Analyze active subglacial lake mega-clusters #210
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Re-running the clustering algorithm to detect Antarctic subglacial lakes with ICESat-2 ATL11 data up to 20200930. Keeping the same hyperparameters as in the last run at cb9a0d2. There are some new draining/filling lakes (e.g. Lake 12 on Whillans Ice Stream), and some which disappeared either because of the improved ATL11 algorithm's noise reduction (e.g. over the Transantarctic Mountains) or because the dhdt trend has flattened (e.g. MacAyeal 3?). Having a hard think of whether dhdt is a good 'signal' to use for active subglacial lake detection, or whether hrange would be better since noise levels are lower now, or if something fancier would need to be used. Also should play around with the hyperparameters a little bit, to do in the next couple of commits or in a separate Pull Request.
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Look at not one but multiple active subglacial lakes! Examples include: Lake 78, Subglacial Lake Conway, Subglacial Lake Mercer and Subglacial Lake Whillans on the Siple Coast; and Recovery 2 on Recovery Glacier. Also renumbered all the lake ids for the single lakes. The subglacial_lakes.feature file splits the single and mega-cluster lake tests. Note that the mega-cluster test won't run on CI until deepicedrain v0.4.0 is released. Really required a lot of refactoring to handle multiple lake polygons. Bounding box region is now determined using a convex hull so that it works for single or multiple polygons. Lakes are dissolved into a MultiPolygon (geopandas v0.8.0 requiring a dissolve field, problematic for Lake 78 that spans Whillans and Mercer basins). The lake outlines are saved to an OGR GMT format which is actually quite nice as it can be shared around.
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There are some active subglacial lakes which appear to be situated quite close to each other and form a sort of 'mega-cluster' (for lack of a better term). This is made possible with ICESat-2's superb geolocation accuracy. Below is an example for Subglacial Lake Whillans.
There are also other ones on the Siple Coast like Lake 78, Subglacial Lake Conway, Subglacial Lake Mercer; and also Recovery 2 on Recovery Glacier.
TODO:
Retune hyperparameters for active subglacial lake clustering algorithm(TODO in separate PR)References: