How sea salt aerosols are affecting Arctic climate change

Recent reports have indicated how temperatures in the Arctic continue to rise at three to four times the global annual average. Now, in a new study, researchers have found how fine sea salt aerosols produced under blizzardy, or blowing snow, conditions contribute to Arctic warming.

Measurements from a yearlong drift in sea ice across the Central Arctic show that large amounts of fine sea salt particles are produced during blowing snow events, affecting cloud properties and warming the surface, an article published on Nature.com explains. The study was published in the journal Nature Geoscience on 4 September.

Scientists have known for a long time that pollutants from other regions can accumulate in the Arctic atmosphere, where they alter atmospheric chemistry, absorb sunlight, and affect local weather patterns. This leads to localized warming that melts ice and snow. According to a press release from the Washington University in St. Louis, sea salt particles dominate aerosol mass concentration, but their production mechanisms and impact on Arctic climate have remained unclear.

In the study, the researchers used a global chemical transport model to estimate that from November to April north of 70° N, sea salt aerosol produced from blowing snow accounted for about 27.6% of the total particle number, and the sea salt aerosol increased the longwave emissivity of clouds, leading to a calculated surface warming of +2.30 W m−2 under cloudy sky conditions, the article on Nature.com explains.

According to the press release, atmospheric scientists, led by Jian Wang, director of the Center for Aerosol Science and Engineering (CASE) and professor of energy, environmental & chemical engineering in the McKelvey School of Engineering at Washington University in St. Louis, investigated the production and impact of sea salt aerosols on Arctic warming. Wang’s team analyzed data collected by the Multidisciplinary drifting Observatory for the Study of Arctic Climate (or MOSAiC), the press release from the Washington University in St. Louis adds.

“The MOSAiC expedition let us observe how aerosols and clouds evolve over the course of a year and led to this discovery," Wang said in the press release. “Sea salt particles in the Arctic atmosphere aren’t surprising, since there are ocean waves breaking that will generate sea salt aerosols. But we expect those particles from the ocean to be pretty large and not very abundant. We found sea salt particles that were much smaller and in higher concentration than expected when there was blowing snow under strong wind conditions," Wang said. “Model simulations that don’t include fine sea salt aerosols from blowing snow underestimate aerosol population in the Arctic," Wang said in the release.

With this observational confirmation and systematic study, which revealed that sea salt particles produced from blowing snow account for about 30% of total aerosol particles, climate models can now be updated to include the effects of these fine particles, the release explains.

(With inputs from peer-reviewed scientific publications)

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