Number 228 (Story #1), May 31, 1995 by Phillip F. Schewe and Ben Stein|
HIGHER-THAN-EXPECTED ARCTIC OCEAN TEMPERATURES were reported at this week's meeting of the Acoustical Society of America in Washington, DC. Applying the same acoustic technique for measuring water temperature as the recent Heard Island experiment, a US- Russian team broadcast 50-Hz sound waves in a 2600-km underwater path across the Arctic Ocean. Since the speed of sound through seawater varies with temperature, measurements of transit times can be used to calculate the water temperature. At the ASA meeting, Peter Mikhalevsky of Science Applications International Corporation in McLean, Virginia (703-243- 0643) reported that the sound waves took 1-2 seconds less than an estimated value based on tests conducted in the late 1970s and early 1980s. The team concluded that the temperature of the Arctic Ocean since that time has increased by 0.2-0.4 degrees Celsius at ocean depths of 200-700 meters, a calculation consistent with short-range measurements made from icebreakers last year. It's unknown whether the increased temperatures reflect long-scale global warming or simply represent cyclical variations over decades, but continuous monitoring of Arctic Ocean temperature could bring better insights into the question, as would sound data taken over many different paths in order to build up a 3-D temperature map of the ocean.