GOGforMETOCSea FINAL

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A Staff METOC Officer’s Guide for the Gulf of Guinea (GOG) Region: An Oceanographic Perspective: 

1 A Staff METOC Officer’s Guide for the Gulf of Guinea (GOG) Region: An Oceanographic Perspective 1 Produced, in part, for completion of MR 4250 Course Project by: Maj. Rob LeeJoice, LT Jackie Crook, LT Christi Montgomery & LT Andy O’Neill UNCLASSIFIED

Outline: 

2 Outline Definitions of key climate terms General characteristics Bottom topography Marine biology Ocean characteristics (SST, SWH, SSH, etc) Currents ALERT!: Additional information can be found in the notes portion of most slides in this presentation. UNCLASSIFIED

Slide3: 

3 Reanalysis - The analysis of climate system components using modern analysis processes to analyze past states of the climate system. Reanalysis is the same as standard atmospheric or oceanic analysis, except that it is not done in real time, and it involves consistent analysis procedures applied to all times in the reanalysis period (e.g., the background field is made by an NWP model that does not change over the entire period of the reanalysis). A serious problem with climate change studies based on standard operational analyses results from frequent changes in the algorithms, assimilation schemes, and model used to generate the analysis fields. These changes (including changes in resolution and orography) lead to discontinuities in a time series of real-time analyses. A reanalysis yields complete, global gridded data that are as temporally homogeneous as possible. Reanalysis fields are a major source of climate information since they fill in many of the spatial and temporal gaps in observations of the climate system, and are typically done for multi-year or multi-decadal periods. Reanalysis data include many derived fields (heating, soil moisture over land, etc.) for which direct observations are nearly absent. Many operational organizations generate reanalyses of the atmosphere and ocean for use in climate studies, including NOAA, AFCCC, NASA, ECMWF, NRL, and universities. Definitions Slide from Module 5 of Modern Climatology course, Dr. T. Murphree (murphree@nps.edu) Many of the graphs in this presentation were produced using a “Reanalysis” data set. It is important to understand how this differentiates the results presented here and previous, or Long Term Mean information. UNCLASSIFIED

Slide4: 

4 Long Term Mean (LTM) - The mean of many observations collected over a long period of time. The standard period for calculating a LTM is 30 years. LTMs are commonly based on observations made at the same location and same time of day but at many different dates (e.g., T at 00Z on 01 January of 30 consecutive years). LTMs are common and very useful quantities in climatology. But they do not represent many important temporal aspects of the climate system, such as trends and oscillations. These are better represented by other types of means and by higher order statistical quantities (e.g., select composite means, variance, standard deviation, temporal clusters, principal components). Seasonal Cycle or Annual Cycle - The annual cyclical pattern in climate system variables caused by the seasons. This cycle is based on long term means for each day of the year, and represents the mean variation from day to day throughout the course of the year. Thus, the seasonal or annual cycle of a variable can be represented by a time series of daily LTMs. From G: That component of variability that is a function of the day of the year but is independent of the year. S5, T96, etc - The letter represents the parameter (T-temperature, S-salinity) and the number represents the depth in meters. Ex: S5 is the salinity at 5m in depth JFM/JAS – January, February, March and July, August, September Definitions (cont’d) Slide from Module 5 of Modern Climatology course, Dr. T. Murphree (murphree@nps.edu) UNCLASSIFIED

Slide5: 

5 Oceanic Reanalysis Data Set Used: Simple Ocean Data Assimilation (SODA), version 1.4.2: - Spatial coverage: ~global (0-360E, 75.25S-89.25N) - Temporal coverage: 1958-2001, 44 years - Horizontal resolution: variable but ~ 0.3 x 0.3 degrees * - Vertical resolution: 40 levels, from 5 m to 5374 m 10 levels in the upper 100 m 20 levels in the upper 500 m - Observational input variables: surface winds, T, S, SSH, heat and freshwater fluxes - Reanalyzed output variables: x, y, SSH, T, S, u, v - Model based on Parallel Ocean Program numerics and similar to z level models used by multiple researchers - Data analyzed: 528 individual monthly means, Jan58–Dec01 horiz res: 0.5 x 0.5 degrees all levels, but focus on upper 500 m base period for calcualting LTMs: 1968-1996 Slide information from: ASW Smart Climo, Aug 07, murphree@nps.edu Ocean Modeling SODA ALERT! – More info in the notes section! UNCLASSIFIED

Focus Regions For GOG Oceanography: 

Focus Regions For GOG Oceanography 20°W – 10°E & 5°S – 5°N UNCLASSIFIED

General Characteristics: 

7 General Characteristics Volcanic Islands off the coast that formed 38 million years ago Predominantly shallow water off the coast to about 2000-3000m in depth Several rivers and waterways contribute to sediment runoff (the major ones being Niger and Congo Rivers) Established as a Large Marine Ecosystem (see details in notes) Region regarded as one of the world’s top oil and gas exploration hot spots Figure from: http://commons.wikimedia.org/wiki/Image:Gulf_of_Guinea_(English).jpg Volcanic Islands Principe Islands Spotted Dolphin http://www.ggcg.st/jon_principe.htm ALERT! – More info in the notes section! UNCLASSIFIED

More General Characteristics : 

8 More General Characteristics Continental margins originated from the separation of Africa from South America ~180 million years ago. Generally narrow continental shelf Shelf break occurs at average of 100m in depth Coast is mostly sandy and surf-beaten shorelines Most of the coastal basins contain oil and gas fields Figure from: http://oceancurrents.rsmas.miami.edu/atlantic/img_topo1/guinea2.jpg UNCLASSIFIED

Bottom Topography: 

9 Bottom Topography Predominance of sand, silt and shells in bottom deposits Topography and oceanic conditions of the Continental shelf affect the distribution and composition of fish communities Figure from http://oceancurrents.rsmas.miami.edu/atlantic/guinea_2.html Figure from Regional oceanography text by Tomczak and Godfrey. UNCLASSIFIED Depth in meters

Marine Biology: 

10 Marine Biology Humpback whales Leatherback turtles Arctic terns (bird) Smaller fish (sardines, anchovies, etc) Southern pink shrimp Figure from: http://na.nefsc.noaa.gov/lme/text/lme28.htm#productivity Arctic Tern http://www.douglloydphotography.com/mediac/400_0/media/Arctic~Tern~533.jpg UN Food and Ag. Organization 10yr Trend of catch composition in the GoG Large Marine Ecosystem #28 http://woodsmoke.edc.uri.edu/Portal/jsp/data_bathy.jsp UNCLASSIFIED ALERT! – More info in the notes section!

Salinity Characteristics : 

11 Salinity Characteristics Dry Season in Tropical W. Africa Wet Season in Tropical W. Africa 37 36 35 34 33 32 Congo River Delta Niger River Delta Figures created using the SODA ocean reanalysis data set (with SODA details provided in slide 5).  UNCLASSIFIED ALERT! – More info in the notes section! Salinity measurement is in parts per thousand at 5 meters depth. Influences on Salinity include; fresh water river run-off, precip. over the ocean, evaporation from the ocean and advection of water from remote regions. The lowest salinity values in each season generally exist near the coast of Africa. A larger contribution to salinity modification along the Guinea coast occurs in the dry season (DJFM). See atmosphere and land briefs for more information on river run-off.

Ocean Surface Characteristics : 

12 Sea Temperatures are shown here to range from less than 14° (at 96m) to greater than 25°C (at 5m) during January-February-March. There is a large decrease in temperature between 5m and 96m indicating a dramatic thermocline in the Gulf of Guinea during JFM. Ocean Surface Characteristics UNCLASSIFIED ALERT! – More info in the notes section! Figures created using the SODA ocean reanalysis data set (with SODA details provided in slide 5).  14° 25° South Equatorial Current

Ocean Surface Characteristics : 

13 Again, there is a large decrease in temperature between 5m and 96m indicating a dramatic thermocline in the Gulf of Guinea during July-August-September. Although the scales are different, some consideration will show that there is a dramatic rise in 5m temperatures from JFM to JAS. This contrast can be attributed to differing amounts of precipitation interseasonally as well as seasonal shift in surface current direction and magnitude (to be covered in later slides). Ocean Surface Characteristics UNCLASSIFIED ALERT! – More info in the notes section! Figures created using the SODA ocean reanalysis data set (with SODA details provided in slide 5).  South Equatorial Current 14° 25° 31° 21°

Temperature and Salinity Profiles for Point: 2.25N, 5.25E: 

14 Note 2-3o temperature difference at 5m between the seasonal profiles. At 40-50m, the temperature profiles are very similar with only a difference of 1o. The seasonal salinity profiles differ by 1 ppt from 5 to 40m, then are almost the same with increasing depth. Temperature and Salinity Profiles for Point: 2.25N, 5.25E UNCLASSIFIED ALERT! – More info in the notes section! Figures created using the SODA ocean reanalysis data set (with SODA details provided in slide 5).  Temperature (°C) Salinity(PSU) Δ=2+°C

Time Series of SST : 

15 Notice interannual variability in the time series, imposed on top of decadal variations for the “Wet Season” (JAS). Note: what may appear to be negligibly small SST changes (interannual variability can be important in a number of ways (e.g., small SST changes can lead to large changes in evaporation, specific and relative humidity, cloud formation, precip, upper ocean stability, vertical mixing, upwelling/downwelling, nutrient transport, primary productivity, fisheries, etc.).  The dry season also exhibits interannual variability, but it seems to be imposed upon a longer “decadal” periodicity than the “wet” and also exhibits a slight upward trend (.5 to 1°C). Time Series of SST WET SEASON DRY SEASON Figures from: http://www.cdc.noaa.gov/cgi-bin/Timeseries/timeseries1.pl UNCLASSIFIED ALERT! – More info in the notes section!

Slide16: 

16 LTM COMP MEAN Slightly higher SSTs extend along the GoG coast for the 5 driest seasons The high SSTs can be correlated to a lack of precip and thus contribute to drought conditions. (see precip slides in the GoG atmosphere brief) The entire region of interest experiences the same higher SSTs 5 Driest Seasons Composite Mean & LTM Figures from: http://www.cdc.noaa.gov/cgi-bin/Composites/printpage.pl UNCLASSIFIED

Slide17: 

17 LTM COMP MEAN Slight lower SSTs compared to the LTM along the GoG coast. The low anomalies can be a sign of higher precip, convective activity, etc. Higher SSTs north of the equator due to seasonal variability 5 Wettest Seasons Composite Mean & LTM Figures from: http://www.cdc.noaa.gov/cgi-bin/Composites/printpage.pl UNCLASSIFIED

Significant Wave Height Dry Season: 

18 Significant Wave Height Dry Season Figures created at https://navy.ncdc.noaa.gov/grads-servlet/indexsmgc.jsp DEC JAN FEB MAR Mean Significant Wave Height in Feet – Available from FNMOD Climatology Detachment’s Surface Marine Gridded Climatology (SMGC) Display System 0-2 Ft 2-3 Ft >3 Ft UNCLASSIFIED ALERT! – More info in the notes section!

Significant Wave Height Wet Season: 

19 Significant Wave Height Wet Season JUL AUG SEPT OCT UNCLASSIFIED Figures created at https://navy.ncdc.noaa.gov/grads-servlet/indexsmgc.jsp ALERT! – More info in the notes section! Mean Significant Wave Height in Feet – Available from FNMOD Climatology Detachment’s Surface Marine Gridded Climatology (SMGC) Display System 0-2 Ft 2-3 Ft >3 Ft

The GoG Current System: 

20 The GoG Current System From Regional oceanography text by Tomczak and Godfrey. Fig. 14.2. From Tomczak, M., and J.S. Godfrey, 1994(1941): Regional Oceanography: An Introduction. “Surface currents of the Atlantic Ocean. Abbreviations are used for the East Iceland (EIC), Irminger (IC), West Greenland (WGC), Loop (LC) and Antilles (AC) Currents and the Caribbean Countercurrent (CCC). Other abbreviations refer to fronts: JMF: Jan Mayen Front, NCF: Norwegian Current Front, IFF: Iceland – Faroe Front, SAF: Subarctic Front, AF: Azores Front, ABF: Angola – Benguela Front, BCF: Brazil Current Front, STF: Subtropical Front, SAF: Subantarctic Front, PF: Polar Front, CWB/WGB: Continental Water Boundary / Weddell Gyre Boundary. Adapted from Duncan et al. (1982), Krauss (1986) and Peterson and Stramma (1991).” ALERT! – More info in the notes section! UNCLASSIFIED

The Guinea Current: 

21 The Guinea Current Geostrophically balanced, eastern boundary current Notice the seasonal shift in direction of the Guinea Current Steep topography off the GoG coast causes it to head back towards the west as the South Equatorial current (Source http://oceancurrents.rsmas.miami.edu/atlantic/guinea.html ) Seasonal upwelling occurs along the GoG coast from early July through Sept Figures from: Guinea Current, GIWA Regional assessment 42. ALERT! – More info in the notes section! UNCLASSIFIED

The GoG Current System : 

22 The GoG Current System Note how the surface currents shift between the seasons Strong undercurrent flowing eastward towards the West African coast which is deeper during the wet season West African Coast West African Coast Figures created using the SODA ocean reanalysis data set (with SODA details provided in slide 5).  UNCLASSIFIED Cyclonic surface circulation Anticyclonic surface circulation

GoG Current System with SSH: 

23 GoG Current System with SSH The current vectors confirm the main features discussed in previous slides Note SSHs are more positive along the coast (same color scheme for both figures) Figures created using the SODA ocean reanalysis data set (with SODA details provided in slide 5).  UNCLASSIFIED

References: 

24 www.agu.org/pubs/crossref/2003/2002JB001928.shtml http://www.fao.org/DOCREP/003/S4639E/S4639E02.htm http://www.globalsecurity.org/military/ops/guinea-guard.htm http://www.iwlearn.net/iw-projects/Fsp_112799467056/guinea_termevaluation_1999.pdf/view http://na.nefsc.noaa.gov/lme/text/lme28.htm#productivity http://www.fao.org/docrep/003/w4248e/w4248e08.htm#AREA34 ENSO SIGNALS IN RELATION TO ASPECTS OF OCEAN CHARACTERISTICS ALONG THE GULF OF GUINEA COAST; *Folorunsho R. A, **Ojo S. O and *Awosika L. F. *Nigerian Institute for Oceanography and Marine Research. PMB 12729, Victoria Island , Lagos http://www.irinnews.org/IRIN-Africa.aspx https://navy.ncdc.noaa.gov/private/index.html Ocean Circulation, 2nd edition, The Open University, © 2001 pages 151-155 Regional Oceanography: An Introduction, Tomczak, M. and Godfrey J., pages 258-261. THE SEASONAL UPWELLING IN THE GULF OF GUINEA COAST DUE TO REMOTE FORCING; Adamec, D. and O’Brien, J. Dept of Meteorology and Oceanography Florida State University © 1978 UNEP, 2004. Abe, J., Wellens-Mensah, J., Diallo, O.S. and C. Mbuyil Wa Mpoyi. Guinea Current, GIWA Regional assessment 42. University of Kalmar, Kalmar, Sweden. http://oceancurrents.rsmas.miami.edu/atlantic/guinea.html Emergence of the Gulf of Guinea in the Global Economy: Prospects and Challenges, Damian Ondo Mañe. International Monetary Fund. © 2005 http://www.chez.com/gefgclme/ http://www.cdc.noaa.gov/Composites http://www.cdc.noaa.gov/Timeseries References UNCLASSIFIED

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