Spatial distribution and offshore export of total organic carbon along the eastern boundary of the Subtropical North Pacific

Abstract

Data collected in February, 2003, along the upper continental slope of western North America between Monterey Bay, California (37°N, 122°W), and Cabo San Lucas, Mexico (23°N, 118°W), document, for the first time, the alongshore distribution of total organic carbon (TOC). Highest TOC concentrations (>70 µM) were observed for waters above the nitracline and associated with both California Current and southern surface waters. The northward advection of tropical waters in the California Undercurrent did not have any discernible impact on TOC distributions. An estimate of the average rate at which TOC in surface waters was exported offshore by Ekman transport in February 2003 was 1.73 × 103 kg C yr−1 for each meter of coastline. The offshore flux estimate is thought to be conservative with respect to the annual mean offshore flux because the offshore Ekman transport and primary production increase in late spring and early summer and the contribution of upwelling filaments has not been considered. Analysis of TOC contributions to pelagic respiration suggested that TOC accounted for 45% of the oxygen decrease in southern oxic waters. In California Current and oxygen minimum zone waters, TOC did not contribute to pelagic respiration.