Polar Ice Caps

Scientists believe the growth of polar ice caps can be triggered by a combination of several global climactic factors. The major element is a small drop (perhaps no more than 15°F [9°C]) in average world temperatures. The factors that cause this drop can be very complex. They include reductions in incoming solar radiation, reflection of that energy back into space, fluctuations in atmospheric and oceanic carbon dioxide and methane levels, increased amounts of dust in the atmosphere such as that resulting from volcanic activity, heightened winds—especially in equatorial areas—and changes in thermohaline circulation of the ocean. The Milankovitch theory of glacial cycles also cites as factors small variations in the earth's orbital path around the sun, which in the long term could influence the expansion and contraction of the polar ice caps. Computer models based on the Milankovitch theory correlate fairly closely with observed behavior of glaciation over the past 600 million years.

Scientists use material preserved in the polar ice caps to chart these changes in global glaciation. By measuring the relationship of different oxygen isotopes preserved in ice cores, they have determined both the mean temperature and the amount of dust in the atmosphere in these latitudes during the recent ice ages. Single events, such as volcanic eruptions and variations in solar activity and sea level, are also recorded in polar ice. These records are valuable not only for the information they provide about past glacial periods; they serve as a standard to compare against the records of more modern periods. Detailed examination of ice cores from the polar regions has shown that the rate of change in Earth's climate may be much greater that previously thought. The data reflect large climatic changes occurring in periods of less than a decade during previous glacial cycles.

Scientists also use satellites to study the thickness and movements of the polar ice caps. Information is collected through radar, microwave, and even laser instruments mounted on a number of orbiting satellites. Scientists have also utilized similar technology to confirm the existence of polar ice caps on the Moon and Mars. These relict accumulations are indicative of the history of these bodies and may prove useful in future exploration efforts as a water and fuel source. The detailed and frequent observations provided by the space-based tools permit scientists to monitor changes in the ice caps to a degree not possible by previous land-based methods.

Recent findings suggest that the ice sheets may be changing much more rapidly than previously suspected. Portions of the ice sheets in Greenland, West Antarctica, and the Antarctic Peninsula are rapidly thinning and, more importantly, losing mass. Scientists are able to document modifications of ice accumulations rates, volume of melt water, and the impact of elevated seawater temperature and utilize this information in characterizing the movement and evolution of these ice sheets. Glaciers flowing to the ocean in these areas appear to be accelerating in their advance. Although this acceleration may not be directly related global warming, the potential for their combined impact on sea level is of concern for many observers.

Predicting the future of the ice caps is a difficult task. It is complicated by the interactions of the various factors that control the ice. One example is the possibility that the warming climate will reduce the areal extent of ice in the polar regions. This will decrease the albedo, or tendency to reflect incoming solar radiation, of the polar regions. White ice is particularly good at reflecting much of the sunlight that reaches it and this has a cooling effect on the overall climate. With less albedo, the climate will tend to warm even more. However, the melting ice could impact the thermohaline circulation of the oceans, paradoxically resulting in extensive cooling. These seemingly contradictory results can only be resolved through more detailed scientific observation.

The process of global warming and other forces of climate change will continue to be reflected in the ice caps. Should global warming continue unchecked, scientists warn, it could have a drastic effect on polar ice. Small variations over a short period of time could shrink the caps and raise world sea levels. Even a small rise in sea level could affect a large percentage of the world's population, and it could significantly impact major cities like New York. Ironically, global warming could also delay or offset the effects of the coming ice age.