Trela, Piotr.2014-10-2119961996AAINN16005http://hdl.handle.net/10222/55151Air-sea fluxes of CO$\sb2$ depend on the gas-transfer coefficient (K) and the air-sea difference in the partial pressure of CO$\sb2$ ($\Delta p$). If K and $\Delta p$ covary, the mean air-sea flux of CO$\sb2$ will differ from the flux computed from means of K and $\Delta p$. The difference is termed here the covariance term. Moreover, the partial pressure of CO$\sb2$ in seawater (p) is a nonlinear function of several seawater properties, such as temperature (T), salinity (S), concentration of dissolved inorganic carbon (C) and alkalinity (A). As a result of this nonlinearity, air-sea fluxes computed using mean values of p for a range of seawater conditions will differ from the fluxes calculated using p computed from corresponding means of T, S, C and A. The difference is termed here the carbonate nonlinearity term. Any study of air-sea fluxes of CO$\sb2$, whether based on observations or models, should, ideally, select time and space scales such as to minimize both these terms.In this thesis, I quantify the covariance and the nonlinearity terms at various spatial and temporal scales and explore implications of these results for studies of air-sea fluxes of CO$\sb2$. The spatial component of the nonlinearity term is examined using data collected during the Geochemical Ocean Sections Study (GEOSECS). Standard deviation of p is a good indicator of the magnitude of the nonlinearity term. Failing to consider the spatial fluctuations at the global scale may bias direct estimates of global oceanic uptake of CO$\sb2$ upward by 3.0 GtCy$\sp{-1}$ (=65% of total emissions of anthroprogenic CO$\sb2$ in 1973). Partitioning the global dataset into subsets representing high- and low-latitude waters reduces the bias to 1.4 GtCy$\sp{-1}$.To study the temporal components of the covariance and the nonlinearity terms a new ecosystem model of the Labrador Sea is developed. The model is then used to simulate the annual cycles of K, T, S, C and A. When the annual means of these properties are used to compute air-sea fluxes of CO$\sb2$, both the covariance and the nonlinearity terms are neglected. This results in the overestimation of the air-sea fluxes by 2.4 mol C m$\sp{-2}\rm y\sp{-1}$ (=300% of the estimated total annual uptake of anthropogenic CO$\sb2$ for the Labrador Sea) compared with the best estimate from the ecosystem model. The overstimulation would increase markedly in CO$\sb2$-rich environments. Partitioning the annual cycle into warm and cold seasons reduces the overestimation severalfold.The Labrador Sea model is used to rank the importance of various oceanic processes for air-sea CO$\sb2$ flux. Effects of changes in these processes on the CO$\sb2$ flux would be larger in CO$\sb2$-rich environments.Thesis (Ph.D.)--Dalhousie University (Canada), 1996.Physical Oceanography.Biology, Oceanography.text