Scientists use powerful techniques to visualize effects of dust particles on cloud formations.
An international team led by Japanese scientists has generated significant findings that highlight the impact of high-latitude dusts on the conversion of clouds' water droplets to ice - or glaciation - within low-level clouds in the Arctic region. These results contribute to a better understanding of factors at the land surface and how they affect cloud formations. The research findings also add to a better understanding of how climate is affected by clouds, which are increasingly considered to be among the most important -- yet complex -- regulators of the global climate. Depending on the conditions, clouds either enhance warming or help cool the climate by trapping heat or reflecting sunlight back into space, respectively.
The study was published in Nature Geoscience on March 25, 2019 (12:00 US Eastern time).
Clouds play one of the most important roles in the atmospheric system. They are key players in maintaining the radiation balance of the Earth's atmosphere and are also involved in maintaining the Earth's energy equilibrium. They are made up of particles such as ice crystals and/or droplets that in turn mediate the atmosphere's radiation balance and the maintenance of the Earth's energy equilibrium. When chilled below 0oC, water molecules start forming ice crystals wherever there are minerals or other solids suspended in the water--what are known as nucleation sites. Completely pure water that has no nucleation sites can be chilled well below the usual freezing point and yet remain a liquid--a process called supercooling. Clouds can also be affected by dust particles as they serve as ice nucleating particles (INPs) and cloud condensation nuclei (CCN) allowing ice and liquid droplet formation. In particular, mixed-phase clouds that are made up of water and ice are especially sensitive to dust particles whose source is yet to be fully elucidated.
Image caption: The glacier Brøggerbreen and its surroundings in July 2016 which show the characteristics of glacial outwash sediments obtained in Svalbard.
Image credit: Yutaka Tobo, Ph.D., the National Institute of Polar Research, Japan.
Research to date has mostly focused on arid and semi-arid regions in low-mid altitudes as sources of dust. However, recent findings suggest that dust particles can also originate from ice- and vegetation free areas in high altitudes, thereby begging the question of whether these particles have the same effect on cloud nucleation as those coming from other regions. Specific to this study, the researchers considered dust coming from regions of glacial outwash plains, or regions of deposits of sand and gravel carried by running water from the melting ice of a glacier and laid down in deposits. In fact, these regions are thought to be a major source of wind-blown dusts in cold, high latitudes.
"We found that dusts derived from glacial outwash plains can serve as very efficient nuclei for ice nucleation, as compared with desert mineral dusts. This is because of the presence of small amounts of organic matter having very high ice nucleating ability" says corresponding author Yutaka Tobo, Ph.D. an assistant professor at the National Institute of Polar Research. "Our field experiments and model simulations further suggest that such glacially sourced dusts may contribute significantly to ice nucleation in Arctic low-level clouds, especially during summertime," Dr. Tobo adds.
In the future, the researchers hope to expand their findings by performing additional investigations. "Recent studies have shown that significant dust emissions can also occur in Greenland, North America and Iceland, and we are not yet sure about the ice nucleating ability of dusts released from these high-latitude sources. In addition, it is expected that the recent rapid and widespread retreat of glaciers may lead to more active dust emissions from high-latitudes in the future. Therefore, further comprehensive studies will be necessary to understand the possible impact of high-latitude dusts on current and future aerosol-cloud-precipitation interactions in the Arctic, which is more sensitive to climate change than any other region of the world."
This research was partially supported by JSPS KAKENHI grants, the Arctic Challenge for Sustainability (ArCS) Project and the Environment Research and Technology Development Fund of the Environmental Restoration and Conservation Agency, NSF grants, DOE SciDAC and Cornell University's David R. Atkinson Center for a Sustainable Future.
The article
"Glacially sourced dust as a potentially significant source of ice nucleating particles" recently appeared in Nature Geoscience and is available at
DOI: 10.1038/s41561-019-0314-x
Authors
Yutaka Tobo, Kouji Adachi, Paul J. DeMott, Thomas C. J. Hill, Douglas S. Hamilton, Natalie M. Mahowald, Naoko Nagatsuka, Sho Ohata, Jun Uetake, Yutaka Kondo & Makoto Koike
About Nagoya University
Nagoya University has a history of about 150 years, with its roots in a temporary medical school and hospital established in 1871, and was formally instituted as the last Imperial University of Japan in 1939. Although modest in size compared to the largest universities in Japan, Nagoya University has been pursuing excellence since its founding. Six of the 13 Japanese Nobel Prize-winners since 2000 did all or part of their Nobel Prize-winning work at Nagoya University: four in physics - Maskawa and Kobayashi in 2008, and Akasaki and Amano in 2014 - and two in Chemistry - Noyori in 2001 and Shimomura in 2008. In mathematics, Mori did his Fields Medal-winning work at Nagoya University. A number of other important discoveries have been made at Nagoya University, including the Okazaki DNA Fragments by Reiji and Tsuneko Okazaki in the 1960s; and depletion forces by Asakura and Oosawa in 1954.
In addition, Nagoya University currently engages in research and educational programs aimed at helping developing countries in Africa and Asia improve food security, nutrition and environmental conservation. For example, Nagoya University researchers have potentially solved the striga (witchweed) problem, which causes $13 billion damage annually in Africa to food crops like maize and sorghum. Field tests are now underway in Kenya. In Asia, local farmers are being trained by Nagoya University researchers in growing food crops more sustainably. And new rice varieties have been developed at Nagoya University that can feed more people and thereby reduce food scarcity in developing countries. Many other such programs are currently being undertaken by Nagoya University researchers.
About Nagoya
Nagoya is Japan's fourth-largest city with 2.2 million residents and third-largest metropolitan area after the Tokyo and Osaka urban areas. Nagoya's surrounding Aichi Prefecture has led Japan in industrial output since 1977. Greater Nagoya produces 51.7% of Japan's total automobile output and 45% of the country's auto parts. This represents 8.2% of global automobile production. The Greater Nagoya Area produces 27% of Japan's manufacturing output (versus 11% in Greater Tokyo and 10.2% in Greater Osaka) and 24% of Japan's exports. The Greater Nagoya area is the hub of Japanese manufacturing industries, producing over 40% of major manufacturing categories such as automobiles, automobile parts, machine tools and aircraft parts. The Greater Nagoya GDP is $US461 billion, as a country it would be 22nd in the world, below Poland and above Belgium. (Japanese Cabinet figures, 2015.) Nagoya Port is Japan's largest in terms of import and export tonnage and in terms of export value.
