Record ice melt in Southern Alps
Climate change a factor in dramatic loss, says scientist
The hottest summer on record drove the biggest seasonal melt ever recorded at the Southern Alps, says Dr Jim Salinger. The veteran climate scientist, who gave a presentation to a meteorology conference in Christchurch yesterday, has described the mountain range as a “canary in the coalmine”, due to the sensitivity of its postcard glaciers to climate change.
New Zealand’s glaciers have been losing ice since annual snowline surveys began 40 years ago — a trend that had been in step with rising average sea surface temperatures around the country.
But the summer of 2017/18, which broke an 84-year-old record for warmth, had hit them particularly hard.
During the usual melt season on the Southern Alps, running from November to March, temperatures had been 2.2C above normal.
This had been coupled with many highs passing over the region, along with a very unusual lack of westerly winds.
At the same time, a marine heatwave that engulfed New Zealand’s waters pushed sea surface temperatures to between 2.5C and 4C above average through much of December last year. Incredibly, some localised spots off the West Coast even reached between 4C and 6C above normal. Salinger, speaking at the hydrological and meteorological societies’ joint conference yesterday, estimated the total ice volume loss for the 2018 glacier year was 3.76 cubic km of water equivalent.
That was about 9 per cent of the alps’ total ice volume — and the greatest annual loss on record. But he told the Herald he was not surprised at this result.
“With the warmth, clear skies and lack of weather patterns that produce snow, this was ideal for much melt of glacier ice.”
One recent study suggested New Zealand’s total glacier area had shrunk from 1240sq km to 857sq km since the late 1970s — a decrease of 31 per cent.
Salinger said some of last summer’s records could be attributed to climate change, because this had driven warmer sea temperatures, along with a positive Southern Annular Mode.
“Our alps are the canary in the coalmine for anthropogenic warming because the glaciers are very sensitive to higher temperatures and changed weather patterns in the melt season expected with climate change.”
Around the world, glaciers were already melting at an unprecedented rate, losing on average between half a metre and a metre of ice thickness every year.