Spatial and temporal variability in nutrients and carbon uptake during 2004 and 2005 in the eastern equatorial Pacific Ocean

The Eastern Equatorial Pacific plays a great role in the global carbon budget due to its enhanced biological productivity linked to the equatorial upwelling. However, as confirmed by the Equatorial Biocomplexity cruises in 2004 and 2005, nutrient upwelling supply varies strongly, also due to the Tropical Instability Waves.

The aim of this study is to examine patterns of spatial and temporal variability in the biological uptake of NO₃, Si(OH)₄ and carbon in this region, and to evaluate the role of biological and physical interactions controlling these processes over seasonal and intra-seasonal time scales.

Here, high resolution Pacific ROMS-CoSiNE model results are combined with in situ and remote sensing data. The results of model-data comparison reveal an excellent agreement in domain-average hydrographic and biological rate estimates, and patterns of spatio-temporal variability in primary productivity.

We demonstrate for the first time that Tropical Instability Waves can be directly linked to increased NO₃ and Si(OH)₄ upwelling supply and enhanced nutrient and carbon uptake, in particular by large phytoplankton such as diatoms. In order to fully resolve the complexity of biological and physical interactions in the Eastern Equatorial Pacific, we recommend improving the CoSiNE model by introducing more phytoplankton groups and a variable Redfield ratio.