Bacteria may have key role in Arctic weather

Scientists have identified a surprising new mechanism that could be affecting cloud formation and weather patterns in the Arctic – bacteria from the ocean floor.

When tiny, plant-like ocean microbes known as phytoplankton die, their bodies sink to the bottom of the sea, becoming food for bacteria residing there. New observations made in the Bering and Chukchi seas off the coast of Alaska suggest that under the right conditions, these algae eaters are sloshed to the surface, and from there, wafted into the air.

Once airborne, seafloor bacteria may become seeds that promote the growth of ice crystals, an important step in the formation of Arctic clouds.

‘‘Clouds are super-important in the Arctic,’’ said Jessie Creamean, an atmospheric scientist at Colorado State University and lead author of new research published in Geophysical Research Letters.

‘‘They regulate the surface and atmospheric temperatures, affecting sea ice, ecology, shipping, Arctic climate and weather. And we just have a really poor understanding of how they form.’’

Prior research from the Southern Ocean as well as laboratory experiments suggest that ocean microbes can enhance cloud formation.

To investigate whether that holds true in the Arctic, Creamean and several of her co-authors embarked on a National Oceanic and Atmospheric Administration (NOAA)-funded research cruise through the Bering and southern Chukchi seas from late August to mid-September 2017. Over several weeks, they collected samples of seawater and aerosols suspended about 20 metres above the ship.

They measured the abundance of so-called icenucleating particles, which seed clouds. They also took stock of seawater chemistry and chlorophyll concentrations, an indicator of phytoplankton abundance.

At first, Creamean said, she was simply hoping to get a baseline sense of the distribution of cloudseeding particles in the ocean and atmosphere. But on August 29, as their ship passed through the Bering Strait, the researchers measured particularly high levels of them.

Through a combination of DNA analysis and microbial culturing, they determined that the airborne particles were mostly bacteria.

The researchers knew that there was a big latesummer phytoplankton bloom under way about 240 kilometres to the south, and that they were in a region where phytoplankton transported north via currents tend to die, sink and become food for hungry bacteria.

After examining oceanographic measurements and running their data through computer models, the researchers concluded that powerful winds associated with recent storm activity had stirred up the ocean, bringing some of the bacterial grazers to the surface, where they could be kicked up into the air.

The study doesn’t actually demonstrate that bacteria are forming clouds, simply that they’re making it into the atmosphere. But Creamean feels it’s a distinct possibility that some oceanic bacteria are reaching high enough altitudes to play a role in cloud formation.

‘‘In the Arctic, clouds can be very low – down to 100 metres,’’ she said. ‘‘It’s very possible these things can interact with clouds.’’

Over the years, studies have suggested that microbes and their debris can brighten clouds, supercharge snowstorms, and help to create some of the biggest hail events.

With the advent of new genomic tools, scientists are learning that there are entire microbial ecosystems wafting through the lower atmosphere,