Subtropical Gyre Nutrient Cycling in the Upper Ocean: Insights From a Nutrient‐Ratio Budget Method

Abstract

Abstract We use a nutrient‐ratio budget method to investigate the relative importance of different nutrient source and sink terms at time‐series Station ALOHA and Bermuda Atlantic Time‐series Study (BATS) in the North Pacific and North Atlantic subtropical gyres, respectively. At mean state conditions over annual and multi‐year time scales, vertical phosphate (PO43–) supply from the subsurface accounts for ∼60% of the total phosphorus supply at both sites. Dissolved organic matter transport and zooplankton excretion are more important phosphorous export pathways than sinking particles at Station ALOHA and BATS. The nutrient‐ratio budget approach provides quantitative, observation‐based constraints on nutrient sources and sinks in the surface ocean, which helps improve our understanding of the biological carbon pump in oligotrophic oceans.

Keywords

• nutrient budgets
• elemental stoichiometry
• biological pump
• subtropical gyre
• dissolved organic matter
• zooplankton excretion