the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Reconstructed glacier area and volume changes in the European Alps since the Little Ice Age
Abstract. Glaciers in the European Alps have experienced drastic area and volume loss since the end of the Little Ice Age (LIA) around the year 1850. How large these losses were is only poorly known as, published estimates of area loss are mostly based on simple up-scaling and alpine-wide reconstructions of LIA glacier surfaces are lacking. For this study, we compiled all digitally available LIA glacier extents for the Alps and added missing outlines for glaciers >0.1 km2 by manual digitising. This was based on geomorphologic interpretation of moraines and trimlines on very high-resolution images in combination with historic topographic maps and modern glacier outlines. Glacier area changes are determined for all glaciers with LIA extents at a regional scale. Glacier surface reconstruction with a Geographic Information System (GIS) was applied to calculate (a) glacier volume changes for the entire region from the LIA until today and (b) total LIA glacier volume in combination with a reconstructed glacier bed. The glacier area shrunk by 2405 km2 (-57 %) from 4211 km2 at the LIA maximum to 1806 km2 in 2015 and volume was reduced from about 281 km3 around 1850 to 100 km3 (‑65 %) in 2015, roughly in line with previous estimates. In the mean, glacier surfaces lowered by -43.3 m until 2015 (-0.25 m a-1), which is three-times less than observed over the 2000 to 2015 period (-0.82 m a-1). Strongest volume losses occurred around 1600 m and at least 1832 glaciers melted away completely. Many glaciers have now only remnants of their former coverage left, which led to deglaciation of entire catchments. The new datasets should support a wide range of studies related to the effects of climate change in the Alps.
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Status: open (until 04 Aug 2024)
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CC1: 'Comment on egusphere-2024-989', Melaine Le Roy, 06 May 2024
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Dear,
First, congrats to the authors for this long-awaited and well conducted work!
I have two comments on the manuscript:
1) Regarding Western Alps outlines
The Figure 2 shows Ecrins massif with 'new' outlines in 'blue'.
However, these LIA glacier outlines were already available (please see the figure attached here) in Marie Gardent’s 2014 PhD thesis (where the 'yellow' outlines you use originate I suppose)
So why have you redigitized them and presented them as new here (Fig. 2)?
By the way, the two Gardent’s references listed at the end are not actually quoted anywhere in the main text/figures of the manuscript.
So, why not quoting them in the caption of Figure 2, as it seems yellow outlines come from them?
If not, please provide a reference here for previously available outlines.
2) Regarding the timing of LIA maximum extent
It sounds to me somehow misleading and too simplistic to present differences in the timing of LIA maxima as depending only on the geographical location (e.g Western Alps/Italy in 1820 CE vs Austria in 1850 CE) as it was done here in the Introduction of the manuscript.
Better, the response time of glaciers should be mentioned as one of the (most likely) explanations for the differences in the chronology of LIA glacial maxima.
Indeed, we showed recently in two review papers dealing with the early LIA period (https://journals.sagepub.com/doi/full/10.1177/09596836221088247) and the Holocene (https://www.sciencedirect.com/science/article/abs/pii/B9780323997126000180?via%3Dihu) in the Alps, that (small) glaciers reached LIA maximum extent during any periods of LIA glacier maxima. For instance, many small glaciers, located from the Ecrins massif (to the west) up to the Tirol (to the east), reached absolute LIA maxima during the early 14th century.
The LIA chronology is therefore biased towards large (and most slowly reacting) glaciers because majority of available dates come from these sites, where most work has been carrying out in the past.
Related comment for Line 42:
‘in contrast to other regions in the world, extent differences (e.g. between 1850, 1820 or 1600) are small in the Alps’
Please provide references to support your point here. This affirmation does not seem straightforward to me at all.
Mainly because:
- Even if it’s relatively true at large Alpine glaciers, it is less at small glaciers.
- But foremost, dates with temporal resolution high enough to assert this (archives, tree rings) are barely available outside the Alps
Kind regards
Melaine Le Roy
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AC2: 'Reply on CC1', Johannes Reinthaler, 25 Jun 2024
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The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-989/egusphere-2024-989-AC2-supplement.pdf
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CC2: 'Comment on egusphere-2024-989', Riccardo Scotti, 10 Jun 2024
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Dear Editor, dear authors,
Considering the topic of the manuscript under discussion, I would like to flag to the authors prior studies that have focused on LIA glacier extent within the Italian region of Lombardy.
In lines 89-90 the authors state: “The largest regions without published LIA outlines were the Italian region of Lombardy and parts of the Dauphiné Alps (see 89 Table S3 for a list of regions with previously missing LIA glacier extents).”In this context, relatively recent LIA glacier extent reconstructions have been conducted and published for sectors of the Lombardy region. Scotti et al. (2014) dealt with the Livigno Alps, Monte Disgrazia Massif and the Orobie Range. Scotti et al. (2017) and Scotti and Brardinoni (2018) focused on Dosdè and Val Viola. Finally, Hagg et al. (2017) have conducted LIA glacier mapping in the Suretta Sud glacier in Valle Spluga.
The mapping approach in the foregoing studies entailed visual interpretation of sequential historical aerial photos and a recent LiDAR-derived hillshade raster, which was complemented by inspection of historical ground-based oblique pictures and historical maps, as well as by fieldwork.
To properly acknowledge prior work on the reconstruction of LIA glacier extent in Lombardy, I’d kindly ask the authors that the foregoing studies be cited in lines 89-90, and/or in lines 32-38 of the original manuscript.Best regards,
Riccardo Scotti
References:
HAGG, W., SCOTTI, R., VILLA, F., MAYER, E., HEILIG, A., MAYER, C., TAMM, W., HOCK, T. (2017): Evolution of two cirque glaciers in Lombardy and their relation to climatic factors (1962–2016). Geografiska Annaler: Series A, Physical Geography, 99(4), 371-386. https://doi.org/10.1080/04353676.2017.1368834SCOTTI, R., BRARDINONI, F., CROSTA, G.B. (2014): Post-LIA glacier changes along a latitudinal transect in the Central Italian Alps. The Cryosphere, 8, 2235–2252. https://doi:10.5194/tc-8-2235-2014
SCOTTI, R., BRARDINONI, F., CROSTA, G.B., COLA, G., MAIR, V. (2017): Time constraints for post-LGM landscape response to deglaciation in Val Viola, Central Italian Alps. Quaternary Science Reviews, 177, 10-33. https://doi.org/10.1016/j.quascirev.2017.10.011
SCOTTI, R., BRARDINONI, F. (2018): Evaluating millennial to contemporary time scales of glacier change in Val Viola, Central Italian Alps. Geografiska Annaler: Series A, Physical Geography ,100 (4), pp.319-339. https://doi.org/10.1080/04353676.2018.1491312
Citation: https://doi.org/10.5194/egusphere-2024-989-CC2 -
AC1: 'Reply on CC2', Johannes Reinthaler, 25 Jun 2024
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Thank you very much for pointing us to these studies which we can certainly include when discussing earlier work. Our statement in L89/90 referred to missing digital outlines (downloadable in shape file format from a given link) rather than publications about outlines. So thank you for providing us the LIA outlines for Val Viola via our separate request. Please send those for the other regions also to the GLIMS glacier database when they are ready.
Citation: https://doi.org/10.5194/egusphere-2024-989-AC1
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AC1: 'Reply on CC2', Johannes Reinthaler, 25 Jun 2024
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CC3: 'Comment on egusphere-2024-989', Renato R. Colucci, 18 Jun 2024
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I read this work with interest, as it certainly represents a necessary contribution to the better understanding of glacial evolution in perhaps the most studied mountain sector in the world when dealing with mountain glaciers. Nonetheless, my view is that the uncertainties of assessment that a work of this type inevitably entails could have been minimized by wider cooperation. In a mountain chain as deeply studied as the Alps, the individual specificities of the various Alpine sectors are certainly clearer locally.
After this general comment, I will go into the specifics of the area of my major competence. Particularly, on line 163 and in several figures, I may disagree with the subdivision of area 13, as it would be more correct to indicate Dolomites and Julian Alps, instead of Carnic Alps. In fact, in the Carnic Alps there is only one documented glacier in Austria, the Eiskar Glacier.
I might suggest also reading and citing the following as it represents the first detailed inventory of the LIA Julian Alps glaciers with the first details on what in this preprint is discussed at paragraphs 3.1, and 4
Colucci R.R. (2016). Geomorphic influence on small glacier response to post Little Ice Age climate warming: Julian Alps, Europe. Earth Surface Processes and Landforms, 41: 1227-1240
http://onlinelibrary.wiley.com/doi/10.1002/esp.3908/abstractCitation: https://doi.org/10.5194/egusphere-2024-989-CC3 -
AC3: 'Reply on CC3', Johannes Reinthaler, 26 Jun 2024
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The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-989/egusphere-2024-989-AC3-supplement.pdf
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AC3: 'Reply on CC3', Johannes Reinthaler, 26 Jun 2024
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