Dynamic Lake Ice Movement on Lake Khovsgol, Mongolia, Revealed by Time Series Displacements from Pixel Offset with Sentinel-2 Optical Images

Jue Zhang,Ping He,Zhumei Liu,Xiaoping Hu

doi:10.3390/rs13244979

Abstract

As one of the most sensitive indicators of global climate change, seasonal ice-covered lakes are attracting gaining attention worldwide. As a large seasonal ice-covered lake located in Northern Mongolia, Lake Khovsgol not only provides important freshwater resources for the local population but also serves as a means of water transportation in summer and an important land-based activity for residents in winter. In this study, we used the sub-pixel offset technique with multi-temporal Sentinel-2 optical images to estimate the time-series displacement of lake ice in Lake Khovsgol from 7 December 2020 to 17 June 2021. With the processing of 112 Sentinel-2 images, we obtained 27 pairs of displacement results at intervals of 5, 10, and 15 days. These lake ice movement results covered three stages from ice-on to ice-off. The first stage was the lake ice growth period, which lasted 26 days from 7 December 2020 to 3 January 2021. Ice formation started from the south and extended northward, with a displacement of up to 10 m in 5 days. The second stage was the active phase of the ice cover, which took place from 3 January 2021 to 18 April 2021. Maximum displacement values reached 12 m in the east and 11 m in the north among all observations. The value of the lake ice movement in the north–south direction (NS) was found to be larger than in the east–west direction (EW). The third stage was the melting period, which closed on 17 June 2021. In comparison to the freezing date of November in past years, our results demonstrate the ice-on date of Lake Khovsgol has been delayed to December, suggesting a possible reason that the seasonal ice-covered lake located at the middle latitude has been affected by global warming. In addition, the lake ice movement of our results can reveal the regional climate characteristic. This study is one of the few cases to reveal the distribution characteristics and changing trends of lake ice on the Mongolia Plateau, providing a rare reference for lake ice research in this region.

Highlights

Seasonal ice-covered lakes, as one of the most sensitive indicators of response to greenhouse gas emissions, are closely related to regional ecological environment, production, and development in polar and high latitude regions, which have attracted increasing worldwide attention [1,2,3,4,5]
Our results showed that the monitoring of spatial and temporal variations of ice sheet displacements can be accomplished with uninterrupted high-density data gain (112 Sentinel-2 optical images), continuous acquisition times, and high-resolution matching (10 m) when constructing horizontal displacement measurements of seasonal ice sheet movements from
Sentinel 2 was found to perform well in the near-infrared band (B8), which could achieve an accuracy of approximately 1/10 pixel for the horizontal displacement of lake ice movement

Summary

Introduction

Seasonal ice-covered lakes, as one of the most sensitive indicators of response to greenhouse gas emissions, are closely related to regional ecological environment, production, and development in polar and high latitude regions, which have attracted increasing worldwide attention [1,2,3,4,5]. Lakes are important sources of atmospheric carbon dioxide and methane to the extent that they are thought to offset a majority share of the terrestrial carbon sink [6,7]. Km200 west theof the located in the northwest of Mongolia, about kmof west southern end of Lake Baikal near Russian Siberia (Figure 1). It is surrounded by three ridges southern end of Lake Baikal near Russian Siberia (Figure 1) It is surrounded by three and originated graben associated with surface faulting been developed by deridgesfrom andaoriginated from a graben associated with which surfacehas faulting which has been veloped by either collision from the Indian Plate’s northeastward movement or either remote collision from remote the Indian.

Results

Discussion

Conclusion