Bart is one of many scientists studying the Antarctic ice sheet for clues that will help predict how the global sea level might change in the future. And because more than half the population of the United States lives within 50 miles of the coast, this information could be critical. A relatively high concentration of the O-18 isotope within the shells of marine organisms suggests a colder climate, Bart said. That's because the chemistry of water depends partly on temperature. When it's cold, more ice accumulates on land.
Marine organisms construct their shells out of elements in sea water.
That's been a typical pattern for most of the past 800,000 years - a rapid rise in sea level, then a gradual fall. The impression one gets is that we're at a peak, which is in contrast to what a lot of scientists who are concerned about global warming might say. Using these proxy records, the likelihood is that we're heading into another cold phase. Bart and other scientists studying glaciers in the Antarctic are presently attempting to make direct observations to confirm or disprove the proxy record. They are drilling cores from the ocean floor and are also taking seismic soundings under the sea.