When we deploy the CTD-Rosette in the open waters of the Arctic Ocean, we often observe a phytoplankton biomass maximum below the surface layer. Our sensors detect this subsurface chlorophyll maximum (SCM) at a depth at which phytoplankton can benefit from nutrients in deeper water layers while still receiving enough sunlight from above for growth. Due to these favorable conditions, SCMs largely contribute to Arctic primary production, which is the accumulation of algal biomass in late spring and summer. While we can easily detect SCMs with our CTD-Rosette to estimate primary production of the Arctic marine ecosystem, SCMs stay largely hidden from ocean color satellites, which are used to estimate phytoplankton production on much larger scales.
Using oceanographic data collected onboard the CCGS Amundsen during the Green Edge campaign in 2016 in Baffin Bay, Lisa Matthes and collaborators investigated the impact of SCMs at different water depths on satellite-based Arctic primary production estimates. Their results show that shallow SCMs above 30 m are partially detected by satellites, which largely decreased the difference between the satellite-based primary production estimate and measured primary production in the region. The findings by Matthes et al. highlight the strength of ocean color applications to complement data collected in field campaigns, and to monitor ongoing changes in the Arctic marine ecosystem.
