Effect of Australian bushfire ash on New Zealand’s glaciers may be worse than first thought
29 December 2020
Published by https://www.stuff.co.nz/
AUSTRALIA/NEW ZEALAND – The effect of Australian bushfire ash on New Zealand’s melting glaciers “could be worse than it seems”, a researcher says.
Manaaki Whenua Landcare researcher Phil Novis, based in Canterbury, has been awarded nearly $1 million to study the impact of the Australian bushfires on glacial melting in New Zealand.
His project – Australia burning, NZ melting: impacts of bushfires on NZ glacial environments –will examine glacial melting rates caused by the ash.
“There is a quantity called albedo which is a measure of how much of the incoming light or radiation is reflected off the earth’s surface.
“With perfectly clean snow it’s pretty high – not 100 per cent but pretty high. As soon as we start contaminating the snow with things it drops precipitously.”
The South Island’s glaciers were coated in ash from Australia last summer, smoke from bushfires in New South Wales and Victoria blown the Tasman to leave the likes of Franz Josef’s glacier a shade of caramel brown.
The ash and aerosols responsible would have increased the absorption of radiation and caused the snow to melt faster, Novis said.
“This project is about the effect of that on melting rates. Our glaciers are already melting dramatically, and how much are these kinds of events contributing to that?”
A naturally occurring snow algae also coloured glaciers and snow fields at quite large scales, which similarly had a hand in increasing melting, he said.
“The more water you have the more the algae like it, so there is a spiralling effect there. We also don’t know the effect of the bushfire ash on the algae.
“It might kill them or it might make them grow faster because it contains iron which is a fertiliser so it could be even worse than it seems.”
The research project will begin in March.
New Zealand’s mountain glaciers have shrunk by nearly a third since the 1970s and could be gone by the end of the century unless the country moves quickly towards zero emissions.
In March 2018 the late Trevor Chinn, widely regarded as the godfather of New Zealand glaciology, told the New Zealand Listener the Southern Alps melt was the worst he had seen in the 40 years since he first began monitoring the snow line – the thin boundary between glacial ice and snow – at the end of each summer.
“There are rocks sticking out everywhere – the meltback is phenomenal,” he said.
In the four decades since the first survey, New Zealand’s glaciers have lost a third of their ice. The snow line has moved up by an average of 3.7 metres each year.
Over the coming years and decades, those that remain stand to lose another 50-60 per cent of ice.
The retreat of glaciers also increases the risk of rock fall, making them unsafe for walkers.
Franz Josef lost walking access in 2012, and Fox followed in 2014. Guiding companies switched to relying on helicopters to ferry visitors to higher elevations.
