While it may look like something out of a Dr. Seuss book, these pink glaciers are more than imaginary. In fact, they're right in the heart of the Mount Aspiring National Park and can tell us a fair amount about the future of our climate. Despite their storybook appearance, these local glaciers have a fair amount of science explaining why they have taken this hue. 

There had been some suggestion the phenomena was just watermelon snow, also called snow algae, which is caused by Chlamydomonas nivalis. However in watermelon snow, the pigment is in the snow and when it melts it looks like port wine. Whereas photographer Liz Carlson reported Mt Aspiring's pink, “was very clearly dirt and dust when you walked on it and touched it.” 

The most widely accepted explanation for the ‘flamingo glaciers' comes from across the ditch. A senior lecturer in earth sciences at the University of Wollongong, Dr. Sam Marx, studied this kind of ‘dust migration science' as part of his PhD. Marx explained the difference between the orange dust in town and the pink lemonade glaciers, “the snow fields appear pink because Australian dust grains are coated in iron — they are essentially rusty. This gives the dust a red/pink colouration when mixed with the snow. In addition to this, there is sometimes a red algae that grows on the ice after the ice has been fertilised by Australian dust or ash. This also has pink colour when mixed with snow.”

Local travel blogger Carlson posted the unusual pink glaciers on their blog early this month after flying with Wānaka Helicopters over the national park, explaining in the post, “as we got closer and closer towards the first of the mighty glaciers, I pulled my sunglasses off to wipe them. Did I see things, or did the snow look, well, a bit red?” Carlson then posed the question, “While I'm no scientist, I wonder if this layer of red will exist in the ice to tell the story of the bushfires in a thousand years? The same way we could see the ash layers from ancient volcanic eruptions around the world now?”

Dr. Andrew Lorrey, a principal NIWA climate scientist explained that, “there are long-term records of fires in ice but they're more prevalent in the Northern Hemisphere… in the Greenland ice sheet.” Despite the signs that dust can leave signs of climate change in the geological record, Lorrey proposed that because glaciers are essentially ‘rivers of ice,' the record of dust in our own local glaciers may be poor, and this is not optimised by rapid climate change. One of New Zealand's most famous glaciers, the Tasman glacier, has been very quickly receding at a rate of 180m per year since 1990. It's terminus, the Tasman Lake, didn't actually exist until 1973. “It's a fast-moving glacier… not like an ice sheet,” explained Lorrey, “because of flow in the glacier it's not likely it will contain a long-term record.” 

However, Marx asserted that there is still hope to at least slow the effects of this intense climate change, and it might even exist in the dust itself, “this dust not only tells about past periods of drought and climate variability, but the dust itself also affects our climate. When it is in the atmosphere, dust blocks solar radiation, so it has a cooling effect. In addition, and very importantly, dust fertilises ecosystems by providing nutrients. Dust supplied nutrients are especially important for phytoplankton in the Southern Ocean, which are otherwise lacking in iron —  which the dust supplies. Phytoplankton suck carbon out of the atmosphere as they photosynthesise, then once the phytoplankton die that carbon is deposited on the ocean floor. This process is thought to be very important in regulating Earth's climate, with increased dust production in the past linked to periods of climate cooling. Therefore because dust affects climate we need to quantify dust emissions to be able to understand how Earth's climate has changed in the past and how it will change in the future.”

Since Wānaka resident Liz Carlson published the images on her blog, the story has gone viral across multiple news channels across the world.