little Ice Age that followed in the period from 1645 to 1715. About 15,000 years ago, the average temperature went from -45°C to -25°C within a decade and persisted for a century. Ice cores from the Antarctic ice sheet near Vostok Station, at an elevation of 13,000 ft, indicate that in the most recent geological period warm episodes lasting 10,000 to 15,000 years recur approximately every 100,000 years. This periodicity has been explained by changes in certain orbital characteristics of the earth.
Research in Antarctica is also probing the stability of the West Antarctic ice sheet. The amount of ice in this sheet has diminished greatly since the last glacial maximum 22,000 years ago. It appears to have been relatively stable over the last 3,000 years, but if it were to melt, it would raise sea levels by approximately 5 meters.
The Arctic Ocean is locked in ice throughout much of the year. The ice thickness has decreased by over 30% in the last 20 years, and its area has decreased substantially. The NSF-supported SHEBA program measures the transmission and reflection of solar energy by the Arctic atmosphere, clouds, sea ice, and ocean to help predict climatic effects. New observations are being made to measure the energy flux from the sea ice and melt ponds on the ice surface that change the albedo of the surface. Submarine explorations that revealed the decrease in Arctic sea ice thickness also mapped regions of the Arctic Ocean floor for the first time and identified features subsequently shown to be “smokers” and other thermal vents.
One of the most dramatic discoveries in Antarctica in the last decade was Lake Vostok, a liquid water lake under 3750 m of ice. Its existence was verifieddetected by radar that passes through ice, but is reflected by water. The liquid water of the lake is as much as 1000 m thick. It is thought to be at least 400,000 years old, and perhaps as much as 15 M years old. This is intriguing because bacteria in the lake would have been isolated from the atmosphere for at least that period. Core drilling to within 150 of the ice-water boundary has shown that the ice above the water appears to be accreted frozen lake water, and contains bacteria spores. Recent studies in Antarctica have found bacteria metabolizing at temperatures well below freezing. Penetration to sample the water will not be attempted until contamination of the lake can be prevented.
Telescopes in Antarctica have an advantage in that they look through a very cold and extremely low humidity atmosphere. Balloon telescopes can be launched to circle the continent on prevailing circumpolar winds. The South Pole microwave telescopes are located at an altitude of 10,000 ft. These telescopes have been used to look for temperature variations in the big bang background radiation. Last year the Degree Angular Scale Inferometer (DASI) Telescope showed that the universe is flat; no relativistic curvature could be detected. From this and other data, astrophysicistswe now conjecture that the universe is composed of 5% ordinary matter, 35% “dark matter” and 60% “dark energy”.
The Antarctic Muon and Neutrino Detector Array (AMANDA) is a “telescope” that sits in the ice sheet and looks through the earth. It looks for neutrinos that pass through the earth then generate muons in the ice that are detected by their Cherenkov radiation. Underwater versions of the detector array have problems with bioluminescent interference and inherent instabilities that the array embedded in ice does not. Neutrinos are relatively unabsorbed by the interstellar medium, so have the potential to bring us information about distant objects in the universe that are invisible to electromagnetic probes.
Mr. Erb kindly answered questions from the floor. President-Elect Haapala thanked Mr. Erb for the society, and welcomed him to its membership.
The President-Elect then introduced Mr. William Saalbach, Program Chair, who briefly addressed the Society on a report in the March 8 issue of Science. R. P. Taleyarkhan of the Oak Ridge National Laboratory and others report evidence for tritium and excess neutron emissions produced by sonoluminescence in deuterated acetone. Cavitation in the supercritical phase was seeded by neutrons. These authors did not observe tritium and excess neutron emissions when normal, undeuterated acetone was used. A separate group of researchers at the same laboratory has reported that they could not replicate the neutron measurements, and the first group has posted a rebuttal. The disputed interpretation of this “bubble fusion” experiment has already drawn comparison with the “cold fusion” debate of a decade ago.
The President-Elect made the announcements about the next meeting, parking, and refreshments, and adjourned the 2143rd meeting to the social hour at 9:37 p.m.
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