Flux of particulate inorganic carbon to the deep subarctic Pacific correlates with El Niño

Abstract

Time-series data are presented from sequentially operating deep (3800 m) sediment traps deployed continuously in the northeastern subarctic Pacific between 1982 and 1990. These data show that monthly anomalies in the fluxes of particulate organic carbon (POC) and particulate inorganic carbon (PIC) were significantly correlated with equatorial surface-water temperature anomaly (Niño 3.4 index). This “teleconnection” was stronger for PIC than for POC, and average PIC flux almost doubled from 3.60 to 6.41 mg C m−2 d−1 during the years influenced by El Niño. Average POC flux increased from 2.28 to 3.18 mg C m−1 d−1 during these same years influenced by El Niño, although interpretation of this average was complicated by a single high-flux event in August 1983. Rain ratio (mean daily PIC:POC flux) was ≈25% higher (increased from 1.70 to 2.17) during the years influenced by El Niño. Oceanic sequestration of atmospheric CO2 is particularly sensitive to the rain ratio in the long term, and a decrease in PIC deposition of only 40% has been invoked as sufficient to decrease atmospheric CO2 to the glacial value. An improved mechanistic understanding of the primary formation and sinking of PIC should help to unravel some of the poorly understood biogeochemical feedbacks operating on ocean/atmosphere exchange of CO2 over contemporary and geological time scales.