A new study by Nagoya University has revealed that dust from snow- and ice-free areas of the Arctic may be an important contributor to Arctic warming.
Previous studies have theorised that Arctic warming leads to the region’s clouds containing more liquid droplets and fewer ice crystals. As a result, this might cool the region during summer.
However, the new study showed that as the Arctic warms, snow- and ice-free areas increase, leading to an increase in dust emissions. The dust promotes the formation of ice crystals in the clouds.
The Arctic is warming at an alarming rate
The Arctic is warming much faster than the rest of the world, a phenomenon known as ‘Arctic amplification’.
Arctic temperatures are rising at least three times faster than the global average. In 2023, the Arctic experienced its warmest summer ever recorded.
Some factors that contribute to the amplification of Arctic warming include:
- Less snow and ice: Snow and ice reflect sunlight, so when they melt, more sunlight is absorbed by the ocean, which warms the ocean and atmosphere.
- Less convection: In the Arctic, less sunlight reaches the surface, so the atmosphere is heated by moist air from the tropics. This results in less convection and vertical mixing.
- Greenhouse gases: Carbon dioxide and other greenhouse gases mainly affect the atmosphere near the surface.
The effects of Arctic warming are felt across the high latitudes and beyond, and have global environmental, economic, and social implications.
Debunking previous understandings of ice crystal changes
Mixed-phase clouds, which consist of both liquid droplets and ice crystals, are ubiquitous in Earth’s atmosphere and have substantial impacts on Earth’s cloud radiative balance, precipitation, and hydrological cycle.
These clouds are particularly abundant in the lower troposphere of the Arctic region, where warming is proceeding at a rate two to four times faster than the global average
It is possible that more ice crystals in the clouds are making the clouds thinner and shorter-lived, therefore reflecting less sunlight, which might heat the region during summer (emission feedback).
“Increasing amounts of dust due to Arctic warming may cause the opposite phenomenon of the conventional understanding of ice crystal changes,” explained Associate Professor Hitoshi Matsui of Nagoya University, the lead author of the study.
“Our previous study found that a large amount of Arctic dust is distributed in the lower troposphere (below about 3 km altitude) over the region in summer and early fall, with the dust acting as a very efficient nucleus for ice formation in clouds at this altitude during the season.”
How Arctic warming and dust levels are connected
To estimate the impact of Arctic dust on the region’s clouds, Matsui and Dr Kei Kawai of Nagoya University, in collaboration with researchers from the National Institute of Polar Research and Hokkaido University, conducted a study using the CAM-ATRAS global aerosol-climate model.
They first looked at changes in the amount of dust released from the Arctic land surface over the past 40 years, between 1981 and 2020.
The simulations showed that dust emissions increased by 20% during this period as Arctic warming increased.
This increase promotes ice nucleation in clouds in the lower troposphere, weakening the efficiency of clouds to contain more liquid droplets and fewer ice crystals as the Arctic warms.
Increased dust levels promote ice crystal formation, outweighing the decrease in ice crystal formation by the temperature feedback in 30% of the region annually and 70% in summer.
“Most climate models have not considered the effects of dust from the Arctic land surface,” Matsui said.
“Our research suggests that the counterbalancing temperature and emission feedbacks should be considered to improve the accuracy of climate change predictions in the Arctic.”
