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mankoff / sankey

Sankey diagram for ice sheet mass flow
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Grounding line retreat #10

Open mankoff opened 1 month ago

mankoff commented 1 month ago

https://github.com/mankoff/sankey/blob/8476eb79dadb205b149e425743b99050876f10a1/dat/aq_baseline.csv#L10

Need estimate of GZ retreat in Antarctica

chadagreene commented 4 weeks ago

I think accurate numbers of grounded-ice mass change resulting from GL retreat are gonna be hard. I don't know of any continuous, time-evolving GL product. Stitching together segments of landward limits of flexure seems pretty labor intensive, and there are lots of areas of missing InSAR data or different interpretations of landward limits of flexure depending on things like what part of the tidal cycle was sampled, etc.

The easiest approach I can think of is to use a hydrostatic assumption and calculate changes in the floating ice volume resulting from dh/dt. (Konrad et al. 2018 took a similar approach) Doing this would be relatively straightforward, but getting DEMs to line up with dh/dt might involve a bit of missing data around the edges of the ice sheet. And many of the dh/dt products apply an a-priori assumption about where the grounding line is for processing, so I'm not sure what that means for trying to apply gridded dh/dt for estimates of GL migration.

Is there any other approach you're thinking of?

mankoff commented 3 weeks ago

I didn't have a 'grounding line retreat' issue for Greenland because I was neglecting it, but since you raise the issue we should address it.

The easiest way might be to get a few sentences from Millan, or text from https://doi.org/10.1038/s41467-023-42198-2 . For example, they report

Retreat of the Petermann’s GL was reported to be 7 km between 1992 and 2021,

So if we have an estimate of thickness and width near the GZ, we can get a rough estimate of average annual mass flow due to retreat. Uncertainty may be large, and overall this is a small term in Greenland.