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2671751 
Journal Article 
The viscosity effect on marine particle flux: A climate relevant feedback mechanism 
Taucher, J; Bach, LT; Riebesell, U; Oschlies, A 
2014 
Yes 
Global Biogeochemical Cycles
ISSN: 0886-6236
EISSN: 1944-9224 
28 
4 
415-422 
WOS:000335809500006 
Oceanic uptake and long-term storage of atmospheric carbon dioxide (CO2) are strongly driven by the marine biological pump, i.e., sinking of biotically fixed inorganic carbon and nutrients from the surface into the deep ocean (Sarmiento and Bender, ; Volk and Hoffert, ). Sinking velocity of marine particles depends on seawater viscosity, which is strongly controlled by temperature (Sharqawy et al., ). Consequently, marine particle flux is accelerated as ocean temperatures increase under global warming (Bach et al., ). Here we show that this previously overlooked viscosity effect could have profound impacts on marine biogeochemical cycling and carbon uptake over the next centuries to millennia. In our global warming simulation, the viscosity effect accelerates particle sinking by up to 25%, thereby effectively reducing the portion of organic matter that is respired in the surface ocean. Accordingly, the biological carbon pump's efficiency increases, enhancing the sequestration of atmospheric CO2 into the ocean. This effect becomes particularly important on longer time scales when warming reaches the ocean interior. At the end of our simulation (4000A.D.), oceanic carbon uptake is 17% higher, atmospheric CO2 concentration is 180ppm lower, and the increase in global average surface temperature is 8% weaker when considering the viscosity effect. Consequently, the viscosity effect could act as a long-term negative feedback mechanism in the global climate system.



Key Points



<list list-type="bulleted" id="gbc20151-list-0001"> <list-item id="gbc20151-li-0001">Global warming reduces seawater viscosity, thus accelerating particle sinking <list-item id="gbc20151-li-0002">Faster sinking enhances the biological pump and oceanic carbon uptake <list-item id="gbc20151-li-0003">This viscosity effect is a previously overlooked climate feedback mechanism 
biogeochemistry; climate change; marine carbon cycle; particle sinking