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GOG Ocean Characteristics: COASTAL UPWELLING

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GOG Ocean Characteristics: COASTAL UPWELLING Map showing the Gulf of Guinea in the Central Eastern Atlan6c. The Gulf of Guinea is that part of the Eastern Tropical Atlantic Ocean off the western African coast, extending westward from Cap López, near the Equator, to Cape Palmas at longitude 7° west. GOG ocean characteris6cs Gulf of Guinea Region showing prevailing ocean currents Guinea Current flowing southward along the coast of the Gulf of Guinea is essentially a continuation of the Equatorial Counter‐Current. Coastal Ocean currents in the G O G consist of the Guinea current, which is an extension of the North Equatorial Counter current. GOG ocean characteriscs: WATER INPUT A major influence on the region is the input of freshwater from the numerous rivers in this relatively high‐rainfall region, most notably the Niger and Zaire. This results in large masses of warm (above 24°C) and low salinity (less than 35 ppt). GOG OCEAN CHARACTERISTICS: SST The Gulf of Guinea region of the tropical Atlantic has the largest SST seasonal amplitude of between 5‐8°C. A coastal upwelling is observed each year along the northern coast of GOG. GOG ocean characteriscs: CURRENT REVERSALS A reversal in current direction has been detected during the minor upwelling. Avon Mahi 10 canyo n This change is attributed to 0 n mud m coast variations in the flow of the North Equatorial Countercurrent, the Canary Current, and the Benguela Current, and to the weakening of the easterly winds. Atlan4c Ocean These changes are also known to affect plankton production and the seasonal migration of fish and weather patterns which comprise of dry and wet seasons. Trajectory of drier No 26122 deployed off the Benin River estuary in the western Niger Delta.(Awosika and Folorunsho 2008 In press). GOG ocean characteristics: COASTAL UPWELLING Coastal upwelling No coastal upwelling on observed on15 July 15 July 2006 in the same 2005 area (Bourles 2008) Coastal upwellings observed on 15 July 2005 but not observed on 15 July 2006 in approximately the same area in the GOG. (Bourles 2008) COASTAL UPWELLINGS IN THE GULF OF GUINEA Two upwelling seasons: TWO MAIN COASTAL UPWELLING -Main season from June to September; REGIONS: -Minor upwelling (January to March. 1-Côte d’Ivoire-Ghana 2-Congo-Gabon -A remarkable characteristic? -No evident correlation between wind forcing and coastal temperature during the major upwelling season. => Alternative mechanisms have been suggested (mainly for the Côte d’Ivoire- Ghana upwelling): -Current induced upwelling -Cape effect -Remote forcing by trapped Kelvin waves, -etc. (Source: courtesy of Claude Roy, IRD) IMPORTANCE OF SEA SURFACE TEMPERATURE (SST AND SALINITY IN THE GULF OF GUINEA (Bourles et. al. 2007) Comparison of SST between June 10, 2005 (leJ picture) and June 10 2006 (right picture) in the Gulf of Guinea (TMI). Sea surface temperature (SST) in the Gulf of Guinea vary at seasonal and inter‐annual time scales and thus may have a strong impacts on regional climate consisting of the West African monsoon onset and intensity, precipitation (water resources), and fisheries. More data and studies on coastal upwelling variability and its impacts ! ONGOING PROGRAMMES TO UNDERSTAND SST, SSS AND MET OCEAN PROCESSES IN THE GOG PIRATA PIRATA with 10 atlas buoys in the Atlantic Ocean; 5 are managed by IRD, located at (0°E‐0°N) Figure : Pilot Research moored Array in the Tropical Atlan4c ONGOING PROGRAMMES CONTI.. Argo Argo activities in the GOG region so far has trained oceanographer and technicians in the deployment and retrieval of Argo data. On the 12 March 2008, ARGO float was deployed in the GOG (at 0.02°S and 0.15°E) as part of a hands‐on training for African scientists on board the US. Navy vessel HSV-2 Swift. AMMA‐EGEE (REGIONAL PROGRAM OF PHYSICAL OCEANOGRAPHY IN WEST AFRICA, (RIPIECSA ‐ PROPAO) AMMA / EGEE cruises in the 6 cruises: - June-July 2005, 2006 & 2007 Gulf of Guinea ) AMMA / - September 2005, November 2006, September 2007. EGEE cruises in the Gulf of Guinea EGEE 3 - 2nd Leg As part of the AMMA – EGEE- Stations CTD 4oN XBT XCTD PROPAO Programme: the coastal o 0 observation network developed as an 4oS extension of the open ocean studies has 8oS installed three SST autonomous 12oS 15oW 10oW 5oW 0o 5oE 10oE 15oE sensors (ONSET) in Ivory Coast, Ghana, Nigeria, Togo and Benin. INITIAL RESULTS FROM PROPAO ACTIVITIES Sea temperature (ONSET thermometer) time evolution at Cotonou, from July 2005 to August 2007 (raw data) Coastal waters warmer in winter/spring 2006 than in 2007 (>1,5°C) Autonomous thermometers (onset) ONGOING PROGRAMMES CONTI.. WMO INITIATIVES IN THE REGION An ongoing pilot project on marine meteorology and remote sensing (involving three countries Senegal, Cape Vert and Mauritania) is at its final stage for implementation. The project would contribute to the needs expressed by the countries in the region to improve marine meteorological services for maritime safety and fisheries management. Strengthening the capacity of Member States to manage oceanographic data and information (with special attention to the developing countries) and to provide ocean data and information products and services required by users. JCOMM/IOC/IODE Combined Modeling and Data Management Training Workshop ("Jamboree"), Ostend, Belgium, 5-10 September 2005 and 2006. In the GOG region, as well as other regions JCOMM has facilitated the compilation of existing information and guidance on met ocean observations and services. OTHER ONGOING PROGRAMMES ODINAFRICA (Ocean Data and Information Network for Africa) Building an Ocean Data and Information Network for Africa. Increased the number of NODCs in Africa from 4 to 18 in the past 2 years. Equipped with computers, and training is provided in the collection and management of the data. GOOS AFRICA (Global Ocean Observations System) Guinean Current - Large Marine Ecosystem (GCLME) Though some work and understanding of the SST, SSS and coastal upwelling in the GOG area have been done carried out by the different program areas, the region still lacks behind on the long term data that could be used to fully understand these processes . A coordinated SST programme for the GOG should be put in place. Special activities of the GOG SST and SSS under the GOSUD/SAMOS programme should include: •Coordination of all on-going SST and SSS activities in the GOG area. •Collating of existing long term SST and SSS data in the region •Analysis of data to expose long term variability's in SST (PRODUCTS ?). •Publication of the results of the activity •Continuous capacity development of local scientists in the lunching retrieval of data, analysis and interpretation of data. These programms should include: •EGEE, PROPAO •PIRATA, •Ocean Data and Information Network for Africa (ODINAFRICA, IOC/UNESCO), •JCOMM •Global Ocean Observation System (GOOS)-Africa, •Guinean Current - Large Marine Ecosystem (GCLME) The GOSUD/SAMOS Programme is a laudable programme for understanding and determining the status of SST, SSS observing network (data collection, assembly, gaps, QC). This programme presents a viable lunching pad for an integrated approach for the inclusion of the GOG in the programme. While the region has a modest set of scientists that can be included in decision making activities in this programme there exist a moderately young group of scientists and technicians that can be brought onboard. It must be understood that the objective of the GOSUD/SAMOS programme is to fully understand the ocean ( SST, SSS) among others, however this cannot be accomplished with regional data gaps. I acknowledge with thanks support from GOSUD/SAMOS Workshop Organizers and IRD-LEGOS/France & CRHOB/Benin for making my participation possible. .
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