Blowin' in the wind

Natural History, Sept, 2003 by Stephan Reebs

Imagine finding marine plankton drifting through thin air at 30,000 feet. That's the surprise that greeted Kenneth Sassen of the University of Alaska, Fairbanks, and his colleagues when they examined ice crystals collected by a research aircraft that had flown through cirrus clouds over Oklahoma in September 1997. A recent paper by Sassen and his co-authors shows numerous images of variously shaped crystals with cell-like structures embedded in them.

The clouds were remnants of Hurricane Nora, which had originated in the Pacific Ocean, swept up Mexico's Baja Peninsula, and slowed to a tropical storm over the U.S. Southwest. The investigators think Nora's high winds whipped up droplets of seawater and then lofted the droplets, along with their resident plankton, to the top of the troposphere. From there the plankton blew far overland to the east, all the while serving as nucleation points for some of the ice crystals that formed in the clouds. ("Midlatitude cirrus clouds derived from Hurricane Nora: A case study with implications for ice crystal nucleation and shape," Journal of the Atmospheric Sciences 60:873-91, April 1, 2003)

Stephan Reebs is a professor of Biology at the University of Moncton in New Brunswick, Canada, and the author of Fish Behavior in the Aquarium and in the Wild (Cornell University Press).