Abstract
We validated simulations of the Earth system model (ESM) EC-Earth-NEMO of present-day temperature, salinity, nutrient, and chlorophyll a profiles with in situ observations in the Northeast Atlantic Ocean (29–63º N). Simulations with standard parametrization (run 1) and improved parametrization of vertical mixing (run 2) were compared. Run 1 showed shallower mixed layer depths (MLDs) in spring as compared to observations owing to lower salinities in the upper 200 m of the subpolar North Atlantic (>55º N). This coincided with a mismatch with observed timing and magnitude of the phytoplankton spring bloom. In contrast, the model performed well south of 55º N. Run 2 showed improved springtime MLD, phytoplankton dynamics, and nutrient distributions in the subpolar North Atlantic. Our study underlines the sensitivity of subpolar North Atlantic phytoplankton blooms to surface freshening, suggesting that future fresh-water inflow from Arctic and Greenland Ice sheet melting could significantly affect phytoplankton productivity. These findings contribute to the generic validation of the EC-Earth ESM and underline the need for rigorous validation of physics-biology links, in particular the sub polar North Atlantic where complex seasonal stratification/vertical mixing processes govern upper ocean phytoplankton productivity.
Highlights
The oceans play a critical role in the global carbon cycle since they harbor enormous pools of inorganic as well as organic carbon [1]
Geosciences 2019, 9, 450 composition influence marine productivity up to the highest trophic levels, including harvestable stocks, studying the climate processes and interactions that control phytoplankton dynamics is of vital importance in predicting the future of marine ecosystems under a changing climate
Model run 1 showed lower than observed salinity in the upper 200 m, which wasand most phytoplankton Chlorophyll a (Chl a)
Summary
The oceans play a critical role in the global carbon cycle since they harbor enormous pools of inorganic as well as organic carbon [1]. Phytoplankton biomass, expressed as chlorophyll-a concentrations, varies strongly on interannual and decadal timescales [3,4]. This variability correlates with climatic variations that regulate the availability of irradiance, nutrients, viral lysis, grazers, and the sinking speed of the cells [5,6,7,8]. Vertical mixing and stratification are important mechanisms controlling phytoplankton growth, since these determine to a large extent the availability of light and nutrients [6,9]. The shoaling of the mixed layer (ML), owing to salinity or temperature stratification, confines phytoplankton close to the surface where it is exposed to increased irradiance and nutrients.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
