Le Grand dégel, du Groenland à l’Antarctique

Version anglaise=> « The Big Thaw »:  dans le magazine National Geographic – Juin 07

Du Groenland à l’Antarctique, la planète perd sa glace plus vite que l’on puisse se l’imaginer. Est-ce que l’humain peux en diminuer sa croissance? 

« …JUST AS JAKOBSHAVN ACCELERATED, its tongue—the glacier’s seaward end, floating on the waters of the fjord—began to shatter and retreat. Since 2000, the tongue has receded by four miles (six kilometers), adding to the clutter of icebergs in the fjord. Many of the other Greenland glaciers racing to the sea have also lost part or all of their tongues, which may explain the speedup. « Floating ice acts as a buttress, » explains Abdalati. « It holds back the ice behind it, so that when it melts, it sort of uncorks the glacier. »

Greenland’s weather has warmed palpably. Winter temperatures at Steffen’s ice camp have risen about five degrees Celsius (9°F) since 1993. In the past, researchers riding snowmobiles to outlying instrument stations could still count on firm snow as late as May; last year they got stuck in slush. For the past two years Ilulissat—well above the Arctic Circle, a place where street signs mark dogsled crossings—has had long winter thaws. « It was supposed to be minus 20 (-29ºC), » says Steffen, « and instead it was raining…. »

The latest signs from Greenland have persuaded many ice researchers that sea level could rise three feet (one meter) by 2100. Rignot, who has measured the rush of glaciers to the sea, says even that figure may turn out to be an underestimate. Greenland, he notes, could ultimately add ten feet (three meters) to global sea level, « and if this happens in the next hundred years instead of the next several hundred years, that’s a very big deal… »

Acheter l’édition du National Geographic de juin 07 afin de lire le dossier complet…plus d’info >>