Climate effect on food supply to depths greater than 4,000 meters in the northeast Pacific

Abstract

A long time-series study was conducted over 15 yr (1989-2004) to measure particulate organic carbon (POC) flux as an estimate of food supply reaching >4,000-m depth in the northeast Pacific. Sequencing sediment traps were moored at 3,500-and 4,050-m depth, 600 and 50 m above the seafloor, respectively, to collect sinking particulate matter with 10-d resolution. POC fluxes were compared with three climate indices in the Pacific: the basinscale multivariate El Nino Southern Oscillation index (MEI) and northern oscillation index (NOI) and the regionalscale Bakun upwelling index (BUI). The NOI and MEI correlated significantly with POC flux, lagged earlier by 6–10 months, respectively. The BUI also correlated with POC flux, lagged by 2–3 months, suggesting a direct relationship between upwelling intensity and rates of POC supply to abyssal depths. Satellite ocean color data for the surface above the study site were used to estimate chlorophyll a concentrations and, combined with sea surface temperature and photosynthetically available radiation, to estimate net primary production and export flux (EF) from the euphotic zone. EF was significantly correlated with POC flux, lagged earlier by 0–3 months. An empirical model to estimate POC flux, with the use of NOI, BUI, and EF, yielded significant agreement with measured fluxes. Modeling of deep-sea processes on broad spatial and temporal scales with climate indices and satellite sensing now appear feasible.