Le glacier Jamtal en Autriche, la scientifique Andrea Fischer le connaît comme sa poche. Mais jamais « elle n’aurait imaginé qu’il fonde de manière aussi spectaculaire que cet été », emportant dans le processus des données précieuses.
Au fil du réchauffement climatique, « nos archives disparaissent », s’inquiète-t-elle, tout en examinant à ses pieds la glace qui, à certains endroits, se mêle à la terre, donnant au paysage un aspect grisâtre. Depuis plus de 20 ans, Mme Fischer scrute à la loupe Jamtal et d’autres glaciers de la région montagneuse du Tyrol.
Dans ces capsules temporelles uniques, permettant de remonter à des milliers d’années, elle et son équipe prélèvent régulièrement des carottes de glace. Ils peuvent ensuite les dater en procédant à des mesures de carbone 14 sur des débris végétaux restés emprisonnés à travers le temps.
L’analyse des différentes couches permet de « comprendre le climat du passé et de créer des modèles pour l’avenir », explique la chercheuse. Une tâche qui devient toutefois de plus en plus complexe pour la directrice adjointe de l’Institut de recherche sur la montagne d’Innsbruck, rattaché à l’Académie des Sciences. Car la fonte, indicatrice du changement climatique, s’est accélérée ces 20 dernières années, selon une étude publiée dans Nature en avril 2021. Sur les 220.000 glaciers de la planète, les 4.000 localisés dans les Alpes ont particulièrement rétréci et la plupart sont voués à s’évaporer.
« Cette année est insensée en comparaison de la moyenne des 6.000 dernières années », lance Andrea Fischer. « À ce rythme, Jamtal ne sera plus un glacier dans cinq ans. » Elle a même dû avancer de quelques jours une opération de forage à 14 mètres de profondeur, devant les températures exceptionnellement élevées. En temps normal, la neige protège le glacier du soleil pendant l’été, mais le peu de flocons tombés l’hiver dernier avait déjà disparu début juillet.
« Le glacier est donc entièrement exposé au soleil pendant deux mois », souligne la scientifique. L’impact pour la recherche est dévastateur: Mme Fischer pronostique une perte de sept mètres de glace cette année, contre un mètre habituellement, « ce qui correspond à l’analyse de 300 ans de changement climatique » partie en fumée.
La situation engendre en outre des risques supplémentaires du fait des vagues de chaleur qui rendent les terrains instables – comme au glacier de la Marmolada en Italie, où un énorme bloc s’est effondré en juillet, tuant onze personnes.
Sans oublier les autres répercussions: au-delà de leur rôle économique vital pour attirer les touristes, les glaciers autrichiens alimentent en été les grandes rivières et contribuent au réseau hydraulique.
Au village voisin de Galtür, qui compte 870 habitants, le club alpin a pris les devants et propose déjà une randonnée intitulée « Goodbye, glacier! » pour tenter de susciter une prise de conscience autour du réchauffement.
Sa responsable Sarah Mattle évoque un sentiment de « gravité » des visiteurs « quand ils prennent réellement conscience de ce qu’ils entendent et voient dans les médias ».
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Glaciologists Andrea Fischer (R) and Violeta Lauria from the Austrian Academy of Sciences measure the height under a part of the ice shelf of the Jamtal Glacier (Jamtalferner) near Galtuer, Tyrol, Austria on July 20, 2022. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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Glaciologists Andrea Fischer (L) and Violeta Lauria from the Austrian Academy of Sciences walk on the Jamtal Glacier (Jamtalferner) near Galtuer, Tyrol, Austria on July 20, 2022. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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Glaciologist Andrea Fischer from the Austrian Academy of Sciences looks at ice samples from the Jamtal Glacier (Jamtalfern) near Galtuer in Innsbruck Tyrol, Austria on July 20, 2022. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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A photo taken on July 20, 2022 shows the Jamtal Glacier (Jamtalferner) near Galtuer, Tyrol, Austria. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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A photo taken on July 20, 2022 shows the Jamtal Glacier (Jamtalferner) near Galtuer, Tyrol, Austria. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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A photo taken on July 20, 2022 shows the Jamtal Glacier (Jamtalferner) near Galtuer, Tyrol, Austria. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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Glaciologists Andrea Fischer (R) and Violeta Lauria from the Austrian Academy of Sciences measure the height under a part of the ice shelf of the Jamtal Glacier (Jamtalferner) near Galtuer, Tyrol, Austria on July 20, 2022. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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Glaciologists Andrea Fischer (L) and Violeta Lauria from the Austrian Academy of Sciences walk on the Jamtal Glacier (Jamtalferner) near Galtuer, Tyrol, Austria on July 20, 2022. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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Glaciologist Andrea Fischer from the Austrian Academy of Sciences looks at ice samples from the Jamtal Glacier (Jamtalfern) near Galtuer in Innsbruck Tyrol, Austria on July 20, 2022. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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A photo taken on July 20, 2022 shows the Jamtal Glacier (Jamtalferner) near Galtuer, Tyrol, Austria. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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A photo taken on July 20, 2022 shows the Jamtal Glacier (Jamtalferner) near Galtuer, Tyrol, Austria. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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A photo taken on July 20, 2022 shows the Jamtal Glacier (Jamtalferner) near Galtuer, Tyrol, Austria. – Jumping from rock to rock to cross a creek gushing down Austria’s Jamtal glacier, scientist Andrea Fischer worries that precious research opportunities will be irreversibly lost as the snow and ice melt faster than ever. The Jamtal glacier has been losing about one metre (three feet) from its surface annually, but this year it has already lost more than a metre. (Photo by KERSTIN JOENSSON / AFP)
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