In the summer of 2019–2020, New Zealand’s Southern Alps experienced an unusual phenomenon: the pristine white snow turned a vivid red. Initially attributed to ash from Australia’s devastating bushfires, subsequent research revealed a different cause.
The True Culprit: Australian Desert Dust
A comprehensive geochemical analysis determined that the red discoloration resulted from massive dust storms in southeastern Australia. These storms transported approximately 4,500 tons of red desert dust across the Tasman Sea, depositing it onto New Zealand’s snowfields. This finding corrected earlier assumptions that bushfire ash was responsible for the red snow.
Climate Change and Future Implications
The occurrence of such dust storms is expected to become more frequent due to climate change. As global temperatures rise, increased aridity in Australia may lead to more intense dust events. When this dust settles on snow, it reduces the surface’s reflectivity (albedo), causing the snow to absorb more heat and melt faster. This accelerates glacial retreat, posing a significant threat to New Zealand’s alpine ecosystems.
The Role of Snow Algae
In addition to dust, certain microorganisms contribute to the red coloration of snow. Species like Chlamydomonas nivalis and Chlainomonas kolii produce red pigments that can tint snow pink or red, a phenomenon known as “watermelon snow” or “glacier blood.” These algae thrive in cold, nutrient-rich environments and can further decrease snow albedo, exacerbating melting.
Conclusion
The red snow in New Zealand’s Southern Alps serves as a stark reminder of the interconnectedness of environmental systems. Transcontinental dust transport and microbial activity, both influenced by climate change, can have profound effects on distant ecosystems. Understanding these processes is crucial for predicting and mitigating the impacts of a warming planet.
