Spatial-temporal variations of maximum surface water temperature in Arctic Fennoscandian lakes

The remote Arctic region is covered with numerous small lakes affected my current climate warming. There are little data on their thermal features, however, which hinders our understanding of the possible ecosystem impacts of warming climate and climate feedbacks at large spatial scales. We investigated spatial - temporal variations of summer lake surface temperatures (LSTs’) in 12 Arctic lakes and explored the predominant drivers by continuous year round observations of surface water temperatures. Our results suggest the general annual cycle pattern of summer water temperature: 1) the warming - up season lasted from May to July (or August) until the water temperature reached its maximum, and then the water temperature decreased until freezing in fall; and 2) the large regional heterogeneity existed in changes of summer LSTs. Futhermore, our results illustrate that July air temperature, maximum lake depth and longitude explained most of the variance in summer LSTs (>75%), and the remaining variance was related to geographic location (e.g. altitude and latitude), lake morphometric features, such as lake area and catchment area, and geochemical characteristics, i.e. turbidity and dissolved organic carbon (DOC) content. Our results provide new insights into thermal responses of small Arctic lakes with different environmental settings to climate change.