Data assimilation of depth-distributed satellite chlorophyll-α in two Mediterranean contrasting sites

Abstract

A new approach for processing the remote sensing chlorophyll-α (Chl-α) before assimilating into an ecosystem model is applied in two contrasting, regarding productivity and nutrients availability, Mediterranean sites: the DYFAMED and POSEIDON E1-M3A fixed point open ocean observatories. The new approach derives optically weighted depth-distributed Chl-α profiles from satellite data based on the model simulated Chl-α vertical distribution and light attenuation coefficient. We use the 1D version of the operational ecological 3D POSEIDON model, based on the European Regional Seas Ecosystem Model (ERSEM). The required hydrodynamic properties are obtained (off-line) from the POSEIDON operational 3D hydrodynamic Mediterranean basin scale model. The data assimilation scheme is the Singular Evolutive Interpolated Kalman (SEIK) filter, the ensemble variant of the Singular Evolutive Extended Kalman (SEEK) filter. The performance of the proposed assimilation approach was evaluated against the Chl-α satellite data and the seasonal averages of available in-situ data for nitrate, phosphate and Chl-α. An improvement of the model simulated near-surface and subsurface maximum Chl-α concentrations is obtained, especially at the DYFAMED site. Model nitrate is improved with assimilation, particularly with the new approach assimilating depthdistributed Chl-α, while model phosphate is slightly worse after assimilation. Additional sensitivity experiments were performed, showing a better performance of the new approach under different scenarios of model Chl-α deviation from pseudo-observations of surface Chl-α.

Home range and foraging habitat preference of Scopoli's shearwater Calonectris diomedea during the early chick‐rearing phase in the eastern Mediterranean

“…Contrary to expectations, the main foraging areas in the Ionian Sea during the early chick-rearing phase are not particularly productive and are characterized as lower mesotrophic to oligotrophic (Fig. 5a), with CHL levels of less than 0.10 mg m -3 (Kalaroni et al 2016). These results are in accordance with Cecere et al (2013) who showed that, during chick-rearing, Scopoli's shearwater breeders forage in less profitable areas, closer to their colonies in the central Mediterranean Sea.…”

An integrated open-coastal biogeochemistry, ecosystem and biodiversity observatory of the eastern Mediterranean – the Cretan Sea component of the POSEIDON system

“…mesocosms; see Sect. 4.8) for the analysis and modelling of specific processes, such as the microbial functioning and the effect of the atmospheric deposition (Christodoulaki et al, 2013;Tsiaras et al, 2017), or for the assimilation algorithms of sea colour data in BGC models (Kalaroni et al, 2016).…”

Ecoregions in the Mediterranean Sea Through the Reanalysis of Phytoplankton Functional Types and Carbon Fluxes

“…This system uses the coupled physical-biogeochemical model Proudman Oceanographic Laboratory Coastal Ocean Modelling System (POLCOMS)-European Regional Seas Ecosystem Model (ERSEM) of the Mediterranean Sea developed by Holt et al (2008) and updated by Kay and Butenschön (2018), and we applied the PFT assimilation framework developed by Ciavatta et al (2018). Previous applications of ERSEM to investigate the Mediterranean Sea biogeochemistry, in both assimilative and not assimilative simulations, include the works by Vichi et al (1998), Allen et al (1998Allen et al ( , 2002Allen et al ( , 2003, Petihakis et al (1999Petihakis et al ( , 2002Petihakis et al ( , 2007, Triantafyllou et al (2000Triantafyllou et al ( , 2003, Zavatarelli et al (2000), Blackford (2002), Pinardi et al (2003), Kalaroni et al (2016), and Tsiaras et al (2017). A skill assessment was performed to evaluate the reanalysis adequacy in representing the average spatial variability of the phytoplankton community structure.…”