A four‐dimensional mesoscale map of the spring bloom in the northeast Atlantic (POMME experiment): Results of a prognostic model

Abstract

[1] A prognostic high-resolution model is established to provide an integrated view of the evolution of the spring bloom during the Programme Océan Multidisciplinaire Méso Echelle (POMME) experiments carried out at sea from February to May 2001 (16-22°W and 38°-45°N). Data collected during the first survey were used for model initialization, and data from three other cruises were used for model validation. The model successfully predicts the time evolution of the main reservoirs and fluxes, except for a storm event during postbloom conditions, for which the biological impact is underestimated. The bloom is long in duration (2 months), has low intensity (1 mg Chl m À3 ), and is characterized by a small f-ratio (0.45) and a small e-ratio (0.05). Furthermore, the model reveals much stronger space and time variability than sampled in the data. This large variability results both from the synoptic atmospheric variability and from the stirring induced by oceanic mesoscale eddies. In particular, the bloom starts in specific submesoscale features that correspond to filaments of minimum mixed layer depth. On short timescales (2-3 days), space and time variability have the same order of magnitude. On the seasonal timescale, time variability is larger than space variability. Considering the transient state of the system, this modeling exercise is also used to quantify the nonsynopticity of the observations, which occur mostly during bloom conditions, a crucial point for the data interpretation.

Vertical distribution of aggregates (>110 µm) and mesoscale activity in the northeastern Atlantic: Effects on the deep vertical export of surface carbon

“…Once the aggregates were concentrated in these areas, they would settle out or could be entrained into the ageostrophic vertical circulation that takes place at subscale to mesoscale levels. Upward and downward velocities are generally high in the mesopelagic layer at eddy boundaries (a few tens of m d 21 ; Pollard and Regier 1990;Allen et al 2001;Levy et al 2005). Combined settling of aggregates and maximum downward convective transport can enhance the total vertical speed (up to more than 100 m d 21 ), which could explain the export of aggregates to 1,000 m in less than 10 d.…”

Influence of numerical schemes on current-topography interactions in 1/4° global ocean simulations

“…The consequences of the spurious "no-slip-like" sidewall friction hypothesized in CLIPPER at 1/6 • were much less visible at low latitudes, where local Rossby radii were properly resolved . The OFES global model (Masumoto et al, 2004) is based on MOM, uses partial steps with a no-slip sidewall friction like OCCAM, but simulates a reasonable Zapiola Anticyclone at 1/10 • resolution. Both facts suggest that increased resolution reduces the adverse effects of no-slip conditions, either introduced explicitly (e.g.…”

“…Along with the ongoing (and beneficial) increase of basin-and global-scale ocean model resolution (Paiva et al, 1999;Smith et al, 2000;Eden and Böning, 2002;Masumoto et al, 2004;Chanut et al, 2007), eddyadmitting ocean models require further investigation since the 1 4…”

Stochastic estimation of biogeochemical parameters from Globcolour ocean colour satellite data in a North Atlantic 3D ocean coupled physical–biogeochemical model

“…The vertical coordinate is geopotential with 46 prescribed levels enabling a resolution from 6 to 15 meters in the upper 100 meters. The physical model computes the advection and diffusion terms of the biogeochemical variables included in the model LOBSTER model (Lévy et al (2005)). …”

“…In Ourmières et al (2009), the parameterization of the biogeochemical model was tuned in the NATL4 configuration as described in Lévy et al (2005), and the model was further validated using uniform values for the triplet µ (0.60 day −1 ), m (0.05 day −1 ) and g (0.80 day −1 ).…”