Monitoring of a quasi-stationary eddy in the Bay of Biscay by means of satellite, in situ and model results

The presence of a quasi-stationary anticyclonic eddy within the southeastern Bay of Biscay (centred around 44°30′N-4°W) has been reported on various occasions in the bibliography. The analysis made in this study for the period 2003–2010, by using in situ and remote sensing measurements and model results shows that this mesoscale coherent structure is present almost every year from the end of winter-beginning of spring, to the beginning of fall. During this period it remains in an area limited to the east by the Landes Plateau, to the west by Le Danois Bank and Torrelavega canyon and to the northwest by the Jovellanos seamount. All the observations and analysis made in this contribution, suggest that this structure is generated between Capbreton and Torrelavega canyons. Detailed monitoring from in situ and remote sensing data of an anticyclonic quasi-stationary eddy, in 2008, shows the origin of this structure from a warm water current located around 43°42′N-3°30′W in mid-January. This coherent structure is monitored until August around the same area, where it has a marked influence on the Sea Level Anomaly, Sea Surface Temperature and surface Chlorophyll-a concentration. An eddy tracking method, applied to the outputs of a numerical model, shows that the model is able to reproduce this type of eddy, with similar 2D characteristics and lifetimes to that suggested by the observations and previous works. This is the case, for instance, of the simulated MAY04 eddy, which was generated in May 2004 around Torrelavega canyon and remained quasi-stationary in the area for 4 months. The diameter of this eddy ranged from 40 to 60 km, its azimuthal velocity was less than 20 cm s−1, its vertical extension reached 3000–3500 m depth during April and May and it was observed to interact with other coherent structures

Influence of Rossby waves on primary production from a coupled physical-biogeochemical model in the North Atlantic Ocean

Rossby waves appear to have a clear signature on surface chlorophyll concentrations which can be explained by a combination of vertical and horizontal mechanisms. In this study, we investigate the role of the different physical processes in the north Atlantic to explain the surface chlorophyll signatures and the consequences on primary production, using a 3-D coupled physical/biogeochemical model for the year 1998. <br><br> The analysis at 20 given latitudes, mainly located in the subtropical gyre, where Rossby waves are strongly correlated with a surface chlorophyll signature, shows the important contribution of horizontal advection and of vertical advection and diffusion of inorganic dissolved nitrogen. The main control mechanism differs according to the biogeochemical background conditions of the area. <br><br> The surface chlorophyll anomalies, induced by these physical mechanisms, have an impact on primary production. We estimate that Rossby waves induce, locally in space and time, increases (generally associated with the chlorophyll wave crest) and decreases (generally associated with the chlorophyll wave trough) in primary production, ~±20% of the estimated background primary production. This symmetrical situation suggests a net weak effect of Rossby waves on primary production

Coastal and regional marine heatwaves and cold spells in the northeastern Atlantic

The latest Intergovernmental Panel on Climate Change (IPCC) report describes an increase in the number and intensity of marine heatwaves (MHWs) and a decrease in marine cold spells (MCSs) in the global ocean. However, these reported changes are not uniform on a regional to local basis, and it remains unknown if coastal areas follow the open-ocean trends. Surface ocean temperature measurements collected by satellites (from 1982–2022) and 13 coastal buoys (from 1990–2022) are analyzed in the northeastern Atlantic and three subregions: the English Channel, Bay of Brest and Bay of Biscay. The activity metric, combining the number of events, intensity, duration and spatial extent, is used to evaluate the magnitude of these extreme events. The results from in situ and satellite datasets for each of the studied regions are quite in agreement, although the satellite dataset underestimates the amplitude of activity for both MHWs and MCSs. This supports the applicability of the method to both in situ and satellite data, albeit with caution on the amplitude of these events. Also, this localized study in European coastal northeastern Atlantic water highlights that similar changes are being seen in coastal and open oceans regarding extreme events of temperature, with MHWs being more frequent and longer and extending over larger areas, while the opposite is seen for MCSs. These trends can be explained by changes in both the mean of and variance in sea-surface temperature. In addition, the pace of evolution and dynamics of marine extreme events differ among the subregions. Among the three studied subregions, the English Channel is the region experiencing the strongest increase in summer MHW activity over the last 4 decades. Summer MHWs were very active in the English Channel in 2022 due to long events, in the Bay of Biscay in 2018 due to intense events and in the Bay of Brest in 2017 due to a high occurrence of events. Winter MCSs were the largest in 1987 and 1986 due to long and intense events in the English Channel. Finally, our findings suggest that at an interannual timescale, the positive North Atlantic Oscillation favors the generation of strong summer MHWs in the northeastern Atlantic, while low-pressure conditions over northern Europe and a high off the Iberian Peninsula in winter dominate for MCSs. A preliminary analysis of air–sea heat fluxes suggests that, in this region, reduced cloud coverage is a key parameter for the generation of summer MHWs, while strong winds and increased cloud coverage are important for the generation of winter MCSs.</p

National observation infrastructures in a European framework : COAST-HF – an example of a fixed platform network along French coasts

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Taponamiento cardiaco como complicación de terapia trombolítica en paciente con embolia pulmonar masiva

Fundamentos: La embolia pulmonar es una condición frecuente que genera alteraciones en la dinámica cardiovascular y pulmonar. En la actualidad se clasifica de acuerdo a su impacto hemodinámico que permite la instauración de medidas de recuperación de la función cardiaca, la hemodinámica y la pulmonar como la trombólisis. Métodos: Reporte de caso. Resultados: En el presente caso se plantea el de un paciente con embolia pulmonar masiva que presenta una complicación hemorrágica asociada a la trombólisis, el taponamiento cardiaco y fallece. Conclusiones: Las medidas de intervención como la trombólisis para la embolia pulmonar no carecen de complicaciones

Importance of dissolved organic nitrogen in the north Atlantic Ocean in sustaining primary production: a 3-D modelling approach

An eddy-permitting coupled ecosystemcirculation model including dissolved organic matter is used to estimate the dissolved organic nitrogen (DON) supply sustaining primary production in the subtropical north Atlantic Ocean. After an analysis of the coupled model performances compared to the data, a sensitivity study demonstrates the strong impact of parameter values linked to the hydrolysis of particulate organic nitrogen and remineralisation of dissolved organic nitrogen on surface biogeochemical concentrations. The physical transport of dissolved organic nitrogen contributes to maintain the level of primary production in this subtropical gyre. It is dominated by the meridional component. We estimate a meridional net input of 0.039 molNm?2 yr?1 over the domain (13–35 N and 71– 40 W) in the subtropical gyre. This supply is driven by the Ekman transport in the southern part and by non-Ekman transport (meridional current components, eddies, meanders and fronts) in the northern part of the subtropical gyre. At 12 N, our estimate (18 kmolN s?1) confirms the estimation (17.9 kmolN s?1) made by Roussenov et al. (2006) using a simplified biogeochemical model in a large scale model. This DON meridional input is within the range (from 0.05 up to 0.24 molNm?2 yr?1) (McGillicuddy and Robinson, 1997; Oschlies, 2002) of all other possible mechanisms (mesoscale activity, nitrogen fixation, atmospheric deposition) fuelling primary production in the subtropical gyre. The present study confirms that the lateral supply of dissolved organic nitrogen might be important in closing the N budget over the north Atlantic Ocean and quantifies the importance of meridional input of dissolved organic nitrogen

Influence of Rossby waves on primary production from a coupled physical-biogeochemical model in the North Atlantic Ocean

Rossby waves appear to have a clear signature on surface chlorophyll concentrations which can be explained by a combination of vertical and horizontal mechanisms. In this study, we investigate the role of the different physical processes in the north Atlantic to explain the surface chlorophyll signatures and the consequences on primary production, using a 3-D coupled physical/biogeochemical model for the year 1998. The analysis at 20 given latitudes, mainly located in the subtropical gyre, where Rossby waves are strongly correlated with a surface chlorophyll signature, shows the important contribution of horizontal advection and of vertical advection and diffusion of inorganic dissolved nitrogen. The main control mechanism differs according to the biogeochemical background conditions of the area. The surface chlorophyll anomalies, induced by these physical mechanisms, have an impact on primary production. We estimate that Rossby waves induce, locally in space and time, increases (generally associated with the chlorophyll wave crest) and decreases (generally associated with the chlorophyll wave trough) in primary production, ±20% of the estimated background primary production. This symmetrical situation suggests a net weak effect of Rossby waves on primary production

Understanding the influence of Rossby waves on surface chlorophyll concentrations in the North Atlantic Ocean

The variability (in space and time) of westward propagating Rossby waves is analyzed with a wavelet method between 10N and 40N in the North Atlantic Ocean using two remotely sensed data sets (Sea Level Anomalies – SLA and surface chlorophyll-a concentrations) in order to better understand the waves' characteristics and their impacts on the chlorophyll distribution. Signals with wavelengths between ? 500 km and ? 1000 km with ? 4- to ? 24-month periods were detected and identified as the first baroclinic mode of Rossby waves. The spatial and temporal information has also highlighted a particular situation in 1998 at 34N, with the simultaneous existence of two distinct wave components corresponding to wavelengths 500 km and 1000 km.Signatures of the waves in ocean color prompt the question of how Rossby waves influence surface chlorophyll concentrations. Several physical/biological processes have been suggested: the eddy pumping mechanism associated with nutrient injection, the uplifting of a deep chlorophyll maximum toward the surface, and the meridional advection of horizontal chlorophyll gradients by geostrophic currents associated with baroclinic Rossby waves. A statistical decomposition of the observed signal into the different processes modeled by Killworth et al. (2004) confirms a main contribution of the north-south advection of the surface chlorophyll-a gradients south of 28N. In this part of the basin, more than ? 70% of the signal is explained by this horizontal process. North of 28N, Rossby wave signatures seem to be due to the horizontal advection as well as the vertical nutrient injection (? 50% of the observed amplitude). This vertical mechanism may have an impact on the primary production in this part of the basin

Scaling and anisotropic heterogeneities of ocean SST images from satellite data

International audienceOceanic fields display a large variability over large temporal and spatial scales. One way to characterize such variability, borrowed from the field of turbulence, is to consider scaling regimes and multi-scaling properties