Control factors of DIC in the Y3 seamount waters of the Western Pacific Ocean

Abstract

An investigation was carried out in the Y3 seamount area of the Western Pacific Ocean in December 2014, and the distribution of dissolved inorganic carbon (DIC) and its relationship with environmental factors in this area were explored. The results show that DIC concentration was higher in the adjacent waters of the Y3 seamount area, and the uplift of DIC isolines at the stations was close to the seamount. Meanwhile, interaction between the North Equatorial Current (NEC) and the Y3 seamount aff ected the DIC distribution, i.e., the upwelling in the same direction of the NEC was obvious, resulting in a decreasing trend of average concentration of DIC in the 200 m water column from the top to the two sides in this direction but in the cross direction. The DIC concentration increased with the water depth increase, and its distribution was aff ected by various environmental factors. In the surface water, high temperature was a decisive factor for the decrease of the DIC concentration, but the photosynthesis of phytoplankton showing only a weak influence. In the North Pacific Tropic Water (NPTW), DIC production rate from organic matter decomposition was higher than that of DIC consumption by phytoplankton photosynthesis, leading to a continual increase of DIC. In the North Pacific Intermediate Water (NPIW), organic matter decomposition played a leading role in the increase of DIC. In the deep water, decomposition of organic matter weakened, and the dissolution of CaCO3 controlled the carbonate system, and DIC had the smallest variation range.