Nuno Cordeiro

Towards Operational Modeling and Forecasting of the Iberian Shelves Ecosystem

There is a growing interest on physical and biogeochemical oceanic hindcasts and forecasts from a wide range of users and businesses. In this contribution we present an operational biogeochemical forecast system for the Portuguese and Galician oceanographic regions, where atmospheric, hydrodynamic and biogeochemical variables are integrated. The ocean model ROMS, with a horizontal resolution of 3 km, is forced by the atmospheric model WRF and includes a Nutrients-Phytoplankton-Zooplankton-Detritus biogeochemical module (NPZD). In addition to oceanographic variables, the system predicts the concentration of nitrate, phytoplankton, zooplankton and detritus (mmol N m−3). Model results are compared against radar currents and remote sensed SST and chlorophyll. Quantitative skill assessment during a summer upwelling period shows that our modelling system adequately represents the surface circulation over the shelf including the observed spatial variability and trends of temperature and chlorophyll concentration. Additionally, the skill assessment also shows some deficiencies like the overestimation of upwelling circulation and consequently, of the duration and intensity of the phytoplankton blooms. These and other departures from the observations are discussed, their origins identified and future improvements suggested. The forecast system is the first of its kind in the region and provides free online distribution of model input and output, as well as comparisons of model results with satellite imagery for qualitative operational assessment of model skill.

Numerical modelling of the phytoplankton patterns in an upwelling event off the NW Iberian Margin

ABSTRACT Rocha, C., Cordeiro, N., Nolasco R., Dubert J., 2013. Numerical modelling of the phytoplankton patterns in an upwelling event off the NW Iberian Margin. An extreme event in September 2007, presenting a strong upwelling core detaching from the Galician NW coast and extending towards west-northwest from the Cape Finisterre - Cape Ortegal zone, with the formation of several filaments and a consequent strong response in chlorophyll concentration values is analyzed. To do so, a NPZD biogeochemical module coupled to a ROMS_Agrif configuration is used. The model response was satisfactory and an analysis of the event, including its forcing, was made. The particular wind direction and intensity along with the specific coastal orientation of the study area were identified as important characteristics for the development of the event. The analysis of the behavior and evolution of this phytoplankton bloom may give further insight in the relations between atmospheric forcing, the consequent characteristic coastal ocean processes, and their conditioning in phytoplankton distribution and patterns in the study area.

Filaments on the Western Iberian Margin: A modeling study

Coastal upwelling filaments off the Western Iberian Margin, detected in AVHRR satellite imagery and in a realistic ROMS simulation of sea surface temperature, were studied in the upwelling seasons (May–October) of 2001–2010. Sea surface temperature data were retrieved from AVHRR satellite imagery and from a realistic ROMS numerical simulation. The development and variability of the observed filaments were characterized and analyzed during each upwelling season of the 10 year period. Filaments were generally found anchored to the main bathymetric and coastal features but off the more regular northern coast of the Western Iberian Margin their locations were more variable. The results from the modeling analysis reproduced well the general features of filament development. Moreover results of model and observation showed very similar characteristics as those found in the earlier study of Haynes et al. (1993). The model output was used to relate filament patterns, eddy activity, and wind forcing. There was a clear relation between upwelling-favorable wind strength and number and length of filaments, although the relation was weaker in the north of the region. Model filaments were clearly related to eddies only during periods of weak winds. The filament detection method was also applied to a climatologically forced ROMS simulation, which reproduced only gross features of the observed and interannually forced model filament development. This suggests that direct wind forcing and its spatial structure are highly important.

Transient response of the Northwestern Iberian upwelling regime

The hydrography and dynamics of NW Iberian margin were explored for July 2009, based on a set of in situ and remote sensing observations. Zonal sections of standard CTD casts, towed CTD (SeaSoar), Acoustic Doppler Current Profilers (ADCP) and Lagrangian surveys were made to characterize cycles of upwelling and relaxation in this region. Two periods of northerly winds, bounded by relaxation periods, were responsible for the formation of an upwelling front extending to the shelf edge. An equatorward flow was quickly set up on the shelf responding to the northerly wind pulses. South of Cape Silleiro, the development and subsequent relaxation of an upwelling event was intensively surveyed in the shelf, following a Lagrangian drifter transported by the upwelling jet. This region is part of an upwelling center extending from Cape Silleiro to Porto, where the surface temperature was colder than the neighboring regions, under upwelling favorable winds. As these winds relaxed, persistent poleward flow developed, originating south of the upwelling center and consisting in an inner-shelf tongue of warm waters. During an event of strong southerly wind, the poleward flow was observed to extend to the whole continental shelf. Although the cruise was executed during summertime, the presence of river-plumes was observed over the shelf. The interaction of the plumes with the circulation on the shelf was also described in terms of coastal convergence and offshore advection. The sampling of the offshore and slope regions showed the presence of the Iberian poleward current offshore and a persistent equatorward flow over the upper slope.

Correction: Transient response of the Northwestern Iberian upwelling regime

[This corrects the article DOI: 10.1371/journal.pone.0197627.].