Beschreibung: Highlights: • Unique data set of daily temperature and current measurements over almost 30 years. • Cooling of the thermocline in the 1980s and extensive warming in the 2000s. • Currents indicate northward displacement of N-Atlantic subtropical Gyre in 1990s. • Influence of NAO and ENSO on current regime even in 500 m water depth. Data from almost thirty years of time series observations from a deep-sea mooring Kiel276 (33°N, 22°W), which was operated in the northeast Atlantic Ocean between 1980 and 2009, are studied to reveal information on the long term changes in the upper thermocline. This includes daily records of temperature and currents at two depths (240 m and 500 m). Until 1988, our analysis shows decreasing temperature in the entire thermocline followed by a slight increase at both depths; from 2000 on, extensive warming began at the shallower depth (240 m) and eight years later at the deeper (500 m) level. A northward displacement of the North Atlantic Subtropical Gyre is indicated by both current measurements and calculated kinetic energy between 1991 and 1998 resulting in an altered current regime in terms of absolute velocity and current directions in the last ten years compared to the first twenty years. Coherences of the currents with large scale climatic patterns such as North Atlantic Oscillation and El Niño/ Southern Oscillation evidence the atmospheric impact even at 500 m water depth.

Beschreibung: In the framework of the German contribution to the Joint Global Ocean Flux Study (JGOFS), deep-water fluxes of particle-associated trace elements were measured in the northeast Atlantic Ocean. The sinking particles were collected almost continuously from 1992 to 1996 at three time-series stations, L1 (33 degrees N/22 degrees W), L2 (47 degrees N/20 degrees W), and L3 (54 degrees N/21 degrees W), using sediment traps. The focus of the present study is the temporal variability of the particle-associated elemental fluxes of Al, Ca, Cd, Co, Cu, Fe, Mn, Ni, P, Pb, Ti, V, and Zn at a depth of 2000 m. A clear seasonality of the fluxes that persisted for several years was documented for the southernmost station (L1) at stable oligotrophic conditions in the area of the North Atlantic Subtropical Gyre East (NASTE). At L2 and L3, an episodic nature of the elemental fluxes was determined. Mesoscale eddies are known to frequently cause temporal and spatial variability in the flux of biogenic components in that area. These events modified the simple seasonal pattern controlled by the annual cycle at L2, in the North Atlantic Drift Region (NADR), and at L3, which was influenced by the Atlantic Arctic province (ARCT). All stations were characterized by an additional episodic lithogenic atmospheric supply reaching the deep sea. The integrated annual fluxes during the multi-year study revealed similar flux magnitudes for lithogenic elements (Al, Co, Fe, Ti, and V) at L2 and L3 and roughly twofold fluxes at L1. Biogenic elements (Cd, P, and Zn) showed the opposite trend, i.e., two to fourfold higher values at L2 and L3 than at L1. For Mn, Ni, and Cu, the spatial differences were smaller, perhaps because of the intermediate behavior, between lithogenic and biogenic, of these elements. Similarly, among the three study sites, there were no noticeable differences in the total annual flux of Pb. The respective lithogenic fractions of the deep-sea fluxes of Cd, Co, Cu, Mn, Ni, V. and Zn were subtracted based on the amount of Al, with the average composition of the continental crust as reference. This procedure allowed estimation of the labile trace element fraction (TE(exc)) of the particles, i.e., TE taken up or scavenged during particle production and sedimentation. The ratios of TE(exc)/P clearly demonstrated an enrichment of TE over labile P from biogenic surface material to the deep sea for Zn (factor 4-6), Mn (12-27), Ni (3-5), and Cu (9-25); an intermediate status for Co (0.5-2.2); and depletion for Cd vs. P (0.2-0.4). Surprisingly, the recycling behavior of excess Co was found to be similar to that of P. Hence, Co(exc), behaved like a biogenic element; this is in contrast to total Co, which is dominated by the refractory lithogenic fraction. Moreover, it is argued that these excess elemental fluxes caused a loss of the dissolved elements in upper waters, since their transport reaches the deep-sea waters at 2000 m, a depth far below of deep-winter mixing and upwelling. The annual amount of excess TE exported from surface waters was estimated to be 1.3 x 10(9) mol Zn y(-1), 4.4 x 10(9) mol Mn y(-1), 4.9 x 10(8) mol Ni y(-1), 2.2 x 10(7) mol Cd y(-1), 7.4 x 10(8) mol Cu y(-1), and 2.7 x 10(7) mol Co y(-1) for the whole North Atlantic Ocean. Important primary sources that could replenish these losses are the aeolian and fluvial supply processes. (C) 2010 Elsevier Ltd. All rights reserved.