Arctic dust was found to be the main source of the particles that form ice crystals

Researchers from the University of Nagoya and the National Institute of Polar Research in Japan have found that dust from land without snow cover in the Arctic is the main source of the particles that form ice crystals in low-level clouds in the Arctic (at altitudes below about 3 km). ) during summer and autumn.

The formation of ice crystals in low-level clouds is thought to affect climate because it can cause ice particles to grow at the expense of liquid droplets and then fall as precipitation, resulting in lower reflectance of sunlight and a shorter cloud life.

“The Arctic is said to be warming two to four times faster than the rate of global warming,” said Dr. Kei Kawai of Nagoya University, first author of the study. “Given the distribution and lifetime of low-level clouds influence climate, our findings may help improve predictions of Arctic climate change.” The researchers published their findings in Geophysics Research Letter.

Dust consists of very small mineral particles from soil or sand. It acts as a nucleus for the formation of ice crystals in clouds. Although most of it is emitted from arid regions at low or middle latitudes, recent studies have shown that dust is also emitted from areas where there is no snow, ice, or vegetation in the Arctic. A previous study showed that Arctic dust serves as an efficient nucleus for forming ice crystals because it contains small amounts of organic matter that has high ice nucleating ability.

“In the Arctic, most of the dust is released in the summer through early fall, when surface temperatures are high and snow cover is low,” Kawai said. “In this season, Arctic dust is dispersed in the lower Arctic troposphere (lower than an altitude of about 3 km), where temperatures are warmer than around –15°C. In general, dust particles from deserts at low or middle latitudes do not work efficiently as nuclei to form ice crystals at temperatures warmer than –15°C. In contrast, Arctic dust particles can act as nuclei between –20°C and –5°C due to their high ice nucleating ability.”

However, until recently, the importance of the high nucleating ability of Arctic dust ice remained unclear as it was not considered in any modeling studies. To address this shortcoming, Associate Professor Hitoshi Matsui and Dr. Kawai from Nagoya University, in collaboration with Associate Professor Yutaka Tobo from the National Institute of Polar Research, conducted research using the CAM-ATRAS global aerosol climate model.

First, they incorporated the recently observed high ice nucleation ability of Arctic dust into their model. Then, they compared simulations that took these capabilities into account with those that did not. The results show that in simulations that take this capability into account, Arctic dust acts efficiently as ice nucleating particles in the Arctic region. The simulations also reproduce observations of ice nucleation particles at several locations in the Arctic. In contrast, in the simulations that didn’t take it into account, Arctic dust barely acted as ice nucleating particles.

The results also show that the number of ice nucleating particles from dust from around the world in the Arctic lower troposphere during summer and autumn increases by more than 100 times given the high ice nucleating ability of arctic dust. In addition, almost all of the ice nucleation particles found came from Arctic dust.

Therefore, the researchers confirmed that Arctic dust plays a dominant role as particle nucleation of ice from dust in Arctic low-level clouds during summer and autumn. “We demonstrate that it is important to fully consider the high nucleating ability of Arctic dust ice to clarify the distribution and origin of ice nucleating particles in the Arctic,” said Dr. Kawai. “We hope these findings will also help us understand what’s going on with Arctic warming and more accurately project future Arctic climate change.”