Slide 15: Thermal indicators: Glacial melting
The change in size of glaciers is measured by their mass balance: the net annual gain/loss of mass at the glacier surface per unit surface area.
This is useful because as well as monitoring glacier size, it measures the contribution of glacial melt to sea level rise.
The world glacier monitoring service has shown that almost all glaciers worldwide are retreating. (IAHS (ICSI)/UNEP/UNESCO, 1998)
A few glaciers in Norway and New Zealand are actually advancing, but this is because of increased precipitation due to warmer weather.
Exposure of radiocarbon-dated ancient remains in high saddles in the Alps shows recession is reaching levels not seen for thousands of years
This ice has not melted for thousands of years, hence the finding of the 5000 year-old Oetzal "ice man". (IPCC, 2001)
The pictures on the left show the retreat of the Grinnell glacier over a 98 year period in Montana's Glacier National park in the United States. By examining and dating the glacial moraines of various glaciers, a comprehensive picture of their movements can be obtained, in this case the accelerating recession of the Gangotri glacier.
Furthermore, the final graph details the decreasing net balance for both 30 monitored glaciers and the means of glaciers in 30 different regions monitored by the World Glacier Monitoring Service.
IPCC (2001): Climate Change 2001: The Scientific Basis. (Houghton, J.T., Ding, Y., Griggs, D.J., Noguer, M., van der Linden, P., Dai, X., Maskell, K. and Johnson, C.A., Eds.). Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press.
IAHS(ICSI)/UNEP/UNESCO, 1998: Fluctuations of the Glaciers, 1990-95. W. Haeberli, M. Hoelzle, S. Suter and R. Frauenfelder (eds.), World Glacier Monitoring Service, University and ETH, Zurich.