Elwha Watershed Information Resource
Climate
Dam removal on the Elwha River is projected to benefit the majority of plant and animal species in the watershed (NPS 1996) and will likely change the microclimate of the Elwha River (for example, decreased water temperatures). However, biologists must also consider the impacts of global climate change (for example, temperature increases) on fish, wildlife, and vegetation. Warming will affect most plant and animal species in a negative way by altering habitats (Parmesan and Yohe 2003). Climate change in the Pacific Northwest is projected to increase temperatures, reduce snowpack, and increase drought occurrences (Mote and others 2003).
Climate is measured over the long term and is the average of weather over an extended period of time (a year, a decade, a century, or even longer). Several factors affect climate: latitude, altitude, prevailing wind, aspect, and distance from the ocean. Slight changes in climate (such as a change in temperature by only a few degrees) can affect the distribution of animal species (Schneider and Root 1998). The Elwha River Watershed (83 percent of which lies within the Olympic National Park boundary) has a moderate marine climate with mild and predominantly dry summers and wet winters with the majority of precipitation occurring between October and March.
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| Alpine area in upper Elwha headwaters. Betsy Carlson, National Park Service |
Climate Variations
Short-term variations (every 3-7 years) in the El Niño-Southern Oscillation (ENSO) create El Niño and La Niña events. El Niño events are generated by sea surface temperatures that are 4-6°F above average in the central Pacific Ocean (that is, the area between the International Date Line and the western part of South America). During an El Niño, winters in the Pacific Northwest tend to be drier and warmer than normal. The strongest 20th century El Niño event occurred in 1997-1998; other significant El Niño events occurred in 2002-2005. A La Niña event is essentially the opposite of an El Niño event. La Niña events occur when ocean surface temperatures are 2-5°F below average in the central Pacific Ocean. During a La Niña, winters in the Pacific Northwest are usually colder, wetter, and have above average snowfall. One of the strongest La Niña events in the Pacific Northwest occurred in the winter of 1999-2000 (December-February) with heavy snow and cool temperatures. For more information on ENSO events, visit the National Oceanic and Atmospheric Administration’s sites on El Niño and La Niña.
Long-term variations (20-30 years) in the Pacific Decadal Oscillation (PDO) create similar warm and cold phases like the ENSO events--but over a longer time period (Goodrich 2006). PDO changes are caused by fluctuating sea surface temperatures in the north-central Pacific Ocean as well as near the Gulf of Alaska. During years of a neutral ENSO (that is, years where there is neither an El Niño nor a La Niña event) and a cold PDO, winters in the Pacific Northwest are cooler and wetter than normal. During years of a neutral ENSO and a warm PDO, winters are warmer and drier than normal. Warm and cold PDO cycles that coincide with ENSO often reduce the effects of El Niño and La Niña events. Studies indicate the PDO has been in a warm phase since the late 1970s, but climate changes in the 1990s suggest the PDO may be switching to a cool phase (Mazza 1999).
Global variations due to climate change (that is, global warming) are attributed to the burning of fossil fuels over the last 200 years (Kessel 2000). Increases in greenhouse gases (such as carbon dioxide and methane) from fossil fuels have warmed the earth’s surface by trapping heat in the atmosphere. How much warming will occur from greenhouse gases in the future is unclear; however, temperature increases of only a few degrees can greatly alter habitats and impact the survival of plant and animal species (Parmesan and Yohe 2003; Williams, Jackson, and Kutzbach 2007).
Effects on the Pacific Northwest
Climate warming, El Niño, and a warm PDO phase all affect the Pacific Northwest’s fish, wildlife, plants and people by decreasing average annual snowpack, decreasing average salmon survival, decreasing average forest growth, and by increasing the risk of forest fires (Mote and others 2003).
Regional temperatures in the Pacific Northwest have increased by 1.5°F during the 20th century and scientists predict temperatures could increase another 2.7°F ) by 2020 (Mote and others 2003). Climate warming results in warmer ocean conditions and a reduction in the amount of snowpack (the accumulation of snow at higher elevations, such as mountains). The amount of snowpack determines how much water will melt and enter the rivers and streams.
Climate warming directly affects salmon and other animals by disturbing the upwelling of nutrients in the ocean, reducing stream flows, and increasing stream temperatures. Upwelling (that is, wind driven movement of nutrient rich cold water to the surface) in the ocean is important to the food chain. When upwelling is disrupted, plankton are affected, and they in turn affect the rest of the food chain--including juvenile salmon (Mazza 1999). If the snowpack is reduced, less water enters the rivers and streams, which results in lower flows and increased water temperatures. Water temperature influences every aspect of salmonid life history from migration timing and spawning to egg maturation and development (Groot and Margolis 1991; Groot, Margolis, and Clarke 1995). For example, Chinook salmon (Oncorhynchus tshawytscha) entering the Elwha River require cool water temperatures (below 57°F) to spawn (National Park Service 1996). Warm water temperatures can cause disease, increase pre-spawn mortality, and reduce egg production and survival of hatching salmon (Gilhousen 1990). Overall, in most instances warming temperature alter habitats and negatively affect plant and animal communities (Naiman, Decamps, and McClain 2005)
Due to climate warming, drought conditions can occur in the Pacific Northwest during years with low winter snowpack (due to low precipitation or above normal temperatures) and also in years with exceptionally dry summers. The summers of 2003 and 2004 were examples of extremely dry conditions, and in 2005 low snowpack resulted in drought conditions (NOAA 2005). Dry Northwest summers can cause great moisture deficits that affect forest growth by inhibiting seedling establishment and summer photosynthesis (Mote and others 2003). The warm temperatures can also increase disease and insect infestations in tress, and forest fires (Rapp 2004). Using models, scientists are predicting changes in forest growth, such as the spread of woody plants into grasslands and an increase in fire risk. Scientific models estimate an increase in fire season severity by 10-50 percent over most of North America (Flannigan, Stocks, and Wotton 2000). In the West, forest managers will have to try and reduce the risk of wild fires even as fuel loads (trees, under brush, and grasses) increase (Rapp 2004).
All of the climate variations (short and long term) impact the environment in the Elwha River Watershed, but climate warming poses the biggest threat. As researchers develop restoration plans for the Elwha, they will need to factor in climate warming. Additional steps in habitat restoration may need to be taken to offset the local effects of climate warming that will impact the Elwha River Watershed.
Reference
Flannigan, M. D., B. J. Stocks, and B. M. Wotton. 2000. "Climate change and forest fires." The Science of the Total Environment. Volume 262. Pages 221 to 229.
Gilhousen, P. 1990. "Prespawning mortalities of sockeye salmon in the Fraser River system and possible causal factors." International Pacific Salmon Fisheries Commission Bulletin. Volume 27. Vancouver, B.C.
Goodrich, G. B. 2006. "Influence of the Pacific decadal oscillation on winter precipitation and drought during years of neutral ENSO in the western United States." Weather and Forecasting. Volume 22, Number 1. Pages 116 to 124.
Groot, C., and L. Margolis. 1991. Pacific Salmon Life Histories. University of British Columbia Press. Vancouver, B.C.
Groot, C., L. Margolis, and W. C. Clarke. 1995. Physiological ecology of Pacific salmon. University of British Columbia Press. Vancouver, B.C.
Kessel, D. G. 2000. "Global warming- facts, assessment, countermeasures." Journal of Petroleum Science and Engineering. Volume 26. Pages 157 to 168.
Mazza, P. 1999. In hot water--A snapshot of the Northwest’s changing climate. Climate Solutions Special Report. Download.
Mote, P. W. and others. 2003. "Preparing for climate change: the water, salmon and forests of the Pacific Northwest." Climatic Change. Volume 61, Numbers 1 and 2. Pages 45 to 88.
Naiman, R. J., H. Decamps, and M. E. McClain. 2005. Riparia - Ecology, Conservation and Management of Streamside Communities. Elsevier Academic Press. Burlington, MA.
National Oceanic and Atmospheric Association. 2005. Annual Review, U.S. Drought, National Climate Data Center.
National Park Service. 1996. Elwha River Ecosystem Restoration, Draft Environmental Impact Statement. National Park Service, Olympic National Park, 600 East Park Avenue, Port Angeles, Washington, 98362.
Olympic National Park. 2007. Olympic National Park weather page.
Parmesan, C., and G. Yohe. 2003. "A globally coherent fingerprint of climate change impacts across natural systems." Nature. Volume 421. Pages 37 to 42.
Rapp, V. 2004. "Western forests, fire risk, and climate change." Pacific Northwest Research Station, Science Update Issue 6, USDA Forest Service. Download.
Schneider, S. H., and T. L. Root. 1998. Climate Change. U.S. Department of the Interior, U.S. Geological Survey.
Williams, J. W., S. T. Jackson, and J. E. Kutzbach. 2007. "Projected distribution of novel and disappearing climates by 2100 AD." Proceedings of the National Academy of Sciences. Volume 104, Number 14. Pages 5738 to 5742.
World Climate. 2007. Climate of the Elwha River in Clallam County.
Additional information
Binder, L. C. 2006. "Climate change and watershed planning in Washington State." Journal of the American Water Resources Association. Volume 42, Number 4. Pages 915 to 926.
Mantua, N. J., and S. R. Hare. 2002. "The Pacific Decadal Oscillation." Journal of Oceanography. Volume 58. Pages 35 to 44.
Mote, P. W. 2003. "Twentieth-century fluctuations and trends in temperature, precipitation, and mountain snowpack in the Georgia Basin-Puget Sound region." Canadian Water Resources Journal. Volume 28, Number 4. Pages 567 to 585.
Nolin, A. W., and C. Daly. 2006. "Mapping “at risk” snow in the Pacific Northwest." Journal of Hydrometeorology. Volume 7, Number 5. Pages 1164 to 1171.
Salthe, E. P. 2006. "Influences of a shift in North Pacific storm tracks on western North American precipitation under global warming." Geophysical Research Letters. Volume 33, Number 19. Article No. L19820.
Snyder, M. A. and L. C. Sloan. 2005. "Transient future climate over the western United States using a regional climate model." Earth Interactions. Volume 9. Pages 1 to 21.
Western Regional Climate Center. 2007. Historical Climate Information.