The Inorganic Carbon System and Nutrient Cycling in the Equatorial North Pacific: A study of the interactions between oceanographic features and seawater chemistry

The world’s oceans are an extremely important component of the global carbon cycle. As anthropogenic greenhouse gas emissions become a growing concern, increasing our understanding of the oceanic carbon system will be a key factor in projecting the affects of global climate change and the ability of the oceans to regulate increases in atmospheric CO2. Extensive progress in this area has been made over the past 20 years, but significant gaps still exist. This study examines the carbon system and nutrient cycling processes occurring the north equatorial Pacific along a transect from Kealakekua Bay, Hawaii to Christmas Island, Kiribati. Total dissolved inorganic carbon (DIC) and in situ pCO2 were calculated from the total alkalinity and pH measured at several depths down to 350 meters at eight stations along the transect. It was found that both pCO2 and DIC were regulated by biological and oceanographic factors and that water mass characteristics played an important role in determining parameters of the carbon system. In addition, nutrient data was used to determine which areas along the transect show ratios similar to those projected by the Redfield Ratio. It was found that although slight variations occurred along the transect, the area as a whole demonstrated nutrient ratios which adhered very closely to the Redfield Ratio. While this study provides a baseline for the carbon system parameters in the equatorial north Pacific, further research will be needed to fully define the system and mechanisms taking place in the region.