PS 37-37 - Central Alaska Network (CAKN) Streams Monitoring Program: Analysis reveals long-term trends in stream temperatures in National Parks across central Alaska.

Abstract: Stream temperature plays a vital role in stream ecology, but little is known about how stream temperatures have changed across Alaska’s central parks. Recording of continuous stream temperature data at sites across the Central Alaska Network of the National Park Service began in 2008 as a part of the Stream Monitoring Program. Data records from 15 stream sites, located in two of the park units (Denali National Park and Preserve and Wrangell-St. Elias National Park and Preserve), were selected for non-parametric trend analysis because they were considered to be of sufficient length and quality to be analyzed for long-term trends. Statistically significant trends in annual temperatures were identified for 3 of the 15 streams, and trends in seasonal temperatures (May to October) for 3 other streams. This analysis also revealed significant trends in at least one month for all of the sites except one. Over half of the sites (8 of 15) showed an increase in at least one temperature parameter of over 0.1⁰C per year (1⁰C per decade) and almost half of the sites (7 of 15) showed an increase in temperatures in at least 3 months over the duration of the data record. The climatic factors responsible for these changes have yet to be determined, but it is likely that these changes are related to the long-term climate change trends occurring across the region. Analyses are currently being run on climatic factors that may be driving stream temperature change. These factors include air temperature, precipitation, solar radiation, snow depth, and soil temperature. Long-term changes in stream temperature may have cascading effects on stream ecology across Alaska and, therefore, it is necessary to understand the forces that drive stream temperature changes as an important link in the chain between climate change and stream ecosystems.