HR: 1340h
AN: OS13A-0521    [Abstracts]
TI: Processes Controlling Air-Sea Exchange of CO$_{2}$ in a Subtropical Pacific Estuary
AU: * Fagan, K E
EM: kfagan@hawaii.edu
AF: School of Ocean and Earth Science and Technology, University of Hawaii, 1000 Pope Road, Honolulu, HI 96822 United States
AU: Mackenzie, F T
EM: fredm@iniki.soest.hawaii.edu
AF: School of Ocean and Earth Science and Technology, University of Hawaii, 1000 Pope Road, Honolulu, HI 96822 United States
AU: Andersson, A J
EM: aj@soest.hawaii.edu
AF: School of Ocean and Earth Science and Technology, University of Hawaii, 1000 Pope Road, Honolulu, HI 96822 United States
AB: In contrast to the open ocean, shallow-water coastal ocean air-sea CO$_{2}$ exchange has been given relatively little attention. Available data suggest that continental shelves may act as sinks for atmospheric CO$_{2}$ while estuaries, coral reefs, and upwelling regions, in general may act as sources. However, all data do not comply with these general trends and the data available are geographically relatively scarce and short in duration. Consequently, at the time, it is not possible to unequivocally conclude whether the global shallow-water ocean acts as a source or a sink of atmospheric CO$_{2}$. The present study represents the first evaluation of air-sea CO$_{2}$ exchange for a subtropical high island of the Pacific. Kaneohe Bay, located on the eastern side of Oahu, Hawaii, is a complex estuarine system with a large barrier coral reef, numerous patch reefs, and several riverine inputs. Since Sep 2003 surface water has been collected bimonthly throughout the bay for total alkalinity (TA) and dissolved inorganic carbon (DIC) analysis. The partial pressure of carbon dioxide (P$_{CO2}$) is calculated using TA, DIC, and constants from Mehrbach et al. (1973), refit by Dickson and Millero (1987). For all data collected before Dec 2003, P$_{CO2}$s were above the atmospheric level (375 uatm) for all sites throughout the bay (400 to 1300 uatm). The highest values occurred at sites within Kaneohe Stream. The lowest values, still above atmospheric concentration, occurred at sites outside the barrier reef, indicating that high surface water P$_{CO2}$s extend beyond the boundaries of the bay. Two large storms occurred at the end of Nov 2003 and the end of Feb 2004 that dramatically reduced P$_{CO2}$s to at or below the atmospheric partial pressure throughout the entire bay. This appears to be the result of increased river runoff adding excess nutrients to the bay that enhanced photosynthesis throughout the bay thereby drawing down surface water CO$_{2}$. Despite the significant effects of the storms, average P$_{CO2}$s for Sep 2003 through March 2004 are above the atmospheric level and indicate that Kaneohe Bay probably behaves as a net source of CO$_{2}$ throughout the year because of calcification and perhaps heterotrophy.
DE: 4806 Carbon cycling
DE: 4227 Diurnal, seasonal, and annual cycles
DE: 4235 Estuarine processes
DE: 4504 Air/sea interactions (0312)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting