What has research proven?
We have measured the mass balance on ten glaciers in the North Cascades each year since 1984. The cumulative mass loss has been substantial. Annual mass balance is the most sensitive annual glacier climate indicator. North Cascade glaciers annual balance has averaged -0.51 m/a of water equivalent from 1984-2010 a cumulative loss of over 13.25m in glacier thickness. This represents a net loss of ice thickness exceeding 14 m or 20-40 % of their total volume since 1984 due to negative mass balances. The trend in mass balance is becoming more negative which is fueling more glacier retreat and thinning note figure at right. The map at right indicates the location of the glaciers (green circles) where we monitor annual glacier mass balance.
The annual glacier mass balance record below indicates that the response of annual balance is quite similar for each glacier. This demonstrates that it is regional climate changes from year to year that control glacier mass balance, not local microclimates. The cause of the negative mass balances has primarily been temperature rise. Precipitation has increased during the last 25 years. However, snowpack has not indicating more winter rain and melt events.
The data indicate broad regional continuity in glacial response to climate. Cross correlation values of annual balance between glaciers ranged from 0.73 to 0.98. The record reflects less variability and a more negative trend from 1984-1995. Since 1996, there has been increasing inter-annual variability with alternately extreme positive and negative years, with a dominantly negative trend. The annual balance of individual glacier is in a Table below The chart at right shows the annual balance of each glacier and how they are closely correlated, following the same trend from year to year, but do have a significant range in annual balance during each given year.