The goal of this project is to understand the control that biological productivity exerts on the rate of atmospheric CO2 uptake and how this productivity is related to the phytoplankton abundance and community structure of the ecosystem. This is to be be accomplished by quantifying the rates of air-sea CO2 flux, biological productivity rates and phytoplankton composition across the subarctic and subtropical N. Pacific ocean. It is anticipated that the results will provide a much-needed data set to validate ocean carbon cycle model simulations of CO2 uptake and improve predictions of the response of ocean�??s CO2 uptake to global warming. The approach utilizes ship-board analytical techniques (continuous flow mass spectrometry, flow cytometry and sensors) to obtain underway measurements of temperature, salinity, dissolved gases (CO2, O2 and Ar), phytoplankton composition, chlorophyll a and nitrate concentrations. A container ship that crosses the subtropical and subarctic gyres and intervening biologically productive frontal region that experiences very high oceanic CO2 uptake rates will be used as the underway sampling platform to obtain repeated measurements along a cruise track between Hong Kong and Long Beach, CA . The seasonal and spatial (at ~ 1km resolution) variability of the air-sea CO2 flux, net community production rate and ecosystem characteristics (phytoplankton composition, chlorophyll a and nitrate levels) across the N Pacific basin will be determined. These data will be the basis for quantifying the impact that biological productivity (and SST) has on the air-sea CO2 flux and how biological productivity is related to ecosystem community structure.