Biogeochemistry of CO2 system and net community production during mesoscale cyclonic eddies in the lee of Hawaii
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This dissertation characterizes how cyclonic eddy events affect air-sea CO2 exchange and surface water dissolved inorganic carbon (DIC) budget in the lee of Hawaii, an oligotrophic open ocean region in the subtropical North Pacific Gyre. Local steep sea-floor topography and dominant northeasterly trade winds make the lee of main islands of Hawaii an excellent field for eddy study (Seki, et al., 2001; Benitez-Nelson, 2002; Bidigare et al., 2003; Lumpkin, 1998). Three consecutive E-Flux cruises were conducted in November 2004, January 2005 and March 2005, respectively. Discrete water samples were collected with Niskin bottles at individual stations over about 12 discreet depths for pH, Alkalinity and DIC analysis as well as other related biogeochemical parameters. Underway pCO2 measurements were conducted along all transects and at process stations both at the center of an eddy or places affected by eddy (IN) and at places which are outside of eddy (OUTER), providing instant real time information of pCO2 changes in surface water. Based on above measurements, I: 1) discuss the controlling factors of regional CO2 air-sea exchange across cyclonic eddies; 2) estimate regional air-sea CO2 exchange rate by mapping of the difference between surface water pCO2 and atmospheric pCO2 (delata p CO2) and other parameters; 3) estimate the influence of cyclonic eddies on surface water CO2 budget at selected stations in the lee of Hawaii; 4) examine whether cold-core cyclonic eddies can significantly improve net community production (NCP) due to the upwelling of nutrients-rich deep water up to the shallower layer based on the inorganic carbon budget.