Melting of Glaciers and Ice Sheets
One of the most pronounced effects of climate change has been melting of masses of ice around the world. Glaciers and ice sheets are large, slow-moving assemblages of ice that cover about 10% of the world's land area and exist on every continent except Australia. They are the world's largest reservoir of fresh water, holding approximately 75% (1).
Over the past century, most of the world's mountain glaciers and the ice sheets in both Greenland and Antarctica have lost mass. Retreat of this ice occurs when the mass balance (the difference between accumulation of ice in the winter versus ablation or melting in the summer) is negative such that more ice melts each year than is replaced (2). By affecting the temperature and precipitation of a particular area, both of which are key factors in the ability of a glacier to replenish its volume of ice, climate change affects the mass balance of glaciers and ice sheets. When the temperature exceeds a particular level or warm temperatures last for a long enough period, and/or there is insufficient precipitation, glaciers and ice sheets will lose mass.
One of the best-documented examples of glacial retreat has been on Mount Kilimanjaro in Africa. It is the tallest peak on the continent, and so, despite being located in the tropics, it is high enough so that glacial ice has been present for at least many centuries. However, over the past century, the volume of Mount Kilimanjaro's glacial ice has decreased by about 80% (3). If this rate of loss continues, its glaciers will likely disappear within the next decade (4). Similar glacial meltbacks are occurring in Alaska, the Himalayas, and the Andes.
As CO2 emissions and climate change continue, risks to the health of the ocean will become a more prominent concern. With accelerated melting back of glaciers and ice sheets and the subsequent rise in sea level, with further decreases in oceanic pH, and with deceleration of the thermohaline circulation, there are many ways in which the delicate balance of ocean dynamics and ecosystems are being put at risk. These factors, combined with the uncertainty in predicting exactly how these impacts will interact, are causing changes in the ocean: an increasingly problematic issue for future generations