Description: During January and February 1989 the recirculation of the subtropical gyre in the eastern North Atlantic was surveyed with a three-ship experiment. The analysis of hydrographic measurements and velocity data from a shipboard acoustic Doppler current profiler reveals the synoptic-scale circulation patterns and water mass distributions in the Canary Basin. The geostrophic transport stream function estimated with a horizontally varying reference level of no motion highlights the major currents in three layers representing the vertical structure of the horizontal circulation. The classical circulation scheme is shown by the stream function in the upper 200 m: the Azores, Canary, and North Equatorial currents. Unlike the deep-penetrating Azores Current, the Canary Current and the North Equatorial Current are restricted to the upper 200 m. Both carry North Atlantic Central Water along the water mass boundary with South Atlantic Central Water. South Atlantic Central Water flows through the passage between the Cape Verde archipelago and Africa via narrow currents into the area north of 14.5°N. At the southern edge of the subtropical gyre we identify an eastward flow of Antarctic Intermediate Water between 700 and 1200 m.

Description: Time series of currents from an array of 22 subsurface moorings in the Canary and Iberian Basins of the North Atlantic are analyzed with respect to low-frequency variability. The record lengths are usually 1 to 2 years but almost 9 years (site KIEL276, 33N, 22W) in one case. Maximal energies are observed at periods between 50 and 500 days, and high-energy events are found from time to time. The 9-year long series indicates changes in currents with a 3-4 year period, primarily in the zonal component, and anisotropic energy distributions are found for both current components at periods around 200 days. The vertical structure can be well approximated by the barotropic and first-order baroclinic dynamical modes or by one empirical orthogonal function. The regional distribution of spectral properties indicates higher energies in frontal zones and in the neighborhood of the Canary archipelago. In general, the kinetic energy in the month-to-year variability is lower than in the western basins of the North Atlantic.

Description: Eastern Boundary Upwelling Ecosystems (EBUEs) are associated with high biological productivity, high fish catch and they highly contribute to marine carbon sequestration. Whether coastal upwelling has intensified or weakened under climate change in the past decades is controversially discussed and different approaches (e.g., time-series of chlorophyll, wind, sea surface temperature, modeling experiments) have been considered. We present a record of almost two decades of particle fluxes (1991–2009) from ca. 600 to 3100 m water depth in the Canary Basin at site ESTOC (European Station for Time series in the Ocean Canary Islands; ca. 29°N, 15°30.W, ca. 3600 m water depth), located in the offshore transition zone of the northern Canary Current-EBUE. We compare these flux records with those measured at a mesotrophic sediment trap site further south off Cape Blanc (Mauritania, ca. 21°N). The deep ocean fluxes at ESTOC in ca. 3 km recorded the evolution of the coastal Cape Ghir filament (30–32°N, 10–12°W) due to lateral advection of particles, whereas the upper water column sediment traps in ca. 1 km reflected the oligotrophic conditions in the overlying waters of ESTOC. We observed an increased emphasis in spring-time fluxes since 2005, associated with a change in particle composition, while satellite chlorophyll biomass did not show this pattern. Due to its northern location in the CC-EBUEs, spring biogenic fluxes at ESTOC provide a better relationship to the forcing of the North Atlantic Oscillation than those recorded further south off Cape Blanc. Off Cape Blanc, deep fluxes showed the best overlap with the deep ESTOC fluxes during the spring season before 2005. On the long-term, both chlorophyll and particle fluxes showed an increasing trend at ESTOC which was not observed further south at the mesotrophic Cape Blanc site. This might indicate that, depending on their location along the NW African margin, coastal upwelling systems react differently to global change.

Description: This report is thought as a guide to early hydrographic log sheets of bottle data obtained by the former Institut für Meereskunde, Kiel (IFMK, now integrated into GEOMAR) in the post-war years 1946 to 1956, and which in summer 2018 when a building used by GEOMAR was to clear were not available in digitized format at GEOMAR. The data mostly were taken by the research cutter FK “Südfall” in the Baltic. It turned out that some of these data from 1950 to 1956 were available in digitized form at the on-line data bank of the International Council for the Exploration of the Sea (ICES). Comparison with the original logged data sheets, however, showed that they needed to be improved w/r to time and position and to be completed by missing data. This report shortly describes the methods of sampling and measuring these old data, and the processing steps applied to improve the data set by using the data log sheets before archiving and submitting the now improved and complete data set to data centres for archiving.

Description: Highlights: • Unique 30-years data of currents and temperature below 1000 m in the Madeira Basin. • Inter-decadal and long term changes were examined between 1000 m and the bottom. • Temperature increase by 0.03 ± 0.01 °C/year (1000 m) and 0.02 ± 0.02 °C/year at 1600 m. • No significant changes at 3000 m and 5000 m at long-term scale. • The currents and kinetic energy increased in the entire water column over 30-years. Abstract: Data from the deep-sea mooring Kiel 276 (33 N, 22W), 5300 m water depth in the northeast Atlantic, was used to investigate the temporal variability of temperature and currents below the main thermocline (1000 m, 1600 m, 3000 m, 5000 m) in the 30-year period (between 1980 and 2009). Daily averages were the basis to assess the temperature and currents changes, as well as kinetic energy, from annual to decadal and long-term scales. Below the main thermocline, no seasonal signal was identified for both, temperature and currents, during the 30 years. The record-length linear temperature trends at 1000 m and 1600 m are 0.03 ± 0.01 °C year−1 and 0.02 ± 0.02 °C year−1, respectively. The mean currents also intensified within the decades in the entire water column, and as a consequence, the mean kinetic energy increased. The fluctuating kinetic energy increased on a decadal scale only at 1000 m, as a possible consequence of the increase in the strength of Mediterranean Water lenses (MEDDIES) that crossed the mooring site. During the period 2001–2009, six MEDDIES crossed the Kiel 276 site, in addition to the 10 MEDDIES identified earlier during the previous 20 years, between 1980 and 2000 (Siedler et al., 2005). The integral time scales are of the same order in all depths (between 30 to 40 days), indicating that events occur on similar time scales, with mesoscale signals dominating and being present within the entire water column.