Advances in lake ice monitoring methods based on remote sensing technology

Lake ice is not only an important part of the cryosphere but also one of the most direct indicators of global climate change. In the context of climate warming and intensified human activities, global lake ice presents a trend of delayed freeze onset date, advanced break onset date, shortened ice cover duration, and thinning ice thickness. This trend tends to last for a long time. Consequently, a series of chain reactions of lake physical hydrology, hydrochemistry, and ecosystem will inevitably be triggered, further heaving the burden of natural environment and habitat construction. Therefore, it is necessary to perform fine-scale monitoring and scientific analysis of spatiotemporal patterns on lake ice variations for further predicting the early warning of global climate change. Toward overcoming the limitation of in-situ surveys, remote sensing technique comes to play a significant role in lake ice monitoring, which can provide large-scale, long time series, and high temporal resolution data for lake ice research. Previous efforts always focus on lake ice and its response to climate change using different remote sensing sensors, parameters, and characteristics. Through reviewing pioneering research, this study presents a general review on the remote sensing data source and methods for lake ice studies as well as spatial and temporal variations of lake ice in global hotspots. This paper first reviews the development of the commonly used remote sensing data sources for lake ice monitoring, which include spaceborne and airborne remote sensing platforms and existing lake ice data products. Then, the methods of lake ice identification and retrieval of lake ice phenology and ice thickness parameters are compared and discussed. Threshold and index-based methods are commonly used in lake ice research. According to the previous studies, this review likewise summaries the research hotspots of lake ice and analyzes the spatial and temporal characteristics of lake ice variations. The research hotspots are mostly distributed in the Northern hemisphere, especially in Northern Europe, North America, and the Tibetan Plateau. In addition, influencing factors of lake ice variations, including climate factors and lake shape attributes, are discussed in this study. Finally, future development directions of lake ice study by remote sensing are discussed as follows: (1) to fully integrate multiple satellite data at medium and high spatial resolution to improve the accuracy of lake ice observations, particularly for small- and medium-sized lakes; (2) to reconstruct the long time series of lake ice phenology and thickness information and predict their future changes based on techniques such as big earth data and machine learning methods; and (3) to focus more on the research of past, present, and future of lake ice variation characteristics in the Tibetan Plateau, which is rather sensitive to climate change and remains largely unexplained. Remote sensing is an effective tool to monitor the variations of lake ice, yet what we should do imperatively is to advance the scientific understanding on climate change impacts and take immediate actions. © 2024 Science Press. All rights reserved.