Monitoring changes in seasonal lake inundation regimes in the Mackenzie River Delta using Sentinel-1 SAR time series
Abstract
The Mackenzie River Delta (MRD) is one of the largest Arctic river deltas in the world and is uniquely characterized by tens of thousands of small lakes maintained by annual flooding of from the Mackenzie River. Variable inundation in these lakes drives a range of ecosystem processes, including carbon cycling and maintenance of aquatic habitats. With future climate scenarios in the MRD including the possibility of altered river flow regimes, how lakes respond to changes in river hydrology remains a key question in the MRD. In this study, we developed a workflow for the delineation of individual lakes and the monitoring of lake extent dynamics using a dense time series of Sentinel-1 SAR images acquired during an "average" (2019) and "wet" year (2021). First, we used a random forest model to classify open water and flooded vegetation in each image and defined lake features based on inundation persistence through time. We then computed the coefficient of variation of lake extent for each lake feature and each year. We observed significant spatial autocorrelation of lake variability in several regions across the delta, with the most notable clustering occurring near Beaufort Sea outlet. Seasonal variability was mostly driven by early-season flooding resulting from ice-jam floods in the spring. Results of a paired Wilcoxon sum-rank test showed that lake variability increased significantly in 2021 (p << 0.01; moderate effect size). Changes between 2019 and 2021 were most pronounced in lakes and wetlands smaller than 1 hectare, suggesting preferential susceptibility of these features to interannual changes in flow conditions. This study represents the first delta-wide, multi-year assessment of seasonal lake inundation regimes in the MRD. With changing river flow conditions having a significant but preferential impact on lake variability, ongoing research is investigating specific environmental drivers of the susceptibility of lakes to climate-induced changes in the MRD.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.C52B..07D