The applicability of the T/S method to geopotential anomaly computations in the Northeast Atlantic

Methods are tested for computing geopotential anomalies from temperature data in the subtropical Northeast Atlantic. Mean temperature-salinity, salinity-depth and density-depth relationships are determined for 3 x 3° squares, using hydrographie data from World Oceanographie Data Centre A. Geopotential anomalies computed from observed temperatures and salinities from these mean relationships are compared with anomalies from the original temperature and salinity data. For 0-500 dbar, geopotential anomalies can be weil approximated, and the methods also work reasonably weil for 0-1000 dbar. The approximation is poor for 0-2000 dbar. Appropriate methods for obtaining the best results in each 3 x 3° square are specified. The method is applied to a particular subset of the data

3. Wochenbericht M90

Meteorreise M90 Cristobal, Panama nach Callao, Peru 3. Wochenbericht (05.11.-11.11.2012

3. Wochenbericht M77/4

Der vierte Fahrtabschnitt der METEOR-Expedition M77/4 findet vom 27. Januar bis 18. Februar 2009 im küstennahen Auftriebsgebiet vor Peru unter Fahrtleitung von Dr. Lothar Stramma (IFM-GEOMAR) statt. Forschungsschwerpunkt sind hydrographische und chemische Untersuchungen. Es soll detailliert vermessen werden, wie die Wassermassen im südöstlichen tropischen Pazifik heute verteilt sind und wie stark die Sauerstoffminimumzone ist. Dies geschieht vorrangig mit dem Ziel, Änderungen zu früheren Verteilungen festzustellen. Zum anderen soll die Verteilung geochemischer Komponenten in der Wassersäule erfasst werden. FS Meteor Reise M77/4 4. Fahrtabschnitt Callao, Peru – Colon, Panama 3. Wochenbericht (8.2.-18.2.2009

Geostrophic transport in the Warm Water Sphere of the eastern subtropical North Atlantic

Geostrophic transports in the eastern subtropical North Atlantic computed from historic hydrographic data and recent CTD measurements show a mean transport in the subtropical gyre of 11 ± 1.5 × 106 m3 s–1 in the upper 1000 m between 35W and the African coast. The dynamic method was used in conjunction with a conservation of mass scheme (Fiadeiro and Veronis, 1982) to determine the level of no motion. This level lies in the 1200 m depth near the Azores and drops to 1500 m in the tropics. The main inflow enters south of the Azores as a relatively narrow current, turns southward at the latitude of Madeira and then widens. Three current bands transport the water southward. North of the Cape Verde Islands, the current turns westward. This part of the North Equatorial Current extends more to the south in the upper 200 m than in the 200–800 m layer. The Portugal current, between the Azores and the Portuguese coast, which is thought by some to be strong, is seen here as a relatively weak flow. Maps of potential vorticity derived from smoothed density profiles are consistent with the general pattern of geostrophic transport

2. Wochenbericht M90

Meteorreise M90 2. Wochenbericht (29.10.-4.11.2012) Cristobal, Panama nach Callao, Per

Geostrophic transport of the South Equatorial Current in the Atlantic

Geostrophic transport calculations from historical data of the equatorial South Atlantic are presented for the investigation of the flow field in the South Equatorial Current region. On the basis of water mass distribution, the potential density surface of sigma-1 = 32.15 kg m-3 is used as a reference for geostrophic shears. This reference surface is located at a depth of 1000 to 1200 m and represents the boundary between the upper branch of the Circumpolar Deep Water and the Upper North Atlantic Deep Water. The southern band of the South Equatorial Current (SSEC) is fed by the Benguela Current, which crosses the Greenwich Meridian south of 20S. West of the Greenwich Meridian the subtropical gyre has its northermost current band as the westward flowing SSEC. The SSEC was found to be a broad sluggish flow between 10S and 25S. The transport of the SSEC in the upper 500 m is in the order of 20 Sv, with surface velocities of around 10 cm s-1. At 30W the SSEC turns northward. A small part of the water turns poleward south of 10S to form the Brazil Current, whereas the bulk of the flow contributes to the North Brazil Current and the South Equatorial Countercurrent (SECC). The SECC seems to cross the entire South Atlantic eastward to at least the Greenwich Meridian, but part of the flow might contribute to the middle branch of the South Equatorial Current flowing westward. The northernmost current band sampled is the eastward flowing South Equatorial Undercurrent. From this data no seasonality in the geostrophic field can be proven

4. Wochenbericht M90

Meteorreise M90 Cristobal, Panama nach Callao, Peru 4. Wochenbericht (12.11.-18.11.2012

Zirkulation und Klimavariabilität des tropischen Atlantiks = Circulation and climate variability in the tropical Atlantic ; Fahrtbericht / Cruise Report SO151 KLIIMAZIIRKEL (BMBF Projekt 03G0151A), Bridgetown - Recife, 1. - 27. November 2000

RV "SONNE" cruise So151, during 1 to 27 November 2000 from Bridgetown, Barbados to Recife, Brazil was carried out by the Institut für Meereskunde Kiel within the contect of the international CLIVAR (Climate Variability and Predictability) projects. The work was a contribution of the german ocean-CLIVAR (Sub-project "tropical-subtropical interaction") program of Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF). One main aim of the sub-project is the investigation of the climate relevance of the shallow tropical-subtropical circulation cell in the equatorial Atlantic and its focus in the western boundary current off Brazil. The main objectives beneath the CLIVAR related research in the upper ocean were investigations of the deep sea circulation. In the upper ocean the interaction between the tropical water circulation an the subtropical North Atlantic in the late phase of the northern summer was one particular objective. Some goals of it were the measurements of transports of warm water off the coast towards the Caribbean, the existence and structure of the equatorial Undercurrent as part of the northern hemispheric shallow thermohaline cell and its focus in the western boundary current. Objectives of the deep circulation are the spreading of North Atlantic Deep Water (NADW) at and across the equator, as well as the recirculation in the Guyana-Basin and the expected arrival of a strong pulse of Labrador Sea Water at the equator. Measurements carried out were high resolution measurements of temperature, conductivity, pressure and oxygen by CTD casts, continuous current profiling in the upper 500 m of the water column using shipboard Acoustic Doppler Current Profiler (ADCP), top to bottom velocity profiles from an ADCP lowered with the CTD, freon distribution from the Niskin bottles and continuous surface temperature and salinity distributions, meteorological parameters and depth soundings. In addition 2 moorings were recovered and redeployed and 5 profiling floats were deployed. The cruise was carried out in close co-operation with So152 (Prof. M. Rhein) and So153 (Prof. U. Send) who also carried out CLIVAR investigations. The sections perpendicular to the coast will be worked up together with the ones from So152 to investigate large scale water mass and circulation distributions