Evaluation of Satellite-Derived Estimates of Lake Ice Cover Timing on Linnevatnet, Kapp Linne, Svalbard Using In-Situ Data

Arctic lakes are sensitive to climate change, and the timing and duration of ice presence and absence (i.e., ice phenology) on the lake surface can be used as a climate indicator. In this study of Linnevatnet, one of the largest lakes on Svalbard, we compare inferences of lake ice duration from satellite data with continuously monitored lake water temperature and photographs from automatic cameras. Visible surface reflectance data from the moderate-resolution imaging spectroradiometer (MODIS) were used to observe the change in the lake-wide mean surface reflectance of Linnevatnet from 2003-2019, and smoothing splines were applied to the to determine the date of summer ice-off (also called break-up end-BUE). Similarly, BUE and fall ice-on (or freeze-up end-FUE) were determined from lake-wide mean time series of Sentinel-1 microwave backscatter from 2014-2019. Overall, the ice timing dates identified from the satellite observations agree well with the in-situ observations (RMSE values of approximately 2-7 days for BUE and FUE, depending on the method and in-situ dataset), lending confidence to the accuracy of remote sensing of lake ice phenology in remote Arctic regions. Our observations of Linnevatnet indicate that BUE dates do not have a significant trend, while FUE dates have been occurring approximately 1.5 days later per year during the study period. These results support an overall decrease in annual duration of lake ice cover in this part of Svalbard.

Automated summary

Arctic lakes' ice phenology, specifically the timing and duration of ice presence and absence, can serve as a climate indicator, and satellite observations are accurate in measuring this phenomenon. The study of Linnevatnet lake on Svalbard supports a decrease in the annual duration of lake ice cover in this area.