Regional Climate: Current Research

Determining 20th Century Trends in Pacific Northwest Snowpack



Low- to moderate-elevation snow is both an important source of summer water and a sensitive indicator of climate change in the Pacific Northwest (PNW). A preliminary study (Mote 2003) showed substantial elevation-dependent declines in PNW snowpack, indicating that regional warming is already reducing water supply (figure 1). Continued research in this area will further define trends in snow water equivalent in the PNW and western U.S.

Research Questions

We use statistical approaches and simulations with the VIC hydrology model to address these questions.

Map of the Pacific Northwest region of the United States, highlighting the Columbia River Basin

Figure 1 Trends in April 1 snow water equivalent based on data from 260 snow course collections sites. Most stations show a decline in snow water equivalent. The fact that trends are highest at low elevation sites implicates warming as a cause of the trend.

Related Work

Climate Impacts Group (CIG) research on trends in 20th century temperature and precipitation in the PNW finds that average annual PNW temperature increased 0.7°C-0.9°C (1.3°F-1.6°F) between 1930-1995 (Mote 2003). Precipitation during this period increased 13%-38% (1930-1995) depending on the climatic zone (Mote 2003). The CIG is also characterizing variability and trends observed in 20th century PNW streamflow.

Selected References

For more publications on climate impacts on PNW climate, please see CIG Publications.

Mote, P. W. 2003. Trends in temperature and precipitation in the Pacific Northwest during the twentieth century. Northwest Science 77(4): 271-282.

Mote, P.W. 2003. Trends in snow water equivalent in the Pacific Northwest and their climatic causes. Geophysics Research Letters 30: DOI:10.1029/2003GL017258.