Wavelet analysis on upwelling index along the Moroccan Atlantic coast

Wavelet analysis is a relatively new technique, an enormous interest in the application of wavelets has been observed in the recent years. In this paper, we use the wavelet analysis on the upwelling index based on sea surface temperature data from 1993 to 2014 along the Moroccan Atlantic coast, mainly at Cape Cantin, Cape Ghir, Cape Juby, Dakhla and Cape Blanc. We noticed that from Jan 1993 to Oct-1998 and from Sep-2007 to Nov 20014, the upwelling in the five research latitudes increases with fluctuations. The period of Upwelling varies sensitively with the change of time scale. The value of upwelling index in the five latitudes appears similar and present an obvious period of one year in all latitudes studied. This study can be considered an important tool for time series analysis, which can help the studies concerning the upwelling variability

Un Demi Siècle D’évaluation De L’activité De L’upwelling De La Côte Atlantique Marocaine

Les écosystèmes d'upwelling situés en bordures Est (EBUEs) sontparmi les écosystèmes les plus productifs au monde et leur réponse auchangement climatique d'une importance cruciale. La variabilité saisonnièreet décennale à long terme de l'activité d'upwelling de la partie nord du grandécosystème marin du Courant des Canaries (CCLME) a été étudiée dans cetravail sur une période de 53 ans (1967-2019) à deux stations situéesrespectivement au nord (31°N-10,5°O) et au sud (24,5°N-15,5°O) de la côteatlantique marocaine, en élaborant l’Indice d’Upwelling de Bakun (UI)mensuel. Les résultats obtenus montrent que l’upwelling présente unevariabilité saisonnière entre Cap Juby - Larache et une activité quasipermanente toute l’année entre Cap Juby - Cap Blanc. En relation avec lavariabilité décennale et dans la zone nord atlantique marocaine, les plus fortesactivités de l’upwelling ont été observées en saisons d’été, en particulier surla période 1998-2003 et son activité a légèrement dépassé la moyenne sur lespériodes 1972-1977, 1980-1984, 2004-2008. Les plus faibles activités del’upwelling dans cette zone ont été observés en saisons d’automne/hiver,notamment sur les périodes 1967-1970, 1995-1998 et 2000-2005. S’agissantde la zone sud atlantique marocaine, l’activité de l’upwelling a présenté uneforte activité de l’upwelling en été sur les périodes 1967-1980 et 2009-2019,avec des fluctuations annuelles à interannuelles variables entre ces deuxpériodes. Cette activité a été légèrement supérieure à la moyenne en été sur lapériode 1981-2007, sauf pour les années 1982-1983, 1988-1989, 1995-1997et 2004-2007 où il a été observé une relative tendance vers la baisse. De plus faibles activités de l’upwelling ont été observées dans cette zone sur la période2003-2010 en saisons d’automne/hiver. Eastern Boundary Upwelling Ecosystems (EBUEs) are among themost productive ecosystems in the world, meaning that their response toclimate change is of critical importance. In this work, we investigate the longterm seasonal and decadal variability of the upwelling activity along thenorthern part of the Canary Current Large Marine Ecosystem (CCLME) overa period of 53 years (1967-2019). Two stations were selected in this studyrepresentative of the upwelling activity in the moroccan atlantic coast, one inthe north (31° N-10.5°W) and the other in the south (24.5° N-15.5°W) usingthe monthly Bakun Upwelling Index (UI). The results shows a seasonalvariability in the northern region of morocco between Cap Juby - Larache andalmost permanent activity all year round in the southern region of moroccobetween Cap Juby - Cap Blanc. These results are consistent with previousstudies based on the seasonality of the upwelling regime in thisregion. Relatedto the decadal variability, the strongest activities of upwelling were observedduring summer seasons in the northern region, in particular over the periodv 1998-2003 and its activity slightly exceeded the average over the periods1972-1977, 1980-1984, 2004-2008. The weakest upwelling activities in thisregion were observed in the fall-winter seasons, particularly during the periods1967-1970, 1995-1998 and 2000-2005. In the southern region, the upwellingactivity showed strong upwelling activity in summer over the periods 1967-1980 and 2009-2019, with annual and interannual between these two periods.This activity was slightly above average in summer over the 1981-2007period, except for the years 1982-1983, 1988-1989, 1995-1997 and 2004-2007where a relative downward trend was observed. Lower upwelling activitieswere observed in this area over the 2003-2010 period in fall / winter seasons

CIRCULATION MARINE DE LA LAGUNE DE NADOR (MAROC) PAR MODELISATION HYDRODYNAMIQUE

The marine circulation of Nador lagoon (Morocco) have been studied from April to July 2011 by hydrodynamic 3D model, under the new configuration of its new inlet which is operational from 2011. This study aims to understand the new mode of hydrodynamic functioning of this lagoon. The circulation in the lagoon is wind driven circulation, as the wind is contributing to mixing internally the lagoon waters. During the neap tides, the surface currents are very strong in the new inlet (> 1 m.s-1), less than 0.5 m.s-1 in the centre and 0.3 m.s-1 near the continental sides of the lagoon. The bottom currents are in the opposite direction from the surface currents and less than 0.2 m.s-1

Chapter Phytoplankton assemblage Characterization along the Mediterranean coast of Morocco during autumn

The present study aimed to assess the composition, abundance and diversity of phytoplankton assemblage along the Moroccan Mediterranean Coast. Phytoplankton samples were collected in October 2018 at 48 stations from M’diq bay in the West to Saïdia in the East. 92 taxa have been inventoried, belonging to five groups. Diatoms dominate qualitatively and quantitatively (85.5%), followed by dinoflagellates (12%). Phytoplanktonic diversity and abundance was pronounced in the western part of Moroccan Mediterranean Sea, especially (from Jebha to M’diq) because of the influence of the Atlantic flow

Marine Circulation along the Moroccan Atlantic Coast

As part of the Canary Current Ecosystem, numerical models from Marine Copernicus are used to study the seasonality of marine circulation along the Moroccan Atlantic coast from 2007 to 2017. Therefore, we explore the marine circulation in three areas according to the wind seasonality along the coast. The first area, 33°N-35°N, is specified all the year by a low wind speed. The second area, 28°N-33°N, is characterized by a seasonal wind with the maximum speed in summer seasons, and it becomes weaker in autumn seasons. Finally, the third area, 21°N-27°N, is marked all the seasons by high winds intensity. Due to the Moroccan Atlantic coast topography, the average intensity of marine circulation on the surface is characterized by different trends according to the seasons. Part of the seawater, creating filaments, is exported to the open sea, especially in summer. Marine circulation affects the upwelling process under the effect of seasonal wind patterns. These filaments are identified near the coast and are particularly strong when the upwelling is active. They occur mainly in summer and carry cold, nutrient-rich water offshore. In addition, counter-currents appear at different depths, depending on the topography of the region. They move northward, especially near the coast in spring and fall

Long Term Upwelling Activity along the Moroccan Atlantic Coast

The long term activity of the upwelling along the Moroccan Atlantic coast between Cape Blanc (21°N) and Cape Spartel (36°N) is investigated in this work using a monthly Ekman Upwelling Index over the period 1967-2019 (53 years). Three stations that are representative of the upwelling’s activity along the Moroccan Atlantic coast from North to South were selected in this study for analysis: ST5 (31°N-10.5°W) between Cape Sim and Cape Ghir, ST7 (29°N-10.5° W) between Cape Ghir and Cape Draa and ST12 (24.5°N-15.5°W) North Dakhla between Cape Boujdor and Cape Barbas. The results show a seasonal variability in the northern area between Cape Juby – Cape Spartel and a permanent activity mostly all the year in the southern area between Cape Juby - Cape Blanc. Strongest activities of upwelling were observed during summer seasons in the northern area, in particular over the period 1998-2003, and its activity slightly exceeded the average over the periods 1972-1977, 1980-1984, 2004-2008.  The weakest upwelling activities in this region were observed in the fall-winter seasons, particularly during the periods 1967-1970, 1995-1998 and 2000-2005. In the southern area, the upwelling variations showed strong upwelling activity in summer over the periods 1967-1980 and 2009-2019, with annual and interannual variability between these two periods. This activity was slightly above average in summer over the 1981-2007 period, except for the years 1982-1983, 1988-1989, 1995-1997 and 2004-2007 where a relative downward trend was observed. Lower upwelling activities were observed in this area over the 2003-2010 period in fall /winter seasons

Caractérisation Hydrologique et Sédimentaire de la Lagune de Nador (Maroc)

Une prospection océanographique a été réalisée dans la lagune de Nador, située sur la côte méditerranéenne marocaine, en Juillet 2012 dont l’objectif est l’étude de l’état hydrologique et sédimentaire de la lagune après la mise en place de la nouvelle passe en 2011. La distribution des paramètres physico-chimiques du milieu ont permis la mise en évidence une variabilité spatiale en relation avec la circulation générale dans la lagune et la présence de la station d’épuration sur la rive continentale. L’état sédimentaire observé témoigne de l’intensité de l’échange mer-lagune qui est élevée au centre par comparaison aux extrémités NO et SE. Ainsi, le maintien de l’équilibre environnemental de cet écosystème dépend du degré d’échange mer-lagune et le contrôle de l’impact des activités anthropiques. An oceanographic survey was carried out in the Nador lagoon located on the Moroccan Mediterranean coast, in July 2012. The objective is to study the hydrological and sedimentary state of the lagoon after the establishment of the new pass, in 2011. The distribution of the physicochemical parameters of the environment allowed the identification of a spatial variability in relation to the general circulation in the lagoon and the presence of the treatment station on the continental shore. The sedimentary state also shows the intensity of the sea-lagoon exchange which is elevated in the center compared to the NO and SE extremities. Thus, maintaining the environmental balance of this ecosystem depends on the degree of sea-lagoon exchange and the control of the impact of anthropogenic activities

Variabilite Oceanographique De La Zone D’el Jadida – Jorf Lasfar (Maroc)

Une campagne océanographique côtière a été réalisée en Juillet 2018 entre El Jadida et Jorf Lasfar. Cette zone est caractérisée par la présence d'algues rouges et présente une bathymétrie très régulière de la côte à l’isobathe 20m. Les paramètres océanographiques collectés au cours de cette mission montrent que la colonne d'eau est bien stratifiée avec des eaux froides riches en nutriments au fond et relativement plus chaudes et déficientes en nutriments en surface. La zone étudiée est très influencée par la forte concentration des phosphates provenant des rejets de Jorf Lasfar. Durant la période de la campagne, la stratification verticale pourrait s’expliquer par la faible activité des résurgences des eaux froides profondes. Malgré cette stratification, la colonne d'eau était bien saturée en oxygène dissous aussi bien en surface qu’au fond. A coastal oceanographic cruise was carried out on July 2018 between El Jadida and Jorf Lasfar. This area is characterized by the presence of red algae and presents a very regular bathymetry from the coast to isobaths 20m. The collected oceanographic parameters during this cruise show that the water column is well stratified with cold waters rich in nutrients at the bottom and relatively warmer and deficient in nutrients on the surface. The area study is very influenced by the high concentration of phosphates originated from Jorf Lasfar. During this summer’s period, the vertical stratification could be explained by the low activity of the resurgences of cold deep waters. Despite this stratification, the water column is well saturated on dissolved oxygen both on the surface and at the bottom

Circulation Marine de la Baie de Cintra (Sud du Maroc) par Modèle Hydrodynamique 2D

The marine circulation of Cintra bay located at Dakhla Oued Eddahab area (south of Morocco 23°08’N-16°20’W) has been studied from October to November 2016 by 2D hydrodynamic model. This study aims to understand the marine circulation of this bay and its hydrodynamic functioning. Mainly governed by wind and semidiurnal M2 tides, currents are generally strong in intensity (mainly > 0.5 m.s-1 ) outside the bay. Inside the bay, their intensity are less than 0.3 m.s-1 and generally oriented to the south of the bay due to the influence of the trade winds (NE). Due sometimes to the influence of W and/or SW winds, the coastal circulation of the bay is oriented from the south to the north, impacting its northern part

Structure, diversity and habitat characterization of Copepods from the Cape Ghir upwelling, Morocco

The zooplankton, of the Cape Ghir filament area in Morocco (31°N), was sampled during five oceanographic cruises conducted between 2008 and 2009. Physical and chemical parameters were measured. In total, 11 stations were sampled on two radial perpendiculars: one latitudinal (31°N) with 7 stations coast-large and the other longitudinal (10°09' W) with 5 stations North-South. The intersection between the two radial corresponds to station 4. Copepods constitute the largest fraction of zooplankton community and represented by 86 species. The temporal variability in the copepod community structure showed that the dominant species listed may change their dominance during the study period. Their composition could be analyzed for changes in community structure associated with oceanographic variation with statistical analysis. The relation between the distribution of copepods species and the environment parameters, shows that some species (Paracalanus parvus, Oncaea venusta, Acartia clausi, Oithona nana and Euterpina acutifrons) are mainly correlated with chlorophyll 'a' and nutrients. However, other species (Oithona plumifera, Oithona similis and Clausocalanus arcuicornis) are correlated with temperature and salinity. Eight copepods species “Acartia clausi, Calanus helgolandicus, Neocalanus gracilis, Oithona nana, Oithona similis, Oithona plumifera, Oncaea venusta and Paracalanus parvus” are characterized by their high frequency and their dominance in all periods and were analyzed specially with their relation to the hydrological parameters to determinate their Environmental Preference Habitat. The global quotients were calculated in relationship with each of the hydrological and productive parameters; considered as the most influencing on the distribution of these species. Moreover, the temperature and the chlorophyll 'a' seem to be the most important factors in the determination of the copepod’s habitats in Cape Ghir area