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

Samuel E Tuttle,Alan Werner,Grant E Gunn,Michael J Retelle,Erin L Bunting,Steven R Roof

doi:10.3390/rs14061311

Samuel E Tuttle, Alan Werner + Show 4 more

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https://doi.org/10.3390/rs14061311

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Abstract

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 Linnévatnet, 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 Linnévatnet 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 Linnévatnet 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.

Highlights

Two key dates in the annual lake ice cycle were analyzed in this study: freeze-up end (FUE) and break-up end (BUE)
We identified a single date each year where the lake became completely ice-free in the spring (BUE) and a single date where the lake became completely ice-covered in the fall (FUE), remaining ice-covered for the rest of the winter
The process of spring melting of lake ice can take over a month. This is evident in both the Sentinel-1 time series, in which a date of first spring melting can often be identified, as well as the moderate-resolution imaging spectroradiometer (MODIS) surface reflectance time series, which shows a decrease in surface reflectance that lasts a month or more (Figure 4)

Summary

Introduction

Arctic regions are highly responsive to climate change, with large climate shifts occurring over the past two decades [1–3]. It is important to document changes in arctic climate because they can instigate further effects of global consequence [4]. Arctic lakes are sensitive climate indicators because they reflect ambient environmental conditions and effectively integrate short-term variations in atmospheric conditions [5,6]. Past studies have shown that lake ice phenology is primarily driven by local air temperature [7–9], and depends on a variety of secondary meteorologic, hydrologic, morphologic, and geographic factors [9–12]. The phenology of lake ice (i.e., timing of ice formation and break-up) influences a variety of lake properties, including water temperature distribution, stratification, Remote Sens.

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