Recalculate ICESat-2 ATL11 height changes up to 20210715 #329
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Calculate Antarctic ice surface height range (hrange) and rate of ice surface elevation change over time (dhdt) up to 20210715! Supersedes 1db62e9. Involves n=302 million data points!! Reduced CPU cores from 16 to 4 to help with server memory limitations. Tweaked some xarray code to remove deprecation warnings. Also updated teaser dhdt image accordingly on the main README.md.
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New `dhdt_maxslp` function to calculate the maximum rate of elevation change over time (dhdt) for any consecutive paired value within an ATL11 time-series. This allows us to capture the signal of sudden elevation changes, even over a long period of time (>2 years) when active subglacial lakes that filled up may have drained and reverted to the old elevation, resulting in little of a dhdt trend (a problem with the `nan_linregress` method used in dedd0f4). This `dhdt_maxslp` function removes NaN values, does a rolling diff calculation, divides elevation over time to get dhdt values (for each consecutive pair), finds the index of the max absolute dhdt, and returns the maxslp result. Not too complicated, but it does take a bit of explaining so there's some ASCII art to help, and I'll make sure to produce a proper figure later.
Re-running the clustering algorithm to detect Antarctic subglacial lakes with ICESat-2 ATL11 data up to 20210715. There are now 221 potential active lakes compared to 193 before. Keeping the same DBSCAN hyperparameters as in the last run at ca79a32, specifically an eps of 3000 and min_samples of 300. On the Siple Coast, Lake WIX seems to have switched from filling to draining, and there have been a few more active subglacial lakes 'disappeared' such as Whillans 6, Lake 78, Kamb 5 and Kamb 7, Macayeal 4, etc. Really need to get the new dhdt_maxslp data from 16061b4 to work, but it's a lot noisier than I thought and I haven't managed to work out the best DBSCAN parameters to use. So just using the classic dhdt_slope data and battle-tested DBSCAN parameters for now.
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Reduces the active subglacial lake inventory count from 221 to 204. This gets rid of some most likely false positive lakes, in particular, a large one over the grounding zone of Pine Island Glacier.
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Refresh Antarctic active subglacial lake maps using new data up to 20210715. Specifically, we are using subglacial lake outlines from commit weiji14/deepicedrain@9073678 in weiji14/deepicedrain#329. Main code change is to update to PyGMT v0.5.0 syntax, such as directly plotting geopandas.GeoDataFrame objects! Text label placements remain the same, and I've thrown in the .geojson to .gmt conversion script (requires deepicedrain kernel) at the end of the notebook. Also updated thumbnails on main README.md.
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Since Subglacial Lake Whillans 6 'disappeared' in e5e91cd, shouldn't use it in the integration test. Oh yes, time to get back into this ICESat-2 project! Running things on a new workstation now and there's some exciting new libraries so best to wrap this up! Fixed a `TypeError: __init__() got an unexpected keyword argument 'calc_core_sample_indices'` because of scikit-learn/cuml API differences. Also gitignoring the dask-worker-space folder and some of the vector data files. Had to bump llvmlite from 0.36.0 to 0.38.0 in the poetry.lock file to be in line with conda installed version and prevent "ERROR: Cannot uninstall 'llvmlite'. It is a distutils installed project and thus we cannot accurately determine which files belong to it which would lead to only a partial uninstall". Similar business with d89186e.
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Reprocess delta_height (dh), height range (hrange) and rate of elevation change over time (dhdt) for the the whole of Antarctica over the 2019-03-29 to 2021-07-15 time period! Also calculate the maximum dhdt for the elevation time-series (dhdt_maxslp) ✨. Supersedes #304, continuation of #327.
TODO: