Abstract
Lake ice is an important component in understanding the local climate as changes in temperature have an impact on the timing of key ice phenology events. In recent years, there has been a decline in the in-situ monitoring of lake ice events in Canada and microwave remote sensing imagery from synthetic aperture radar (SAR) is more widely used due to the high spatial resolution and response of backscatter to the freezing and melting of the ice surface. RADARSAT-2 imagery was used to develop a threshold-based method for determining lake ice events for mid-latitude lakes in Central Ontario from 2008 to 2017. Estimated lake ice phenology events are validated with ground-based observations and are compared against the Moderate Resolution Imaging Spectroradiometer (MODIS band 2). The threshold-based method was found to accurately identify 12 out of 17 freeze events and 13 out of 17 melt events from 2015–2017 when compared to ground-based observations. Mean absolute errors for freeze events ranged from 2.5 to 10.0 days when compared to MODIS imagery while the mean absolute error for water clear of ice (WCI) ranged from 1.5 to 7.1 days. The method is important for the study of mid-latitude lake ice due to its unique success in detecting multiple freeze and melting events throughout the ice season.
Highlights
Changes detected in the Northern Hemisphere (i.e., Central North America, Northern Europe, and Russia) lake ice conditions since 1855 have shown a delay in ice on dates by 10.7 days and earlier ice off dates by 8.8 days [1]
We developed a RADARSAT-2 lake ice phenology threshold-based method that was successful at detecting multiple freezing and melting events for lakes in Central Ontario when compared to both
We developed a RADARSAT-2 lake ice phenology threshold-based method that was successful at detecting multiple freezing and melting events for lakes in Central Ontario when compared to both shoreline imagery and visible remote sensing images
Summary
Changes detected in the Northern Hemisphere (i.e., Central North America, Northern Europe, and Russia) lake ice conditions since 1855 have shown a delay in ice on dates by 10.7 days and earlier ice off dates by 8.8 days [1]. There are two main sources of lake ice data in Canada: a weekly product produced by the Canadian Ice Service (CIS) for ~136 lakes [7] across the country with ice charts for Great Lakes (https://www.canada.ca/en/environment-climate-change/ services/ice-forecasts-observations/latest-conditions.html) and the IceWatch program where data are collected by volunteers [8,9]. While beneficial, both programs have spatial and temporal limitations with respect to the number of lakes monitored and the frequency of observations. Remote sensing is more cost effective compared to traditional point collection as a single image can be used to monitor lakes over a large region and some satellites (i.e., MODIS, AVHRR, and RADARSAT-2 at northern latitudes) have a daily temporal resolution allowing the possibility for capturing a continuous record
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