A deep learning reconstruction of mass balance series for all glaciers in the French Alps: 1967–2015

• Main Authors: J. Bolibar, A. Rabatel, I. Gouttevin, C. Galiez
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-09-01
• Series: Earth System Science Data
• Online Access: https://essd.copernicus.org/articles/12/1973/2020/essd-12-1973-2020.pdf

<p>Glacier mass balance (MB) data are crucial to understanding and quantifying the regional effects of climate on glaciers and the high-mountain water cycle, yet observations cover only a small fraction of glaciers in the world. We present a dataset of annual glacier-wide mass balance of all the glaciers in the French Alps for the 1967–2015 period. This dataset has been reconstructed using deep learning (i.e. a deep artificial neural network) based on direct MB observations and remote-sensing annual estimates, meteorological reanalyses and topographical data from glacier inventories. The method's validity was assessed previously through an extensive cross-validation against a dataset of 32 glaciers, with an estimated average error (RMSE) of 0.55&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="11a39eed12cc43bd042b7c6ff52fbf8b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00001.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00001.png"/></svg:svg></span></span>, an explained variance (<span class="inline-formula"><i>r</i>²</span>) of 75&thinsp;% and an average bias of <span class="inline-formula">−0.021</span>&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="1229264da99210480fe6fe0c014f08dc"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00002.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00002.png"/></svg:svg></span></span>. We estimate an average regional area-weighted glacier-wide MB of <span class="inline-formula">−0.69</span><span class="inline-formula">±</span>0.21 (1<span class="inline-formula"><i>σ</i></span>)&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="38c7ed2845b2ac6949b4d2ac7360cf0e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00003.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00003.png"/></svg:svg></span></span> for the 1967–2015 period with negative mass balances in the 1970s (<span class="inline-formula">−0.44</span>&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="1b8e74d2586fe2cece3ef01f194d2b4d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00004.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00004.png"/></svg:svg></span></span>), moderately negative in the 1980s (<span class="inline-formula">−0.16</span>&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="95942ab676b01b8d7c87e30889e73273"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00005.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00005.png"/></svg:svg></span></span>) and an increasing negative trend from the 1990s onwards, up to <span class="inline-formula">−1.26</span>&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="128ea6924615ac3e42cea2b6c9659a75"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00006.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00006.png"/></svg:svg></span></span> in the 2010s. Following a topographical and regional analysis, we estimate that the massifs with the highest mass losses for the 1967–2015 period are the Chablais (<span class="inline-formula">−0.93</span>&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="b9db93df1dcea70fe016d2815062ab83"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00007.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00007.png"/></svg:svg></span></span>), Champsaur (<span class="inline-formula">−0.86</span>&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="e9f580d8aa897f340b637c81feb72e0a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00008.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00008.png"/></svg:svg></span></span>), and Haute-Maurienne and Ubaye ranges (<span class="inline-formula">−0.84</span>&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="020b277a95eece962586b3549238e683"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00009.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00009.png"/></svg:svg></span></span> each), and the ones presenting the lowest mass losses are the Mont-Blanc (<span class="inline-formula">−0.68</span>&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="5f37048e66695ea6e950532225bb3500"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00010.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00010.png"/></svg:svg></span></span>), Oisans and Haute-Tarentaise ranges (<span class="inline-formula">−0.75</span>&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M24" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">w</mi><mo>.</mo><mi mathvariant="normal">e</mi><mo>.</mo><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">a</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="49pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="c9a9bf02b777c0213ae832d6e668e670"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-12-1973-2020-ie00011.svg" width="49pt" height="13pt" src="essd-12-1973-2020-ie00011.png"/></svg:svg></span></span> each). This dataset – available at <a href="https://doi.org/10.5281/zenodo.3925378">https://doi.org/10.5281/zenodo.3925378</a> <span class="cit" id="xref_paren.1">(<a href="#bib1.bibx5">Bolibar et al.</a>, <a href="#bib1.bibx5">2020</a><a href="#bib1.bibx5">a</a>)</span> – provides relevant and timely data for studies in the fields of glaciology, hydrology and ecology in the French Alps in need of regional or glacier-specific annual net glacier mass changes in glacierized catchments.</p>