Quick Dips

Franz Josef: I'm Melting

An annual monitoring flight over 48 Southern Alps glaciers has revealed that the glaciers summer snow lines are the highest they have been for two decades. The higher the glacier snowline, the less the amount of snow that has accumulated to feed the glacier.

Climate Scientist Dr Jim Salinger and glaciologist Trevor Chinn say this was the third year in a row where the glaciers had lost ice mass, suggesting that in 1998 the Southern Alps climate abruptly shifted.

"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," Salinger says.

The level of the glacier snow lines was unrelated to how much snow would fall on the countrys skifields in winter.

The Franz Josef is unusual in that the glacier descends through rainforest forest as it moves down the mountain. However, the grey of the bare schist bedrock could soon be added to the green forests and white ice, as the glacier starts receding.

"The Franz Josef has a patch of rock on its upper icefall which is covered by ice when the glacier is advancing," Salinger notes. "But as the glacier recedes, its trunk thins and the rock is exposed again.

"The patch of rock was last visible about 1978, but has reappeared this summer as the trunk of the Franz Josef has thinned. This heralds a significant recession of the front of the glacier in the next few years."

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," says Chinn. "Since 1998, however, the snowlines have been high and the glaciers will begin to shrink."

Salinger says that even though last winter snowfalls in the Southern Alps were average, 1999 produced unusual weather for the South Island, with the most 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," Salinger says, "but its 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."