Glaciers respond directly and quickly to atmospheric conditions. As temperatures warm, summer melting increases. However, accumulation of ice in the winter also increases due to more snowfall. Air temperature tends to play the dominant role – there’s a strong statistical correlation between air temperature and glacier fluctuations over large distances (Greene 2005). Generally, when air temperatures warm, glaciers recede.
Consequently, because they’re so sensitive to changes in temperature, glaciers provide clues about the effects of global warming. Glacier mass balance is measured through a variety of techniques. Direct glaciological methods include ablation stakes, snow pits and snow probing. This data is then combined with independent geodetic surveys, collected and published by the World Glacier Monitoring Service (WGMS).
What do these glacier observations reveal? The following table shows the mass balance of individual glaciers over 2002 and 2003. Negative values indicate shrinkage. We see that there are isolated glaciers that are growing. However, focusing solely on these few glaciers to indicate global glacier growth paints a very misleading picture. The vast majority of glaciers are receding. And importantly, the shrinking trend is increasing (eg – 77% in 2002, 94% in 2003).
Glacier Mass Balance over 2002 (blue) and 2003 (red). (WGMS)