Climate Fact: Three Glaciers and the Pacific Decadal Oscillation
Most of the West’s water ultimately comes from ice (snowpack/glaciers) and changes in this ice can have stark impacts on streamflow. For example, in North Cascades National Park, where there is now 40 percent less glacial mass than there was in 1850, Lewis Glacier disappeared in 1990. Streamflow in the watershed it fed subsequently declined by 40 percent. An analysis of three glaciers, Wolverine Glacier on Alaska’s Kenai Peninsula, Gulkana Glacier in Alaska’s interior and South Cascade Glacier in Washington State, indicate that since 1989 all three glaciers have been losing mass at previously unseen rates, a trend that corresponds to contemporaneous increases in temperatures and decreases in precipitation throughout the West. Prior to 1989, the Pacific Decadal Oscillation (PDO), the periodic shift in North Pacific sea-surface temperature distributions, was the primary cause of glacial mass variability. “Warm” PDO phases shift winter storm tracks north, causing more winter snow to fall on Wolverine Glacier in Alaska (resulting in glacial growth) and less to fall on South Cascade Glacier (resulting in glacial shrinkage). “Cool” PDO phases had the opposite effect. Gulkana Glacier is less affected by maritime influences and thus does not show a distinctive response to PDO phases.
Seasons: Spring, Summer, Fall
Sources: United States Geologic Survey. “Fifty-Year Record of Glacier Change Reveals Shifting Climate in the Pacific Northwest and Alaska, USA.” 6 July 2009. Accessed Online 7 August 2009
