Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8337
Title: Watershed geomorphology and snowmelt control stream thermal sensitivity to air temperature
Author: Peter J. Lisi, D. E. Schindler, T. J. Cline, M. D. Scheuerell, Patrick B. Walsh
Publication Year: 2015
Journal: Geophysical Research Letters
Volume: 42
Issue: 9
Pages: 3380-3388
Keywords: Climate change, thermal regime, MARSS, hydrology, Bristol Bay, Alaska.,

 How local geomorphic and hydrologic filters control the sensitivity of stream thermal regimes to variation in climatic conditions remains a critical uncertainty in understanding aquatic ecosystem responses to climate change. We used stable isotopes of hydrogen and oxygen in stream water to estimate contributions of snow and rainfall to 80 boreal streams in southwest Alaska, and show that differences in snow contribution are controlled by watershed topography. Multivariate time-series analysis of stream thermal regimes revealed that streams in rain-dominated, low-elevation watersheds were 5-8 times more sensitive to variation in summer air temperature compared to neighboring streams draining steeper topography whose flows were dominated by melted snow. Thus, the impact of climate warming on freshwater thermal regimes will be spatially heterogeneous across river basins as controlled by local watershed features. However, this thermal heterogeneity may be lost with reduced snowpack and increased ratios of rain to snow in stream discharge.

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Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Characterize relationships between habitat and ecosystem processes, climate variation, and the viability of organisms.