18 Nov 2019 - 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, plantlike 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 are 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 mid-July 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,” Creamean said.
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 NOAA-funded research cruise through the Bering and southern Chukchi seas from late August to mid-September 2017. Over the course of several weeks, the researchers collected samples of seawater and aerosols suspended about 20 meters (66 feet) above the ship.
They measured the abundance of what are known as ice-nucleating particles, which seed clouds. They also took stock of seawater chemistry and chlorophyll concentrations, an indicator of phytoplankton abundance.
At first, Creamean said, she simply was hoping to get a baseline sense of the distribution of cloud-seeding particles in the ocean and atmosphere. But on Aug. 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.