| Summary: | Understanding the impacts of climate change on freshwater ecosystems is highly dependent on quantifying the associated changes in instream temperatures. However, this can be complicated because these temperatures are related to both changing meteorology (e.g., air temperature and precipitation) and hydrology (e.g., instream flows and lateral inflows). The ability to predict climate related changes on instream thermal regimes in Arctic streams is limited by the minimal understanding of key processes and the availability of data to quantify heat fluxes. We hypothesized that the dominant heat fluxes within Arctic streams are similar to those in temperate climates but that the relative magnitude of the heat fluxes differ, and that quantification of lateral inflows is key in predicting water temperatures. We first found that temperate-zone and Arctic river temperatures are controlled by similar processes, with a few key differences. The differences, however, depended on location within the watershed and hydrologic condition. In general, solar radiation and other radiative exchanges controlled river temperatures at the most downstream and upstream locations in the watershed. However, there were other key heat fluxes in the upper locations that varied with instream flows. During large rain events and high river flows, the relatively steep terrain in the upper portion of the watershed delivers water efficiently and surface and groundwater inflows from the watershed become an important control on river temperatures (See King et al., 2016 Water Resources Research, doi:10.1002/2015WR017965 for more information). During dry periods when the river flow is low, we found that the exchange of water from the channel to the cold river bottom sediments and back became important and kept the river temperatures cool enough for fish (See King et al., 2019 Water Resources Research, for more information). In temperate-zone rivers these low flow conditions tend to create conditions that are too warm for the native fish, but in arctic rivers with frozen sediments below, this channel-sediment exchange keeps the river cool even during warm, dry conditions. Other related findings and publications include: King et al. 2018 (doi:10.1002/2017WR021868), Neilson et al. 2018 (https://doi.org/10.1029/2018GL078140), Cory et al. 2015 (doi:10.5194/bg-12-6669-2015). The data archived here includes water temperature, volumetric flow rates or discharge, weather time series, and other data sets collected to answer investigate these research questions.Further data and metadata can be found on the hydroshare repository. https://www.hydroshare.org/resource/713e8be6255d404980a3f67cef7337ee/
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