Spatially heterogeneous effect of the climate warming on the Arctic land ice
Abstract. Global warming has already substantially altered the Arctic cryosphere. Due to the Arctic warming amplification, the temperature is increasing more strongly leading to pervasive changes in this area. Recent years were notably marked by melt records over the Greenland Ice Sheet while other regions such as Svalbard seem to remain less influenced. This raises the question of the current state of the Greenland Ice Sheet and the various ice caps in the Arctic for which few studies are available. We here run the Regional Climate Model (RCM) Modèle Atmosphérique Régional (MAR) at a resolution of 6 km over 4 different domains covering all the Arctic grounded cryosphere to produce a unified Surface Mass Balance product from 1950 to present day. We also compare our results to large-scale indices to better understand the heterogeneity of the evolutions across the Arctic and their links to recent climate change. We find a sharp decrease of SMB over the western Arctic (Canada and Greenland), in relationship with the atmospheric blocking situations that have become more frequent in summer, resulting in a 41 % increase of the melt rate since 1950. This increase is not seen over the Russian Arctic and Svalbard permanent ice areas, where melt rates have increased by only 9 % on average, illustrating a heterogeneity in the Arctic SMB response to global warming.
Damien Maure et al.
Status: final response (author comments only)
- RC1: 'Comment on tc-2023-7', Shawn Marshall, 26 Apr 2023
- RC2: 'Comment on tc-2023-7', Anonymous Referee #2, 01 May 2023
Damien Maure et al.
Damien Maure et al.
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This is an interesting study, well-explained and with excellent Figures in support of the analysis and conclusions. I am not aware of a comparable study that considers the circum-Arctic mass balance with 'standardized' models. The emerging east-west patterns are interesting, systematic, and nicely explained, i.e., the conclusions are well supported by the model results and discussion. I support publication subject to clarification of a number of relatively minor considerations.
On a high level, it would be interesting to comment on the overall Arctic glacier (and Greenland) mass loss, focusing on the SMB (atmospheric climate signal) and the authors' sense of whether one can separate (i) the overall Arctic warming impact from (ii) the influence of atmospheric circulation anomalies. That is maybe like considering PC1 and PC2 in some kind of SMB pattern analysis, so perhaps that is another study. But I would welcome a short discussion from the authors on whether these are separable, how each contribution may be changing in time, and what that means for future decades - should we expect some persistence in this kind of atmospheric pattern (i.e., ridging over the western Arctic and Greenland)? Just discussion points.
l.18, "could modify the SMB" - I guess this is very clearly happening, beyond just conditional. Many prior studies show how changing T and P are modifying the SMB across Arctic ice caps, e.g. Huggonet et al. (2021), IPCC (2021) and references therein
l.23, "quick" is hard to define - seconds, minutes, months, years. Suggest being specific here, e.g., if you are referring to synoptic, seasonal, or interannual variability
l.28, see also Rajewicz and Marshall (2014) on this point. Not that this needs to be cited, but it directly assesses the anticyclonic circulation/ridging anomalies that are being discussed here, and notes how these strongly and simultaneously impact Arctic Canada and southern/western Greenland, of relevance to this manuscript. I would also note that this can be expected to be highly correlated with cool anonalies in the eastern subArctic, as ridging over the western Arctic and Greenland would typically be accompanied by a trough (cooler conditions) in the eastern North Atlantic and Eurasian sector of the Arctic
l.34, suggest rewording, "a unified estimate is still lacking"
l.39, "aims", plural
l.53, the 6 km resolution is high in some ways, for the size of the domain, but does not resolve many of the smaller ice masses, particularly in mountainous regions such as coastal Greenland and Baffin Island. On this particular point on l.53, omitting grid cells that are less than 50% ice covered, I worry if this might exclude a large amount of the ablation area of many of the glaciers and ice caps. This could cause a systematic underestimation of ablation, by excluding a lot of marginal ice area. It will be good to discuss this and even compare the captured ice area/hypsometry to what one would see at 1 km, for example.
l.66, “over the ocean”
l.67, suggested rewording to "surface pressure, sea ice concentration, and sea surface temperature"
Figure 2, "annual time scale" - are these averaged for the decade? Please clarify in the caption
l.137-138, discussion of the lower interannual variability of the altimetry data. This would be helpful and interesting to compare with WGMS SMB data which is available for some of these regions (e.g., Artctic Canada, Iceland) - what does the interannual variability look like there? It would be very instructive to include a third box-whisker for the WGMS data where it is available, recognizing that it is not covering the full domain in any of these regions. Particularly around whether the modelled interannual variabiliy is realistic, and to compare SMB with SMB directly for all regions where this is possible.
l.151-152, "while this decrease is mainly driven by Greenland..." True, but this is mostly because Greenland dominates the total mass loss? vs. the % change being the driver, as argued here.
Figure 4, Please define RU and SF in the caption
l.156, "over Baffin Island" (no the, here and throughout)
l.157, Are these numbers right, for Baffin Island? Something is sending up red flags for me here. The glacierized area of Baffin Island is much less than Ellesmere, so the modelled runoff and mass loss from here seems out of proportion compared with Devon and Ellesmere. There are a lot of smaller ice masses that may not be well-captured at 6 km. This might make sense in the context of more negative specific mass balance rates here (average m/yr of thinning), but it would be helpful to discuss and present this for the different regions, based on the RGI glacier areas.
l.216, I don't think "desertic" is a word. Recommend just "dry" ?
l.248, "that those regions" - Do you mean the eastern Arctic? Be specific here.
l.264, I think that here and throughout, this should be Novaya Zemlya. Nova Zembla is an island in the Canadian Arctic, near Baffin Island, but is not what the authors are referring to, I think
l.268, Fig. 9a
l.269, "has been -62 Gt/yr"