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Introduction
Guillaume Charria currently works at the Laboratory of Ocean Physics and remote Sensing (LOPS), Institut Français de Recherche pour l'Exploitation de la Mer. Guillaume does research in Oceanography.
Additional affiliations
June 2009 - January 2016
Publications
Publications (54)
Decadal time series of chlorophyll-a concentrations sampled at high and low frequencies are explored to study climate-induced changes on the processes inducing interannual variations in the Initiation of the Phytoplankton Growing Period (IPGP) in early spring. In this study, we specifically detail the IPGP in two contrasting French coastal ecosyste...
In this paper, the problem of vertical shear flow instabilities at the base of a river plume and their consequences in terms of turbulent energy production and mixing is addressed. This study was carried out using 2D non-hydrostatic simulations and linear stability analysis. The initial conditions used in these simulations were similar to those obs...
Extreme weather events affect coastal marine ecosystems. The increase in intensity and occurrence of such events drive modifications in coastal hydrology and hydrodynamics. Here, focusing on the winter period (from December to March), we investigated multi-decade (2000–2018) changes in the hydrological properties of the Bay of Brest (French Atlanti...
Journal website link: www.frontiersin.org I n r e v i e w Conflict of interest statement The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest Author contribution statement AA, GC and XC designed the study. AA, GC, XC and NA contrib...
The regional and coastal ocean, as a complex interface area where land, hydrology, atmosphere, and ocean interact, concentrates a wide range of actors dealing with increasing socioeconomic and environmental issues. Under the pressure of the impacts of climate change, forecasting the coastal ocean remains a key challenge.
The International Coastal...
Poster présenté aux Secondes Journées du GDR Polymères & Océans
https://www.po2020.fr/
In the Bay of Biscay (north-east Atlantic), long-living eddies and the frontal activity that they induce substantially contribute to mesoscale and submesoscale dynamics. Tides and river plumes also contribute to frontal activity. Biological productivity is sensitive to river plume fronts and to external forcings (tides and wind). Considering the im...
Coastal marine ecosystems worldwide are not only highly affected by the effects of human activities, but also by the influence of natural climate variability and global climate change. However, it is still a challenge to assess the spatial and temporal scales at which forcings operate and their persistence over time, to determine the vulnerability...
The spatio-temporal distribution of cross-shelf exchanges in the northern Bay of Biscay from 2007 to 2010 were investigated using a high-resolution three-dimensional model as well as sea-surface temperature and chlorophyll-a concentration satellite observations. Our results show that the net yearly mean transport was upslope each year, with 2010 sh...
We discuss paleoenvironments of north-western France over the last 7 kyrs in terms of: i) long-term changes (relative sea-level rise and boreal summer insolation), ii) rapid climate changes (millennial-scale Bond events and multi-decadal regimes of the North Atlantic Oscillation: NAO) and iii) growing human impacts in watersheds. Our study focuses...
The coastal area is the most productive and dynamic environment of the world ocean, offering significant resources and services for mankind. As exemplified by the UN Sustainable Development Goals, it has a tremendous potential for innovation and growth in blue economy sectors. Due to the inherent complexity of the natural system, the answers to man...
Integration of observations of the coastal ocean continuum, from regional oceans to shelf seas and estuaries/deltas with models, can substantially increase the value of observations and enable a wealth of applications. In particular, models can play a critical role at connecting sparse observations, synthesizing them, and assisting the design of ob...
To understand and predict the physical, chemical, and biological processes at play in coastal and nearshore marine areas requires an integrated, interdisciplinary approach. The case study of the French structuration of coastal ocean and nearshore observing systems provides an original overview on a federative research infrastructure named ILICO. It...
In the north-east Atlantic Ocean, the Bay of Biscay is an intersection between a coastal constrained dynamics (wide continental shelf and shelf break regions) and an eastern boundary circulation system. In this framework, the eddy kinetic energy is 1 order of magnitude lower than in western boundary systems. To explore this coastal complex system,...
The frontal activity in coastal regions remains a research field where a large number of open questions needs to be addressed to quantify the potential impact of these processes on dependent systems (e.g. biogeochemical activity). Spatial and seasonal distributions of Sea Surface Temperature (SST) fronts (∼1-100 km) in the vicinity of main French r...
In the North-East Atlantic Ocean, the Bay of Biscay is an intersection between a coastal constrained dynamics (wide continental shelf and shelf break regions) and an eastern boundary circulation system. In this framework, the eddy kinetic energy is one order of magnitude lower than in western boundary systems. To explore this coastal complex system...
Since January 2009, two long-range high-frequency (HF) radar systems have been collecting hourly high-spatial-resolution surface current data in the southeastern corner of the Bay of Biscay. The temporal resolution of the HF radar surface currents permits simulating drifter trajectories with the same time step as that of real drifters deployed in t...
Designing optimal observation networks in coastal oceans remains one of the major challenges towards the implementation of future efficient Integrated Ocean Observing Systems to monitor the coastal environment. In the Bay of Biscay and the English Channel, the diversity of involved processes (e.g. tidally-driven circulation, plume dynamics) require...
In the Bay of Biscay and the English Channel, in situ observations represent a key element to monitor and to understand the wide range of processes in the coastal ocean and their direct impacts on human activities. An efficient way to measure the hydrological content of the water column over the main part of the continental shelf is to consider shi...
Recent advances in Coastal Ocean Forecasting Systems (COFS) are discussed. Emphasis is given to the integration of the observational and modeling components, each developed in the context of monitoring and forecasting in the coastal seas. These integrated systems must be linked to larger scale systems toward seamless data sets, nowcasts and forecas...
Spatial and Seasonal Distributions of Frontal Activity over the French continental shelf in the Bay of Biscay observed from satellite Sea Surface Temperature
In a context of global change, ocean regions as the Bay of the Biscay and the English Channel represent key domains to estimate the local impact on the coasts of these evolutions. Indeed, the coastal (considering in this project regions above the continental shelf) and regional (including the continental slope and the abyssal plain) environments ar...
The aim of this study is to better understand the different overriding mechanisms that control the evolution of the hydrology and the circulation in the Bay of Biscay, through realistic regional simulations over a period of 50 years and to understand the effect of increasing the spatial resolution on the balances in the Bay of Biscay.
Before perfo...
The aim of this study is to better understand the different overriding mechanisms that control the evolution of the temperature in the Bay of Biscay, through realistic simulations over a period of 50 years. Before performing and analyzing our own numerical experiments with a spatial resolution of 4 km, we compared two global simulations, ORCA-G70 a...
Observing submesoscale activity in the Bay of Biscay with satellite-derived SST and Chlorophyll concentration
VACUMM is an open-source Python library for processing data from observations and numerical models. The library is now used for several years in research and operational contexts, for instance for producing figures and reports, validating models, converting data, or making simple or advanced diagnostics. In this paper, we introduce how the library...
consultable à l'adresse suivante : http://archimer.ifremer.fr/doc/00197/30785/29143.pdf
Two HF Radar CODAR SeaSonde stations are working operationally in the south-eastern Bay of Biscay since 2009 (Fig. 1). The HF radar stations are emitting at a central frequency of 4.86 MHz and provide hourly surface currents with 5 km radial and 5° angular resolutions and a 150 km mean radial coverage. The examination of 3 year HF radar data reveal...
Two Seasonde type high frequency (HF) radars have measured the surface currents in the southeastern part of the Bay of Biscay off the coast of Spain from 2009 to present. The radars are located at Cape Matxitxako and Cape Higer and operate at 4.86 mHz with a 40 kHz bandwidth, and provide hourly current measurements with a 5 km spatial resolution. T...
In April–November 2009, surface salinity data provide a good coverage of most of the south-east Bay of Biscay and nearby Aquitaine/Armorican shelves. By late April most of the shelf, in particular south of 46°N, is covered by a fresh surface layer amounting to a fresh water volume of 49·109m3. At that time, a moderate amount of fresh water has spre...
The presence of a quasi-stationary anticyclonic eddy within the southeastern Bay of Biscay
(centred around 44º30’N-4ºW) 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...
High Frequency (HF) radar stations have been working operationally in the southeastern part of the Bay of Biscay since 2009. The (2) systems provide hourly surface currents, with 5 km spatial resolution and a radial coverage lying close to 180 km. The detailed and quantitative description of the spatial patterns observed by the HF radar offers new...
Daily time series of in-situ tide gauge records and river runoff data were analysed to investigate the contribution of river discharge storm events to sea level in the Bay of Biscay. Three main river systems were considered for this study, representing cases of small (Nervión, 1900 km2), medium (Adour, 16880 km2) and large (Gironde, 84811 km2) wate...
Dinophysis is the most harmful toxic phytoplankton on the French coast in terms of its impact on local econ-omy and public health. In Arcachon Bay, Dinophysis spp. have periodically affected shellfish industry for the last ten years; the most important events are analysed in detail in this paper. Regular monitoring revealed that these events origin...
A study of sequential data assimilation of satellite derived sea surface temperature (SST)
in the free surface hydrodynamic model MARS-3D [Lazure and Dumas, 2008] using
Ensemble Kalman Filter [Evensen, 2003] is presented with application to the English
Channel and the shelf of the Bay of Biscay. We focused our efforts on summer 2006, when
observati...
In WP9 the evaluation of existing and future coastal observational platforms will be performed by applying
Observational System Experiments (OSEs) and Observational System Simulation Experiments (OSSEs) that
use data assimilation systems based on high resolution coastal ocean models. Data assimilation systems
cover a wide range of European coastal...
Based on Lagrangian drifter trajectories collected from 1992 to 2009, a seasonal climatology of the circulation in the Bay of Biscay has been computed. The buoys deployed during several cruises are fitted with drogues at depth between similar to 15 m and similar to 80 m to follow the current in surface layers. After a pre-processing of the dataset,...
The present study focuses on the spatial and temporal variability of interactions between physics and biogeochemistry during the Rossby wave passage in the South Atlantic Ocean. The Rossby wave signature in sea level anomalies (SLA) and surface chlorophyll a concentration anomalies (CHLA) is analyzed using remotely sensed data from 1997 to 2006. Wa...
An eddy-permitting coupled ecosystem-circulation 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 impac...
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,...
How do Rossby waves influence primary production in the North Atlantic Ocean? Rossby waves have a clear signature on surface chlorophyll concentrations which can be explained by a combination of vertical and horizontal mechanisms (reviewed in Killworth et al., 2004). In this study, we aim to investigate the role of the different physical processes...
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 chloroph...
Rossby waves signatures on filtered ocean color data are detected in the subtropical convergence zone of the South Atlantic ocean. We investigate whether these chlorophyll anomalies can be accounted for by the uplifting mechanism of phytoplanktonic cells associated with the passage of a Rossby wave. We consider vertical chlorophyll profiles exhibit...
Enhancement of surface chlorophyll-a by Rossby waves has been recently detected by several authors in ocean color data. The present study focuses on the South Atlantic ocean at mid-latitudes to detect such Rossby waves in satellite data (ocean color and altimetric data).The weekly SeaWIFS data and combined TOPEX/ERS data sets over the 3 years 1998-...
The marine phytoplankton in the ocean represents only less than 1% of global biomass. Phytoplankton performs half of all photosynthesis. This autotrophic biomass in ocean is then an essential element in the climate regulation through processes as carbon dioxide absorption during the photosynthesis. Therefore, we need to estimate precisely this biom...
Projects
Projects (6)
Analyze and understand the currents, the hydrological structure, and exchanges in the coastal systems. For this high frequency fixed points time series, recording in an Eulerian framework using different platforms in the French coasts, are analyzed. This includes measurements of temperature, salinity, fluorescence, turbidity, and other quantities such as dissolved oxygen or pCO2. The sampling frequency is below one hour, e.g. from 10 minutes to one hour.
