Linking Phytoplankton Variability to Atmospheric Blocking in an Eastern Boundary Upwelling System

The oceanic ecosystems in the eastern boundary upwelling systems (EBUS) are expected to be influenced by climate change, but specific mechanisms describing their connections are not well understood. Using a 20-year time-series record of satellite and climate data, we identified a strong linkage between phytoplankton variability in a EBUS and a high latitude, large-scale atmospheric process. The winter-spring phytoplankton variability in the Canary Current Upwelling System was associated to the atmospheric blocking events over Greenland. These Greenland blocking events were primarily caused by the persistence of quasi-stationary, large-scale high atmosphere pressure fields. These fields forced the eddy-driven jet stream to shift south, which caused a weakening of the equatorward alongshore winds over the upwelling system. As a result, the wind-driven upwelling was suppressed, and phytoplankton growth was inhibited. These results identified a previously unknown source driving interannual phytoplankton variability in the EBUS, underscoring the importance of contributions of atmospheric connections on the coastal upwelling ecosystems.

Automated summary

Using a 20-year time-series record, this study identified a strong linkage between phytoplankton variability in the eastern boundary upwelling systems (EBUS) and a high latitude, large-scale atmospheric process. Blocking events over Greenland caused a weakening of wind-driven upwelling, leading to inhibited phytoplankton growth. These findings underscore the importance of atmospheric connections in coastal upwelling ecosystems.