Pacific decadal oscillation influences tropical oxygen minimum zone extent and obscures anthropogenic changes.

Abstract

PDO modulates tropical Pacific oxygen content and OMZ volume on decadal time scales.• The PDO-induced variations are of the same order of magnitude as the anthropogenic deoxygenation signal.• Currently available data are too sparse to resolve and isolate the PDO-induced and anthropogenic signals.

The Impact of Fine-Scale Currents on Biogeochemical Cycles in a Changing Ocean

“…There are large, natural variations in marine biogeochemical cycles at interannual to decadal time scales (as shown for instance in air-sea CO2 fluxes by Rodenbeck et al 2015, Landschützer et al 2016, and the scientific consensus is that they are driven by the natural low-frequency variability of the coupled ocean-atmosphere system. This is supported by a large literature where biogeochemical low-frequency variability is related with climate indices such as the El Nino Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), the North Atlantic Oscillation (NOA), the Southern Annular Mode (SAM) or the Pacific Decadal Oscillation (PDO) (Liao et al 2020, Feucher et al 2022, Poupon et al 2023, Lim et al 2022. For example, regarding phytoplankton, ENSO and the IOD have been shown to explain most of phytoplankton variability in the tropical Pacific (Racault et al 2017) and tropical Indian Ocean (Resplandy et al 2009), respectively.…”