We analyse the coupling between sea surface chlorophyll concentration (CC) and the physical environment in the Mozambique Channel (MZC) using statistical models. Seasonal and interannual patterns are studied along with the role of... more
We analyse the coupling between sea surface chlorophyll concentration (CC) and the physical environment in the Mozambique Channel (MZC) using statistical models. Seasonal and interannual patterns are studied along with the role of mesoscale dynamics on enhancement and concentration processes for phytoplankton. We use SeaWifs data for CC and two other remotely sensed data sets, TMMI for sea surface temperature (SST) and merged altimetry products for sea level anomaly and geostrophic current. Empirical Orthogonal Functions (EOF) on SSC and SST show strong seasonality and partition the MZC into three distinct sub-areas. The chlorophyll variability is mostly driven by seasonality, but more in the North (10°S–16°S) and South (24°S–30°S), and explains respectively 64% and 82% of the CC variance. In the Central part (16°S–24°S), the seasonal signal has less influence (60% variance). There, complex EOFs on Sea Level Anomaly (SLA) highlight the role of mesoscale activity (i.e. eddies and fil...
Coastal filaments are generally short-living, non-linear structures that are highly efficient in exporting coastal water and therefore of great relevance to the biogeochemical budget of a basin. Nevertheless, the dynamics governing the... more
Coastal filaments are generally short-living, non-linear structures that are highly efficient in exporting coastal water and therefore of great relevance to the biogeochemical budget of a basin. Nevertheless, the dynamics governing the formation, maintenance and modification of these structures is complex and not completely understood. We present a systematic analysis of the recurrence of filaments after intense rainfall events along
Multi-satellite sea level anomalies from January 1993 to December 2004 are used to investigate the variability of sea surface features in the South China Sea (SCS). Applying empirical orthogonal function (EOF) analysis, the dominant... more
Multi-satellite sea level anomalies from January 1993 to December 2004 are used to investigate the variability of sea surface features in the South China Sea (SCS). Applying empirical orthogonal function (EOF) analysis, the dominant spatial features and ...
The interannual variability in the tropical Indian Ocean, and in particular the Indian Ocean dipole mode (IODM), is investigated using both observations and a multi-decadal simulations performed by the coupled atmosphere–ocean general... more
The interannual variability in the tropical Indian Ocean, and in particular the Indian Ocean dipole mode (IODM), is investigated using both observations and a multi-decadal simulations performed by the coupled atmosphere–ocean general circulation model SINTEX. Overall, the characteristics of the simulated IODM are close to the features of the observed mode. Evidence of significant correlations between sea level pressure anomalies in the southeastern Indian Ocean and sea surface temperature anomalies in the tropical Indian and Pacific Oceans have been found both in observations and a multi-decadal simulation. In particular, a positive SLP anomaly in the southeastern part of the basin seems to produce favorable conditions for the development of an IODM event. The role played by the ocean dynamics both in the developing and closing phases of the IODM events is also investigated. Our results suggest that, during the developing phase, the heat content and SST variability associated with the IODM are influenced by a local response of the ocean to the winds, and a remote response with the excitation of Kelvin and Rossby waves. Ocean wave dynamics appear to be important also during the dying phase of the IODM, when equatorial downwelling Kelvin waves transport positive heat content anomalies from the western to the eastern part of the basin, suppressing the zonal heat content anomaly gradient. The results obtained from the model suggest a mechanism for the IODM. This mechanism is generally consistent with the characteristics of the observed IODM. Furthermore, it might give some clue in understanding the correlation between IODM and ENSO activity found both in the model and in the observations.
The spring and summer distribution of adults and larval fish stages of Sparids and Scorpaenids was studied in two sites in the western Mediterranean. Fish adults and larvae of those two taxa were identified and sorted according to their... more
The spring and summer distribution of adults and larval fish stages of Sparids and Scorpaenids was studied in two sites in the western Mediterranean. Fish adults and larvae of those two taxa were identified and sorted according to their life stages in order to study their distribution and develop suitable habitat maps. Study areas were located on French coastal waters, the “Côte Bleue” Marine Park (CBMP) has an east-west orientation with substratum dominated by Posidonia beds and the Marine Reserve of Cerbe’re-Banyuls (MRCB) runs north-south and is dominated by rocky substrates. Generalised Additive Models (GAM) combined with Geographic Information System (GIS), were used to model the suitable habitats for fish larvae and adults. During spring months, waters exhibit low Sea Surface Temperatures (SST), low Photosynthetically Active Radiation (PAR), high values of Sea Surface Chlorophyll-a concentration (Chl-a), and mostly negative values of Sea Level Anomaly (SLA) indicating anticyclonic eddies. During summer months, waters have higher values of SST, lower values of Chl-a and positive values of SLA indicating cyclonic eddies. The results revealed different environmental responses in the distribution of fish adults and larvae in the CBMP and MRCB. Suitable habitats for adult were mainly dependent on the substrate types (Posidonia meadows and sand) and they were found close to the coast, whereas fish larvae were dependent on environmental cues (Chl-a, SLA, SST) with a sparse spatial distribution.
This paper analyzes the spatial time series of surface chlorophyll (Chl) from the Sea-viewing Wide Field-of-view Sensor and sea level anomaly (SLA) from altimetry satellite data from July 2002 to December 2007 in order to characterize the... more
This paper analyzes the spatial time series of surface chlorophyll (Chl) from the Sea-viewing Wide Field-of-view Sensor and sea level anomaly (SLA) from altimetry satellite data from July 2002 to December 2007 in order to characterize the influence of the regional circulation on the phytoplankton biomass in the Balearic Sea. Correlations between Chl and SLA at seasonal and interannual time
We investigate the tropical Atlantic vertical structure variability (1981–2000) basedon the CLIPPER ocean general circulation model (OGCM). We aim at determining to what extent the observed interannual variability can be explained by the... more
We investigate the tropical Atlantic vertical structure variability (1981–2000) basedon the CLIPPER ocean general circulation model (OGCM). We aim at determining to what extent the observed interannual variability can be explained by the low-frequencywave dynamics. The linear vertical modes of the OGCM climatological stratification are estimated along the equator. The baroclinic mode contributions to surface zonal current and sea level anomalies are calculated and analyzed at interannual time-scales. The second baroclinic mode is the most energetic. The first (third) mode exhibits a variability peak in the west (east). The summed-up contribution of the high-order baroclinic modes (4–6) is as energetic as the gravest modes and is largest in the east. Wave components are then derived by projection onto the associated meridional structures. The effect of longitudinal boundaries near the equator is taken into consideration. Equatorial Kelvin and Rossby waves propagations, with phases speed close to the theory, are identified for the first three baroclinic modes. The comparison with a multimode linear simulation corroborates the propagating properties of the OGCM waves coefficients. An estimationof the meridional boundary reflection efficiency indicates that wave reflections take place at both boundaries. A 65% reflection efficiency is found at the eastern boundary. Our study suggests that low-frequency wave dynamics is to a large extent at work in the tropical Atlantic. On the basis of what is known on the Pacific El Nino-Southern Oscillation mode this may provide a guidance for investigating ocean-atmosphere mechanisms that can lead to the Atlantic zonal equatorial mode.
This work is aimed at studying the variability of Rhodes and Ierapetra Gyres during the Levantine Intermediate Water Experiment. Sea surface temperature maps, derived from Global Area Coverage advanced very high resolution radiometer... more
This work is aimed at studying the variability of Rhodes and Ierapetra Gyres during the Levantine Intermediate Water Experiment. Sea surface temperature maps, derived from Global Area Coverage advanced very high resolution radiometer (AVHRR) data in the framework of the Pathfinder Project and sea level anomalies, derived from TOPEX/Poseidon altimeter, were used to track the evolution, both in terms of dimension and position, of the cyclonic Rhode Gyre and Ierapetra anticyclone. The analysis was performed for the period from October 1994 to the end of April 1995, i.e., from the preconditioning to the spreading phase of Levantine Intermediate Water. The description of the surface fields was complemented by a temporal evolution study of the Rhodes and Ierapetra Gyres hydrological vertical structure. European Centre for Medium-Range Weather Forecasts AVHRR-derived fluxes have been used as forcing for a numerical model to study the variability of the mixed layer in both gyres. The simula...
Evidence is presented demonstrating intermediate water (∼500 m) temperature variability at ODP Hole 893A in Santa Barbara Basin during submillennial climate change (11–60 ka). Benthic δ18O oscillations are considered to result primarily... more
Evidence is presented demonstrating intermediate water (∼500 m) temperature variability at ODP Hole 893A in Santa Barbara Basin during submillennial climate change (11–60 ka). Benthic δ18O oscillations are considered to result primarily from shifts in intermediate water temperature at the site. Detailed comparison of both benthic and planktonic records from the basin provide crucial evidence for differing surface and intermediate water mass temporal responses to rapid climate change. Gradual warming of intermediate water compared to abrupt cooling suggests mechanistic differences between processes controlling North Pacific Intermediate Water expansion and contraction relative to ‘southern component’ intermediate waters. Comparisons suggest intermediate water warming preceded (by 60–200 years) the most rapid interval of surface warming inferred to be associated with North Pacific atmospheric reorganization. Tropical forcing of sea level anomalies in the eastern Pacific via trade wind strength may control California Undercurrent flow (300–500 m) and be the cause of early intermediate water warming in Santa Barbara Basin.