Relationships between interannual variability of glacier mass balance and climate

The interannual variability of glacier mass balance is expressed by the sta ndard deviation of net balance, which varies from about +/-0.1 to +/-1.4 m a(-1) for a sample of 115 glaciers with at least 5 years of record. The sta ndard deviation of net: balance is strongly correlated with the mass-balanc e amplitude (half the difference between winter and summer balances) for 60 glaciers, so the amplitude can be estimated from net balance standard devi ation for the other 55 glaciers where winter and summer balances are unavai lable. The observed and calculated mass-balance amplitudes for the 115 glac iers show contrasts between the Arctic and lower latitudes, and between mar itime and continental regions. The interannual variability of mass balance means that balances must be measured for at least a few years to determine a statistically reliable mean balance for any glacier. The net balance of t he Greenland ice sheet is still not accurately known, but its standard devi ation is here estimated to be about +/-0.24 m a(-1), in agreement with othe r Arctic glaciers. Mass-balance variability of this magnitude implies that the ice sheet can thicken or thin hy several metres over 20-30 yeats withou t giving statistically significant evidence of non-zero balance under prese nt climate.