Nature Climate Change, Published online: 02 September 2025; doi:10.1038/s41558-025-02380-4
The ocean carbon sink strengthened in previous warm El Niño years due to reduced CO2 outgassing in the tropics. Here the authors show that the ocean carbon sink declined in 2023 despite record-high sea surface temperatures (SSTs), primarily due to SST-driven outgassing of CO2 in the subtropics.