Andrew Lorrey, Andrew Mackintosh and Brian Anderson
Every March, glacier ‘watchers’ take to the skies to photograph snow and ice clinging to high peaks along the length of New Zealand’s Southern Alps.
This flight needs to happen on cloud-free and windless days at the end of summer before new snow paints the glaciers white, obscuring their surface features.
Fox Glacier’s spectacular retreat from Brian Anderson on Vimeo.
Summer of records
The summer of 2017-18 was New Zealand’s warmest on record and the Tasman Sea experienced a marine heat wave, with temperatures up to six degrees above normal for several weeks.
The loss of seasonal snow cover and older ice during this extreme summer brings the issue of human-induced climate change into tight focus.
The annual flights have been taking place for four decades and the data on end-of-summer snowlines provide crucial evidence.
The disappearance of snow and ice for some of New Zealand’s glaciers is clear and irreversible, at least within our lifetimes.
Many glaciers that we survey now will simply vanish in the coming decades.
Embellishing our landscape
Glaciers are a beautiful part of New Zealand’s landscape, and important to tourism, but they may not be as prominent in the future.
This stored component of the freshwater resource makes contributions to rivers that are used for recreation and irrigation of farm land.
Meltwater flowing from glaciers around Aoraki/Mt Cook into the Mackenzie Basin feeds important national hydroelectricity power schemes.
Seasonal meltwater from glaciers can partially mitigate the impacts of summer drought.
This buffering capacity may become more crucial if the eastern side of New Zealand’s mountains become drier in a changing climate.
New insights from old observations
The Southern Alps end-of-summer snowline photo archive, produced by the National Institute of Water and Atmospheric Research, is a remarkable long-term record.
Glaciers respond to natural variability and human-induced changes, and we suspect that the latter has become more dominant for our region.
During the 1980s and 1990s, while glaciers were largely retreating in other parts of the world, many in New Zealand were advancing.
Our recent research shows this anomaly was caused by several concentrated cooler-than-average periods, with Southern Alps air temperature linked to Tasman Sea temperatures directly upwind.
The situation changed after the early 2000s, and we postulated whether more frequent high snowlines and acceleration of ice loss would occur.
Since 2010, multiple high snowline years have been observed. In 2011, the iconic Fox Glacier (Te Moeka o Tuawe) and Franz Josef Glacier (Ka Roimata o Hine Hukatere) started a dramatic retreat – losing all of the ground that they regained in the 1990s and more.
Andrew Lorrey is Principal Scientist & Programme Leader of Climate Observations and Processes at the National Institute of Water and Atmospheric Research (NIWA). Andrew Mackintosh is Professor & Director of Antarctic Research Centre and an expert on glaciers and ice sheets, and Brian Anderson is a Senior Research Fellow, both at the Victoria University of Wellington. The above is a highly edited version. For full text, please visit our website www.indiannewslink.co.nz
*
Photo Caption:
- The Franz Josef glacier advanced during the 1980s and 1990s but is now retreating.
(Picture by Andrew Lorrey for NIWA, CC BY-SA)
- Fox Glacier: Video by Victoria University https://vimeo.com/119312940
