Biological Revelance of Submesoscale Processes in the Stratified, Oligotrophic Ocean

Submesoscale processes have been shown to be important in regions of low stratification and deep mixed layers. We investigate the importance of submesoscale nutrient injections in a region of the North Pacific ocean with shallow mixed layers and high stratification. A simple, nitrogen-based plankton model is embedded in a ROMS configuration for the Hawaiian region centered on Station ALOHA (part of the Hawaii Ocean Time-series, HOT). As the grid resolution is increased, shoaling of the average depth of the nutricline and frequency of episodic nitrate injections are increased due to the larger vertical velocity variance and larger buoyancy variance just below the mixed layer. As a consequence, large phytoplankton species, absent at lower resolutions, emerge. The modeled primary productivity at Station ALOHA is enhanced during these episodic injection events. These results are important in the context of the observed primary productivity patterns. In regions with low surface NO3:PO4 ratios, episodic injections supply an excess of PO4 relative to Redfield stoichiometry. Phosphate is a limiting nutrient for nitrogen-fixing diazotroph growth at Station ALOHA, which may help explain the observed primary productivity pattern.

Paulo H. R. Calil - Universidade Federal do Rio Grande (FURG)
Yawei Luo - Woods Hole Oceanographic Institution (WHOI)
Ivan Lima - Woods Hole Oceanographic Institution (WHOI)
Scott C. Doney - Woods Hole Oceanographic Institution (WHOI)