Arctic & Antarctic Icesheet Mass Balance As you can see from the previous posts until late 2022 I was posting data and graphs on t he progress of icesheet mass losses using data from the GRACE-FO satellites. These satellites replaced the GRACE satellites and was undertaken by a partnership between Germany and NASA/JPL. Data was being produced by both JPL and Germany (from the Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences, Dresden)
There have been no updates in recent months. I asked both NASA/JPL and the German Institute "pourquoi". Both replied that producing the data involved data from many sources applied to the GRACE-FO data and was continually evolving, isostatic rebound & oblateness (
see extract from paper on oblateness below)
I have now received a much more informative email from Herr Professor Frank Flechtner - see below. I was taken aback to read that a major reason for delay is "
we are all doing that work without dedicated funding".
Amazing - ice sheet mass loss and consequent sea level rise is an major threat to many who live on the coast and large low lying areas - e.g.s Bangladesh, Louisiana. Having spent a fortune on putting the satellites up there not having the relatively minor funding to support all the projects that use the data is just....... words fail me.
At least he says that I (& the ASIF) are exactly the sort of users they want to reach
Ho hum
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Frank Flechtner
24 Feb 2023, 10:42
Dear Matthew,
first of all the Greenland ice mass balance site is still available. I do not know when the direct link has changed, but if you simply google "GravIS and GFZ" you still arrive at
http://gravis.gfz-potsdam.de. There you could simply click on the corresponding ice sheet sub-pages for Greenland Ice Sheets (GIS) and Antartica Ice Sheets (AIS). The direct links are
http://gravis.gfz-potsdam.de/gis and
http://gravis.gfz-potsdam.de/ais.
The current status is indeed still August 2022. The reasons behind that are a) the delay of 60 days to produce Level-2 gravity fields in the GRACE-FO Science Data System and b) minimum 30 days to combine L2 products from different centers to a combined solution (done in Bern/Switzerland, see also reply from Thorben) and c) also some time to produce AIS/GIS. This means that the September 2022 data could be converted to Level-3 / 4 data theoretically not before early January and October 2022 not before early February this year. But as y
ou state, they are not there. The reason is that we are all doing that work without dedicated funding. At GFZ we have worked instead in the past 2-3 months to realize a new Groundwater Water Storage (GWS) sub-page which can be accessed at
http://gravis.gfz-potsdam.de/gws. I guess that this new feature was the reason for the new 3 character long sub-page names. These new products are a result of a EU funded project "Global Gravity-based Groundwater Product" which ended December 31 and which was presented at the final meeting this week. So a lot of preparations were needed. Details on G3P can be found in the sub-page.
So once again: we are very happy that you use our products and you are exactly a user we are looking for! And we will also try to provide the L3 products in time. But sometimes our capacities are simply limited and the regular 90-100 days delay gets longer. We will try to provide the missing products for 2022 soon but cannot give a concrete date today. Therefore I cc also some colleagues involved and advice you to simply visit GravIS frequently. You could also write a script and check the available GravIS data sets at the GFZ ISDC archive regularly. At the moment you see at
https://isdc.gfz-potsdam.de/grace-fo-isdc/grace-fo-gravity-data-and-documentation/ the AIS/GIS data "GRAVIS-3_2002095-2022243_COSTG_0100_GIS_*". This string could be analyzed to inform you automatically when a new product has arrived.
Thanks
Frank
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This paper concludes that annual icesheet mass loss is understated by about 15 GT per year in Antarctica and 3.5 GT in Greenland, implying an additional 0.08 mm sea level rise. Not much per year but over a long time span - a lot.
The paper was published in June 2019 but it looks like the results are only now being built into the analyses of GRACE-FO data.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL082929Improved Earth Oblateness Rate Reveals Increased Ice Sheet Losses and Mass-Driven Sea Level RiseAbstract
Satellite laser ranging (SLR) observations are routinely applied toward the estimation of dynamic oblateness, C20, which is the largest globally integrated component of Earth's time-variable gravity field. Since 2002, GRACE and GRACE Follow-On have revolutionized the recovery of higher spatial resolution features of global time-variable gravity, with SLR continuing to provide the most reliable estimates of C20. We quantify the effect of various SLR processing strategies on estimating C20 and demonstrate better signal recovery with the inclusion of GRACE-derived low-degree gravity information in the forward model. This improved SLR product modifies the Antarctic and Greenland Ice Sheet mass trends by −15.4 and −3.5 Gt/year, respectively, as compared to CSR TN11, and improves global mean sea level budget closure by modifying sea level rise by +0.08 mm/year. We recommend that this new C20 product be applied to RL06 GRACE data products for enhanced accuracy and scientific interpretation.
Key Points
- New satellite laser ranging C20 solution reveals larger Antarctic and Greenland ice mass losses and mass-driven sea level rise
- The new C20 result improves closure of the global mean sea level budget and agreement with an independent Antarctic ice mass assessment
- We recommend this new product for replacing the GRACE C20 values for science applications
