Glaciers reveal Southern Alps climate change

An annual monitoring flight over 48 Southern Alps glaciers revealed that summer snow lines are the highest for two decades. This, say researchers at the National Institute of Water and Atmospheric Research (NIWA), is the third year in a row in which the glaciers have lost ice mass, suggesting the Southern Alps’ climate shifted abruptly in 1998.

“If that is so, it means glaciers like the Fox and Franz Josef can be expected to shrink over the next few years, as changes in the upper snow field are reflected further down the glaciers,” said Senior NIWA Climate Scientist, Dr Jim Salinger.

Meanwhile, the International Commission for Snow and Ice has warned that the Himalayas’ 15,000 glaciers are melting faster than any other glacier group and that they could disappear entirely by the year 2035 (see related story). Receding glaciers in tropical areas of South America and Africa are also causing concern.

The New Zealand researchers say the height of the Southern Alps glacier snowline at the end of summer revealed how much snow the glaciers have gained during the past year. The higher the glacier snowline, the less the amount of snow that has accumulated to feed the glacier. Over the past two decades the glacier snow lines have been lower down the mountains, and this additional snow has thickened the glaciers.

“After a few years delay for the time it takes the extra snow to flow down to the glacier terminus, the glaciers have generally been growing” said glaciologist Trevor Chinn. “Since 1998, however, the snowlines have been high and the glaciers will begin to shrink.”

Dr Salinger said that even though last winter’s snowfalls in the Southern Alps were average, 1999 produced unusual weather for the South Island, with the greatest number of anticyclones on record, fewer westerly winds from the Roaring Forties, and a drier summer than usual. It was also the warmest year on record in the Southern Alps. All these factors contributed to the highest glacier snow lines on record.

“They all fit comfortably with a marked climate shift in 1998,” Dr Salinger said, “but it’s a long term trend. These climate shifts can last for several decades. We won’t really know if we are properly into it for another two or three years.”