New Zealand glaciers critical for water resources and tourism
Glaciers have long been of scientific interest as sensitive indicators of climate change - but we are now starting to realise how important they are for economic reasons too.
Glaciers and snow are an important part of our mountain landscapes from an aesthetic and recreational perspective, but also have a large economic impact, through winter sports, tourism, water resources and hydroelectric power production. For example, the spectacular 1.5 km advance of Franz Josef and Fox glaciers from 1983 to 2008, and subsequent rapid retreat, had a fundamental impact on glacier guiding, with guided tours on foot being replaced with helicopter-only access since 2012. The cause of this spectacular and globally anomalous advance was obscure – in a warming world, why did glaciers advance?
Our 2017 publication in Nature Communications lead by Andrew Mackintosh and Brian Anderson (ARC) and Andrew Lorrey (NIWA) answered this question by using mathematical modelling to show that most of the advance was due to lower temperatures during two discrete periods in the 1980 and 1990's. The positive mass balances that lead to the advance were closely linked to Tasman Sea surface temperatures.
During 2017 we saw extreme weather conditions across New Zealand with a December drought coinciding with a ‘marine heat wave’ where Tasman Sea temperatures were as much as 6°C warmer than usual. The below-average winter snowpack melted quickly and left only glacier melt to support summer flows in many alpine streams. As a result, southern hydro lake levels were lower than normal, because of the combination of low rainfall and early snow melt. This is an example of the kind of weather patterns that we expect the see in the future, when warmer temperatures will likely lead to shallow snowpacks which melt long before peak demand for irrigation and hydropower, and when glaciers will likely lose mass at a rapid rate. Long term, we expect that water availability in mid to late summer will decrease as glaciers shrink and can no long supply melt water. Quantifying these changes, in ways that are useful for stakeholders, is part of the Deep South National Science Challenge - Our Frozen Water Resources project. We have developed snow and glacier models which are being applied and tested against satellite images of seasonal snow and long-term glacier change, with our partners at NIWA, University of Otago, University of Canterbury, Bodecker Scientific Ltd., and Aqualinc Research Ltd. By early to mid-2019, we will have made new projections of the change in glaciers, snow pack, and water runoff which will be important for New Zealand’s economic future.