21 January 2015

Ocean Biology Affects Ocean Spray Composition


Oceans cover 70% of the Earth’s surface and clouds that form over the oceans have dramatic effects on Earth’s climate. Every wave that breaks in the ocean produces a stream of bubbles in its wake. When those bubbles reach the ocean surface, they burst creating sea spray. That spray contains salt, but also organic material that is produced by microscopic ocean critters called phytoplankton. Sea spray is an important source of aerosol particles over the ocean, and phytoplankton affect the composition of sea spray aerosol, so phytoplankton can affect the clouds and climate over the ocean. These particles are flung into the air and can affect the formation of cloud droplets. A team of researchers, including DOE scientists from Pacific Northwest National Laboratory, developed a new method to calculate the chemical composition of the sea spray and how it is affected by ocean biology. Until now, climate models have represented sea spray’s chemical composition using equations that describe the observed relationship between the composition of sea spray and the concentration of phytoplankton in the ocean. In this study, for the first time, researchers developed a description of sea spray aerosol chemical composition that is based on a physical model of the processes driving the accumulation of organic matter at the surface of ocean bubbles. The new method will allow researchers to test their understanding of what the most important processes are that determine the composition of sea spray, and may eventually allow researchers to explore how future changes in phytoplankton populations could affect clouds. The new model provides a better description of how phytoplankton affect ocean chemistry and how this, in turn, affects the chemistry of sea spray aerosol. This is important because phytoplankton amounts may change in the future due to warming and acidification of the oceans, and the melting of the polar ice caps. In addition, the new model may help to resolve some apparent discrepancies in the relationships that have been observed between ocean biology and sea spray chemistry in different regions. The model suggests that these relationships may differ between regions depending on the dynamics of the ocean ecosystem.

S M Burrows
Pacific Northwest National Laboratory (PNNL)
Burrows, SM, O Ogunro, AA Frossard, LM Russell, PJ Rasch, and SM Elliott.  2014.  "A Physically Based Framework for Modeling the Organic Fractionation of Sea Spray Aerosol from Bubble Film Langmuir Equilibria."  Atmospheric Chemistry and Physics 14(24): 13601-13629, doi:10.5194/acp-14-13601-2014.