Description: Particle flux data from 27 sites in the Atlantic Ocean have been compiled with a view to determining regional variations in the strength and efficiency of the biological pump and quantifying basin-wide fluxes and estimating the potential oceanic sequestration of atmospheric CO2. An algorithm is derived relating annual particulate organic carbon (POC) flux to primary production and depth that yields variations in the Export Ratio (ER = POC FLUX/Primary Production) at 125 m of between 0.1 and 0.4 over the range of production from 50 to 400 gCm-2 yr-2. Significant regional differences in changes of the ER with depth are related to the temporal stability of flux. Sites with more pulsed export have higher shallow ERs and show more rapid degradation of particulate organic carbon (POC) flux with depth, resulting in little variation in fluxes below ca. 3000 m. The opposing effects of organic carbon production and calcification on pCO2 of surface seawater are combined to calculate an "effective carbon flux" at the depth ofeuphotic zone and at the base of the winter mixed layer. POC flux at the base of the euphotic zone between 65°N and 65°S amounts to 3.14 Gt C yr-1, of which 5.7% is remineralised above the winter mixed layer, and is thus not available to sequestration on climatically relevant time scales. The effective carbon flux, termed Jeff, amounts to 2.47 Gt C yr-1 and is a measure of the potential sequestration of atmospheric CO2 for the area considered. A shift in the composition of sedimenting particles (opal: carbonate ratio) is seen across the entire North Atlantic, indicating a basin-wide phenomenon that may be related to large-scale changes in climatic forcing.

Description: 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.