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Biogeochemistry of Co2 System and Net Community BIOGEOCHEMISTRY OF CO2 SYSTEM AND NET COMMUNITY PRODUCTION DURING MESOSCALE CYCLONIC EDDIES IN THE LEE OF HAWAII by FEIZHOU CHEN (Under the Direction of Wei-Jun Cai) ABSTRACT 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 (ΔpCO2) 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. INDEX WORDS: Mesoscale processes, Cyclonic eddies, Dissolved inorganic carbon (DIC), Net community production (NCP), Carbon cycle, CO2, CO2 fluxes, Global warming, the lee of main Hawaiian Islands, Subtropical North Pacific Ocean, E-Flux BIOGEOCHEMISTRY OF CO2 SYSTEM AND NET COMMUNITY PRODUCTION DURING MESOSCALE CYCLONIC EDDIES IN THE LEE OF HAWAII by FEIZHOU CHEN B.S., Xiamen University, P. R. China, 1992 PhD, Xiamen University, P. R. China, 1997 A Dissertation Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY ATHENS, GEORGIA 2008 © 2008 FEIZHOU CHEN All Rights Reserved BIOGEOCHEMISTRY OF CO2 SYSTEM AND NET COMMUNITY PRODUCTION DURING MESOSCALE CYCLONIC EDDIES IN THE LEE OF HAWAII by FEIZHOU CHEN Major Professor: Wei-Jun Cai Committee: Claudia R. Benitez-Nelson Richard A. Jahnke Ming-Yi Sun Chuanlun Zhang Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia May 2008 ACKNOWLEDGEMENTS First of all, I want to thank my major advisor, Dr. Wei-Jun Cai for his continuous instruction and great help all these years. I want to thank all my committee members, who have made valuable suggestions to this work. Special thanks to Dr. Benitez-Nelson for inviting us to the E-Flux cruises and her great help in editing my publications related to this dissertation. I wish to thank all E-Flux collaborators, especially Dr. R. Bidigare and Yoshimi Rii for providing nutrients, TOC, and DON data for this dissertation. Many thanks to Dr. T. Dickey, W. Black, F. Nencioli, Dr. V. Kuwahara, Dr. K. Maiti, P. McAndrew, J. Becker, Dr. T. Bibby, and Dr. Michael Landry’s group for their great help for me to access the shipboard data and sampling collection. I am grateful to C. L. Leonard and the NOAA Ocean Watch Central Pacific for the satellite SST image. Thank the crews of R/V Ka’imikai-O-Kanaloa (KOK) and R/V Wecoma for providing supports for our sampling cruises. Gratitude to all the colleagues in my lab for their great help all these years, especially, Dr. Yongchen Wang and Ms. Guirong Han for their laboratory support for sample analysis and for their mental support. I would also like to thank Li-Qing Jiang, Justin Hartmann, Dr. Xinping Hu, and Wei-Jen Huang for their great help all these years. I am grateful to all the friends and colleagues in our department, especially Dr. James Hollibaugh, Dr. Mary Ann Moran, Cedric Fichot, Dr. Sarah Cooley, Paul McKay, Dr. Daniela Di Iorio, Dr. Charles Tilburg, Erin Biers, and Weidong Zhao for their diverse help to my dissertation. iv TABLE OF CONTENTS Page ACKNOWLEDGEMENTS........................................................................................................... iv LIST OF TABLES........................................................................................................................ vii LIST OF FIGURES ....................................................................................................................... ix CHAPTER 1 Introduction....................................................................................................................1 2 Site description & research methods..............................................................................7 Description of three E-Flux cruises and sampling strategy.......................................8 Brief introduction to the phases of life cycle for Cyclones Opal and Noah............13 Sample collection and analysis................................................................................15 3 Sea surface pCO2-SST relationships across cold-core cyclonic eddies: Implications for understanding regional variability and air-sea gas exchange ............................32 Introduction .............................................................................................................33 Section 3.1 Cyclone Opal.......................................................................................35 Section 3.2 Cyclone Noah......................................................................................48 Section 3.3 Seasonal variation of CO2 air-sea exchange across cyclonic eddies in the lee of Hawaii................................................................................................53 4 The carbon dioxide system and net community production during mesoscale cyclonic eddies.......................................................................................................................74 Introduction .............................................................................................................75 Section 4.1 Inorganic carbon dynamics in the lee of main Hawaiian Islands........78 v Section 4.2 Descriptions of mass balance models fro NCP estimation..................88 Section 4.3 NCP in Cyclone Opal..........................................................................96 Section 4.4 NCP in Cyclone Noah .......................................................................107 Section 4.5 Conclusions and significance ............................................................114 5 Summary....................................................................................................................146 REFERENCES ............................................................................................................................151 vi LIST OF TABLES Page Table 2.1: Stations and casts information for E-Flux I cruise .......................................................20 Table 2.2: Stations and casts information for E-Flux II cruise......................................................21 Table 2.3: Stations and casts information for E-Flux III cruise.....................................................22 Table 3.1: Calculated sea surface pCO2 of different water masses for Cyclone Opal...................58 Table 3.2: Sea-to-air CO2 fluxes in the lee of Hawaii during E-Flux III eddy cruise ...................59 Table 3.3: Calculated sea surface pCO2 of different water masses for Cyclone Noah..................60 Table 3.4: Sea-to-air CO2 fluxes in the lee of Hawaii during E-Flux I eddy cruise ......................61 Table 3.5: Sea-to-air CO2 fluxes in the lee of Hawaii during E-Flux II eddy cruise.....................62 Table 3.6: Average sea surface pCO2 and SST during E-Flux I-III cruises ..................................63 Table 4.1: Average observed depth-integrated temperature and salinity in E-Flux III and II.....119 Table 4.2: Average observed concentrations at OUT-stations in E-Flux II and III.....................120 Table 4.3: Average observed depth-integrated temperature and salinity in E-Flux I..................121 Table 4.4: Selected average observed concentrations at OUT-stations in E-Flux I-III...............122 Table 4.5: OUT-stations NCP and other net carbon flux terms in E-Flux III .............................123 Table 4.6: Average observed and expected concentrations at IN-stations in E-Flux III .............124 Table 4.7: IN-stations NCP from two end-member mixing model in E-Flux III ........................125 Table 4.8: OUT-stations NCP and other net carbon flux terms in E-Flux I ................................127 Table 4.9: Observed and expected concentrations at individual IN-stations in E-Flux I ............128 Table 4.10: IN-stations NCP estimates during E-Flux I..............................................................129 vii Table 4.11: The corrected IN-station NCP estimates after considering the net effect of evaporation/precipitation during E-Flux I...................................................................130 viii LIST OF FIGURES Page Figure 1.1: Climatological mean seasonal distribution
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