Sub-seasonal Arctic Lake Area Variability
Arctic and Boreal regions are home to the highest density/number of lakes on Earth. Understanding how these lakes are changing, on both seasonal and interannual time scales, is critical for assessing environmental sensitivity to climate change, monitoring the hydrology of these remote and often poorly studied regions, and constraining terrestrial freshwater methane emissions. While many studies have examined long-term, interannual changes in lake area, until recently, little research had focused on shorter-term changes in lake area due to a traditional tradeoff between high spatial and high temporal resolution satellite imagery.
Over the past 5 years, there has been rapid development of new, tiny satellites known as CubeSats by companies such as Planet Labs which now provide imagery of the entire land surface of the Earth at 3 meter resolution, every single day. This imagery has opened new possibilities for mapping short-term changes in lake area, but due to the newness of the CubeSat technology, it first required testing and development of novel methodology. The first project of my PhD involved testing a water classification and lake area change tracking method using Planet CubeSat imagery over a small area of the Yukon Flats during summer 2016. In this paper, published in Remote Sensing, we demonstrated that CubeSat imagery could be used to accurately map water area and thus could provide valuable insight into seasonal wetland and lake dynamics.
Following on this project, I then upscaled this method to be applicable over a much larger area by incorporating machine learning. As part of NASA’s Arctic-Boreal Vulnerability Experiment, I tracked changes in lake area over summer 2017 in four study areas in Northern Canada and Alaska, corresponding to the locations of our summer 2017 fieldwork. We identified a surprisingly hydrologically dynamic landscape, particularly in the poorly studied Canadian Shield where we found substantial sub-seasonal lake area variability. These results, published in Geophysical Research Letters, have implications for the estimation of freshwater methane and carbon dioxide emission, which is often higher along seasonally fluctuating lake margins. The press release for this paper can be found here.
Cooley, S.W., L.C. Smith, J.C. Ryan, L.H. Pitcher and T.M. Pavelsky (2019), Arctic-Boreal lake dynamics revealed using CubeSat imagery, Geophysical Research Letters. doi.org/10.1029/2018GL081584
Pitcher, L., T. Pavelsky, L. Smith, D. Moller, E. Altenau, G. Allen, C. Lion, D. Butman, S. Cooley, J. Fayne, and M. Bertram (2018), AirSWOT InSAR mapping of surface water elevations and hydraulic gradients across the Yukon Flats Basin, Alaska, Water Resources Research. doi.org/10.1029/2018WR023274
Cooley, S.W., L.C. Smith, L. Stepan and J. Mascaro (2017), Tracking dynamic northern surface water changes with high frequency Planet CubeSat imagery, Remote Sensing 9, 1309. doi.org/10.3390/rs9121306