Scientists who sampled old ice deep in a Greenland glacier have found evidence that the amount of sulfate compounds in the atmosphere has tripled since the early 1900s and that the nitrate concentration has doubled. It, however, only began increasing around 1955.
Because the chemicals turn water vapor acidic and both are produced by burning fossil fuels, the findings lend further support to the belief that today's acid rain and acid snow problems can be traced to human activities that have intensified in this century.
Greenland glaciers are made from accumulations of snow that compress snowfalls from previous years into solid ice. Some of the glaciers have layers of snow dating back thousands of years. The new analysis was based on a core of ice 230 feet long. At the bottom of the core was compressed snow that fell in 1869.
The oldest layers of ice show relatively steady levels of nitrates and sulfates through the early decades of the span. The sulfate measurements show a sudden increase between 1900 and 1910, which then stayed steady until 1940. It then began increasing gradually until about 1960, when it began rising sharply until 1968. Then it steadied until 1984, the last year tested.
The findings, made by a team of United States and Danish scientists led by P.A. Mayewski of the University of New Hampshire, were published in last week's Science.