Arctic InSitu versus GRACE (ArcticInSituvGRACE) 2023

updated Arctic land ice mass balance output after:

Box, J. E., Colgan, W. T., Wouters, B., Burgess, D. O., O’Neel, S., Thomson, L. I., & Mernild, S. H. (2018). Global sea-level contribution from Arctic land ice: 1971–2017. Environmental Research Letters: ERL [Web Site], 13(12), 125012. https://doi.org/10.1088/1748-9326/aaf2ed 

The base data is from the WGMS compilation https://wgms.ch/data_databaseversions/ adding 'latest values' from https://wgms.ch/latest-glacier-mass-balance-data/

GLAMBIE info

Lead Author - First Name, Surname Jason,Box Lead Author - Email Address jeb@geus.dk Co-author - Name(s). Please separate multiple names with "," William T Colgan, Bert Wouters, David O Burgess, Shad O'Neel, Laura I Thomson Co-author - Email Address(es). Please separate multiple addresses with "," wic@geus.dk,b.wouters@uu.nl,david.burgess@nrcan-rncan.gc.ca,shad.oneel@gmail.com,l.thomson@queensu.ca

Group Name ArcticInSituvGRACE Danish Energy Agency and AMAP

Sponsoring Agency (project sponsor)

Methods

From Box et al. 2018: "Semi-empirical regional total mass balance assessment Akin to Dowdeswell et al (1997) and Meier et al (2007), we aggregate in situ glacier mass balance time series to upscale to regional values. We enhance the approach by an absolute calibration to GRACE estimates and by representing a later time period (the 2000s onward) with more pronounced climate change impacts on glacier mass balance. For each in situ mass balance record (i) having at least 80% of available data 1971–2017 (47 years), we calculate the 2003–2015 average (DBa) and standard deviation (s) and 1971–2017 anomalies (DBa’) relative to the W08 (years 2003–2015) baseline. Each record is divided by the standard deviation, i.e. stan- dardized as: DBa-prime i,y = (DBa i,y - DBa i,2003-2015) /sBa i,2003-2015 The individual glacier DBa¢i values are averaged over six regions (all but Greenland is) (table 1) and multiplied by the W08 regional GRACE mass balance averages (table 1). By this approach, we estimate mass balance totals for each region and year in the 1971–2017 interval in a way that is scaled to the GRACE mass balance retrievals. Lacking in situ mass balance record from Arctic Canada South, table 1 Arctic Canada North and South mass balance values were summed into a single regional value and thus the combined region wass represented by four Arctic in situ mass balance records." In this new (2023) version, Arctic Canada is split south/north. See regional notes below.

The in-situ data are available for a longer period than GRACE, so the regional mass balance can be estimated for the period before GRACE using the regression parameters.

Update of GRACE data processing in J Box files : /GRACE/Wouters/GRACE_Arctic_Wouters/GRACE_Arctic.py

Arctic Canada, North and South are separated based on the average GRACE mass balance ratio (r) between 2002 and 2015, r = 0.6557, i.e. South = all Arctic Canada r, and North = all Arctic Canada 1-r

Regional Notes

Arctic Canada

In Bert's GLAMBIE version of data, I am finding that ACN loses ice faster than ACS by 'only' a factor of 1.065x, or by 1.049x using the 2022 data I last received from Bert on Jan 2 2022. Incidentally, Box18 tabulated a ratio of 1.138 for "2003–2015", meaning Sept 2002 to Sept 2015 from a yet earlier version of Bert's data.

What I submitted to GLAMBIE a few months ago was in error. That scaling had ACS > ACN and by a factor of 1.52! My error was in estimating 2002-2015 mass balance average from annual hydrologic years that unlike a multi-month fit line (below) are quite sensitive to successive September to September hydrological year determinations. Further, in my too clever hydrological year determinations, I had employed gap-filling. Much more robust is obtaining the trend from the linear fit.

So, now I assign a regional scaling according to the latest Bert GRACE data; ACN loses ice faster than ACS by 'only' a factor of 1.065x. I already applied that after this code

Russian High Arctic (RHI)

Russian High Arctic (RHI) is here estimated based on regression with Svalbard (Svalbard vs RHI slope 1.1236, that is RHI mass balance is estimated to be 12% more negative than that of Svalbard) after RHI −22 GT/y from the 2000 to 2017 period (Sommer et al 2022): Sommer, C., Seehaus, T., Glazovsky, A., and Braun, M. H.: Brief communication: Increased glacier mass loss in the Russian High Arctic (2010–2017), The Cryosphere, 16, 35–42, https://doi.org/10.5194/tc-16-35-2022, 2022.

Iceland

Iceland can be extended before 1988. See issues.

GRACE data notes

The approach could be updated by making regressions vs regional z-scores and a longer GRACE time series

Greenland

Greenland mass balance is from:

Mankoff, Ken; Fettweis, Xavier; Solgaard, Anne; Langen, Peter; Stendel, Martin; Noël, Brice; van den Broeke, Michiel R.; Karlsson, Nanna; Box, Jason E.; Kjeldsen, Kristian, 2021, "Greenland ice sheet mass balance from 1840 through next week", https://doi.org/10.22008/FK2/OHI23Z, GEUS Dataverse, V449

Mankoff, K. D., Fettweis, X., Langen, P. L., Stendel, M., Kjeldsen, K. K., Karlsson, N. B., Noël, B., van den Broeke, M. R., Solgaard, A., Colgan, W., Box, J. E., Simonsen, S. B., King, M. D., Ahlstrøm, A. P., Andersen, S. B., and Fausto, R. S.: Greenland ice sheet mass balance from 1840 through next week, Earth Syst. Sci. Data, 13, 5001–5025, https://doi.org/10.5194/essd-13-5001-2021, 2021. doi: 10.5194/essd-13-5001-2021