Mapping Arctic Lake Ice Backscatter Anomalies Using Sentinel-1 Time Series on Google Earth Engine

• Published in: Remote Sensing
• Main Authors: Georg Pointner, Annett Bartsch
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2021
• Subjects: arctic; lake ice; SAR; change detection; methane; Yamal; Science; Q; Arctic; Arctic Lake; The Sentinel; Yamal Peninsula; lena delta; Alaska; Siberia
• Online Access: https://doi.org/10.3390/rs13091626; https://doaj.org/article/ea6c84a397ef42e9b18b6e944ef00ff5

Seepage of geological methane through sediments of Arctic lakes might contribute conceivably to the atmospheric methane budget. However, the abundance and precise locations of such seeps are poorly quantified. For Lake Neyto, one of the largest lakes on the Yamal Peninsula in Northwestern Siberia, temporally expanding regions of anomalously low backscatter in C-band SAR imagery acquired in late winter and spring have been suggested to be related to seepage of methane from hydrocarbon reservoirs. However, this hypothesis has not been verified using in-situ observations so far. Similar anomalies have also been identified for other lakes on Yamal, but it is still uncertain whether or how many of them are related to methane seepage. This study aimed to document similar lake ice backscatter anomalies on a regional scale over four study regions (the Yamal Peninsula and Tazovskiy Peninsulas; the Lena Delta in Russia; the National Petroleum Reserve Alaska) during different years using a time series based approach on Google Earth Engine (GEE) that quantifies changes of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi>σ</mi><mn>0</mn></msup></semantics></math> from the Sentinel-1 C-band SAR sensor over time. An algorithm for assessing the coverage that takes the number of acquisitions and maximum time between acquisitions into account is presented, and differences between the main operating modes of Sentinel-1 are evaluated. Results show that better coverage can be achieved in extra wide swath (EW) mode, but interferometric wide swath (IW) mode data could be useful for smaller study areas and to substantiate EW results. A classification of anomalies on Lake Neyto from EW <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Δ</mi><msup><mi>σ</mi><mn>0</mn></msup></mrow></semantics></math> images derived from ...