Il volume dei ghiacciai svizzeri si è dimezzato tra il 1931 e il 2016: è la conclusione di uno studio del Politecnico federale di Zurigo (ETH) e dell'Istituto federale di ricerca per la foresta, la neve e il paesaggio (WSL).
Anche se non tutti i ghiacciai si sono sciolti ogni anno, e negli anni '20 e '80 la massa è addirittura cresciuta in casi isolati, in generale il clima del XX secolo è stato sfavorevole per i ghiacciai. Il fenomeno, inoltre, sta visibilmente accelerando.
Lo studio mostra anche che non tutti i ghiacciai sono stati toccati allo stesso modo dalla contrazione. L'entità dello scioglimento di un ghiacciaio dipende dall'altitudine a cui si trova, da quanto è piatta la lingua del ghiacciaio e da quanto è ricoperta di detriti.
Analizzate 21'700 foto storiche
Per arrivare a queste conclusioni gli esperti si sono avvalsi anche dell'aiuto di 21'700 fotografie scattate tra il 1916 e il 1947. Hanno determinato la superficie dei ghiacciai in due diversi momenti, hanno calcolato le differenze di volume e ricostruito la topografia di tutti i ghiacciai svizzeri per l'anno 1931. Il confronto è stato poi effettuato con i dati degli anni 2000.
Per la prima volta i ricercatori hanno così ricostruito l'evoluzione nell'arco di un secolo. Finora, il quadro dei cambiamenti dei ghiacciai si basava principalmente su osservazioni e misurazioni a lungo termine sul campo e sulle fotografie aeree degli anni successivi al 1960.
Notiziario 16.00 del 22.08.2022 Ghiacciai svizzeri
RSI Info 22.08.2022, 18:19
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