Sabine¹, Christopher L., R. A. Feely¹ and Y. Watanabe²

¹NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA, 98115 USA, Tel: 206-526-4809, Fax: 206-526-6744, E-mail: Sabine@pmel.noaa.gov and ²Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, Japan

Temporal evolution of the North Pacific carbon cycle

Time series studies of the North Pacific indicate that CO₂ in near surface waters are increasing at approximately1.3 µmol kg^-1 yr^-1. Subtropical surface waters are estimated to have total concentrations of anthropogenic CO₂ of up to 40-50 µmol kg^-1. The total inventory of anthropogenic CO₂ in the North Pacific is estimated to be ~16.8 Pg C yr^-1 or 37% and 15% of the total Pacific and global inventories, respectively. This relatively low inventory compared to the area of the North Pacific primarily results from the shallow ventilation of mode and intermediate waters. The deep waters of the Pacific are among the oldest in the global oceans and thus have not been exposed to anthropogenic CO₂ contamination. The decrease in carbonate ion concentration resulting from the invasion of anthropogenic CO₂ over the past 150 years has resulted in substantial upward migration of aragonite and calcite saturation horizons in the upper thermocline of the North Pacific. Similarly, several recent studies have suggested the possibly of large-scale changes in thermocline ventilation and/or ecosystem dynamics. The tremendous area, diversity of habitats, and corrosiveness of the Pacific waters with respect to carbonate minerals provide the potential for significant changes in carbon cycling in this ocean as a result of future climate change. Some of these changes may lead to changes in the role of the Pacific as a sink for anthropogenic CO₂. The global CO₂ survey data and estimates provided here make an important baseline for assessing future changes in the Pacific carbon cycle.