Suspect gases used to trace ocean currents

Press, 10 February 1982, Page 20

Suspect gases used to trace ocean currents

Bv

RALPH KAZARIAN

of the National Science Foundation, Washington, D.C.

The same gases that made headlines in the 1970 s when it was feared they might deplete a protective layer oi ozone in the upper atinoshphere now have been found in the world's oceans, giving scientists a new tool with which to study ocean circulation.

Finding the gases - chlorofluorocarbons — in the oceans also will enable scientists to determine the rate at which similar man-made pollutants can be absorbed into the ocean basins, the National Science Foundation of the United States reports.

Chlorofluorocarbons — produced by about 25 manufacturers throughout the world — are the gases used in refrigerators. They have been banned as propellants in such products as hair spray and shaving cream. They attracted wide attention when it was, reported that fluorocarbons from spay cans may rise into a region of the upper atmosphere called the ozone layer — between 11 and 48 kilometres above the earth - and touch off a chain reaction that could deplete the laver. Ozone is a highly reactive form of oxvgen. an important part of the air we breathe. It exists inf verv small amounts throughout the atmosphere and

is concentrated mainly in the ozone layer which screens out much of the sun's destructive ultraviolet radiation. Scientists feared that the depletion of the ozone layer would increase the incidence of skin cancer and possibly endanger some forms of plant life.

Now chlorofluorocarbons can play a more constructive role by ’ giving oceanographers information about how it circulates in the oceans and how long such circulation takes. Oceanographers need this information to calibrate and verify models of ocean circulation which are cruical in determining global weather and climate patterns. By studying the rate at which chlorofluorocarbons sink to the ocean bottom, scientists also can determine how fast the world's oceans can absorb similar man-made pollutants.

For three decades man has inadvertently dumped into the oceans chemicals which can be used to trace global circulation patterns. One. that has been used most extensively is tritium. produced in large doses by the nuclear weapons testing of the late 1950 s and early 19605. Tritium injected into the atmosphere ' during the weapons' testing eventually entered the ocean.

Until now. ocean scientists have exploited tritium as one of the tracers of ocean mixing and circulation. However, tritium, which is radioactive, loses its effectiveness because it decays and some researchers fear that they have only a dozen or so -more years in which they can use that element as a’tracer. On the other hand, any chlorofluorcarbon is very inert in the atmoshphere and the oceans, which means it is not readily destroyed by chemical or radioactive decay processes. It is expected to be a useful tracer in the oceans for decades.

Working in the North-West Atlantic on a programme called Transient Tracers in the Ocean — funded jointly by the N.S.F. and the. United States Department of Energy — Dr Richard H. Gamnion of the University of Washington in Seattle tested techniques to enable oceanographers to switch their tracer from tritium to chlorofluorocarbons. Dr Joel D. Cline of the National Oceanic and Atmospheric Administration (N.0.A.A.) . and Dr Gammon 'developed the technique after two years of work funded by N.O.A.A. Tiiis project led to the discovery of chlorofluorocarbons in the Pacific Ocean. * I