Glaciers lost ice mass in past year
The Southern Alps glaciers monitored annually by NIWA lost ice mass in the year to March 2006.
NIWA has surveyed 50 glaciers for the past 30 years using a small fixed wing aircraft to record the height of the snow line at the end of summer. Principal Scientist Dr Jim Salinger says analysis of photographs taken on this year’s survey in March showed the glaciers had lost much more ice than they had gained during the past glacier year.
This is because much less snow fell in the Southern Alps as a result of more anticyclones over New Zealand, especially over July – December 2005. During this six month period, the anticyclones produced milder and drier conditions. Over winter 2005, temperatures were above average. These conditions produced less snow, especially in winter, and the warmer than normal temperatures for the remainder of the year resulted in early snowmelt.
“This year (2005–06) stands in contrast to the gains that have occurred in the previous three glacier years (2002–03, 2003–04, and 2004–05),” Dr Salinger says.
“The higher the snow line, the more snow has been lost to feed the glacier. On average, the snow line this year was about 50 metres above where it would be to keep the ice mass constant.”
The effects of this past (2006) winter are not included in the survey, but may result in a gain in glacier ice mass by March 2007, depending on conditions over this coming summer.
- Worldwide, glaciers are regarded as a useful indicator of global warming, but New Zealand’s glaciers are more complicated because they have their source in areas of extremely high precipitation. West of the Main Divide in the Southern Alps, more than 10 metres (10,000 mm) of precipitation falls each year as clouds are pushed up over the sharply rising mountain ranges. This means the mass of New Zealand’s glaciers is sensitive to changing wind and precipitation patterns as well as to temperature. So, for example, the glaciers advanced during most of the 1980s and 1990s when the area experienced about a 15% increase in precipitation, associated with more El Ni
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