Antarctica and Greenland, the two large ice sheets, represent some of the most bleak and hostile places on Earth. Not many geoscientists have the mettle to explore these remote places, but they remain one of the essential frontiers for research. These large and thick ice sheets look relatively homogeneous compared to other parts of the planet, but in fact, their behavior is not completely understood. The fact remains that if the ice sheets on Antarctica and Greenland were to melt, a feat that cannot happen over decades or even centennial time scales, don't worry, global sea level would rise by about 70 meters which would drown most coastal cities such as New York, Shanghai, Mumbai, and Jakarta. Just this threat should cause global leaders to stay up at night, though!
Ice is the frozen segment of the atmospheric moisture cycle. As you will remember from the discussions of Snowball Earth and the Pleistocene ice ages in Module 1, it is a very important component of Earth’s climate system — ice is the most reflective material on the surface, and as such it can exert an important control on how much sunlight the Earth absorbs, which directly affects the Earth’s temperature.
Ice is also an important and highly sensitive indicator of climate change in the polar regions and in areas of high altitude where mountain glaciers occur. Glaciers will grow or shrink in response to changes in temperature and precipitation. The temperature response is pretty obvious — glaciers melt as the temperature rises. The precipitation response is perhaps less obvious, but glaciers can expand if winter precipitation increases, and they shrink if the winter precipitation decreases. Just as the ground temperatures respond somewhat sluggishly to surface temperature changes, glaciers respond sluggishly to climate changes, which is good in the sense that they give us a better sense of the important trends in climate change that might otherwise be obscured by short-term variations. In the following pages we discuss the key different types of ice and how it is changing: glaciers in mountainous regions, sea ice in the Arctic, and the large Antarctic and Greenland ice sheets.