Clim. Dynam. http://doi.org/cmfr (2018)

The Humboldt current system — which flows equatorward along the western coast of South America — is a region of strong wind-driven coastal upwelling, the nutrient-rich waters of which fuel extensive biological production. Several studies suggest that Humboldt upwelling will increase in the future due to an intensification of upwelling-favourable winds, but there is contention regarding the robustness of these projections. Damián Oyarzún and Chris Brierley from University College London, UK, investigate future spring-time upwelling in the Humboldt system using a direct estimate of upward ocean mass transport (as opposed to a wind-driven proxy) from 13 coupled general circulation models forced with a strong warming scenario (Representative Concentration Pathway 8.5).

Credit: Kevin Schafer/Alamy Stock Photo

Consistent with previous studies, increased wind stress is found to drive stronger upwelling at the surface (>50 m) by the end of the twenty-first century. Below 100 m, however, a disconnect with wind stress is apparent; coastal upwelling is projected to decline, attributed to enhanced stratification due to warmer ocean temperatures. Such reductions in upwelling could have considerable ecological impacts in one of the most productive ecosystems in the world, and highlight that future projections should consider a synergy of both atmospheric and oceanic factors.