Arctic river temperature dynamics in a changing climate

Climate change in the Arctic is expected to have a major impact on stream ecosys-tems, affecting hydrological and thermal regimes. Although temperature is importantto a range of in-stream processes, previous Arctic stream temperature research is lim-ited—focused on glacierised headwaters in summer—with limited attention to snow-melt streams and winter. This is the first high-resolution study on streamtemperature in north-east Greenland (Zackenberg). Data were collected from fivestreams from September 2013 to September 2015 (24 months). During the winter,streams were largely frozen solid and water temperature variability low. Spring ice-off date occurred simultaneously across all streams, but 11 days earlier in 2014 com-pared with 2015 due to thicker snow insulation. During summer, water temperaturewas highly variable and exhibited a strong relationship with meteorological variables,particularly incoming shortwave radiation and air temperature. Mean summer watertemperature in these snowmelt streams was high compared with streams studied pre-viously in Svalbard, yet was lower in Swedish Lapland, as was expected given latitude.With global warning, Arctic stream thermal variability may be less in summer andincreased during the winter due to higher summer air temperature and elevated win-ter precipitation, and the spring and autumn ice-on and ice-off dates may extend theflowing water season—in turn affecting stream productivity and diversity.