Oceanography Seminar

September 26, 3:00pm - 4:15pm
Mānoa Campus, Marine Sciences Building 100 Add to Calendar

Barry Huebert
Emeritus Professor
Department of Oceanography

“Requiem for a CLAW
It’s getting hot in here: the thermostat doesn’t work!”

Abstract: In 1987 Charlson, Lovelock, Andrea, and Warren (CLAW) hypothesized a potentially climate-stabilizing feedback loop involving marine phytoplankton physiology, air-sea gas exchange, atmospheric chemistry, aerosol dynamics, cloud physics, and radiative transfer. The algae of interest emit a gas called dimethylsulfide (DMSw), some of which evades to the atmosphere. Some of that DMSa is oxidized to sulfate aerosol (NSS), possibly changing the number of cloud condensation nuclei (CCN) in the process. More CCN produce whiter, more reflective clouds, which permit less solar radiation through to the plankton below them, potentially changing their growth rates and DMS emissions.

It has recently become clear, however, that the CLAW feedback loop itself does not work as hypothesized. Quinn and Bates (2011) showed that DMS does not control CCN concentration in remote marine areas. Our group (Simpson et al. 2013) have shown that DMS is also not the major source of NSS mass near Kiribas, south of Hawaii.

The CLAW Hypothesis stimulated almost 3 decades of work on marine sulfur chemistry above, below, and at the air-sea interface. Perhaps its most important impact is the demonstration that no one discipline can hope to understand the climate system alone. Every project needs to consider interactions and feedbacks with related disciplines and the processes they study. CLAW has been a huge success in that regard.

Although the thermostat doesn’t work, our understanding of marine biogeochemical systems has been forever improved by the publication of the CLAW hypothesis.

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Oceanography, Mānoa Campus

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