Sea surface temperature reconstruction based on planktonic foraminifera of surface sediments and sediment cores off Iberia

Quantitative and qualitative analyses of planktonic foraminiferal assemblages from 134 core-top sediment samples collected along the western Iberian margin were used to assess the latitudinal and longitudinal changes in surface water conditions and to calibrate a Sea Surface Temperature (SST) transfer function for this seasonal coastal upwelling region. Q-mode factor analysis performed on relative abundances yielded three factors that explain 96% of the total variance: factor 1 (50%) is exclusively defined by Globigerina bulloides, the most abundant and widespread species, and reflects the modern seasonal (May to September) coastal upwelling areas; factor 2 (32%) is dominated by Neogloboquadrina pachyderma (dextral) and Globorotalia inflata and seems to be associated with the Portugal Current, the descending branch of the North Atlantic Drift; factor 3 (14%) is defined by the tropical-sub-tropical species Globigerinoides ruber (white), Globigerinoides trilobus trilobus, and G. inflata and mirrors the influence of the winter-time eastern branch of the Azores Current. In conjunction with satellite-derived SST for summer and winter seasons integrated over an 18 year period the regional foraminiferal data set is used to calibrate a SST transfer function using Imbrie & Kipp, MAT and SIMMAX(ndw) techniques. Similar predicted errors (RMSEP), correlation coefficients, and residuals' deviation from SST estimated for both techniques were observed for both seasons. All techniques appear to underestimate SST off the southern Iberia margin, an area mainly occupied by warm waters where upwelling occurs only occasionally, and overestimate SST on the northern part of the west coast of the Iberia margin, where cold waters are present nearly all year round. The comparison of these regional calibrations with former Atlantic and North Atlantic calibrations for two cores, one of which is influenced by upwelling, reveals that the regional one attests more robust paleo-SSTs than for the other approaches.

Biogeochemical properties of sinking particles intercepted at three depths on the NW Atlantic margin

Three conical sediment were deployed at three depths 968 m (top trap), 1976 m (middletrap), and 2938 m (50mabove the bottom, bottom trap) - from June 27, 2004 to April 27, 2005 on the NW Atlantic margin at a water depth of 2988 m. The sediment trap carousels were programmed to open each collection cup for 23.4 days for the top trap and 14.5 days for the other two traps, resulting in total 13 samples from the top trap and 21 samples each from the middle and bottom traps. The samples were analyzed for the biogeochemical properties with various methods. Frequent occurrences of higher fluxes in deep relative to shallower sediment traps and low delta 14C values of sinking POC together provide strong evidence for significant lateral transport of aged organic matter over the margin. Comparison of biogeochemical properties such as aluminum concentration and flux, and iron concentration between samples intercepted at different depths shows that particles collected by the deepest trap had more complex sources than the shallower ones. These data also suggest that at least two modes of lateral transport exist over the New England margin. Based on radio carbon mass balance, about 30% (± 10%) of sinking POC in all sediment traps is estimated to be derived from lateral transport of re-suspended sediment. A strong correlation between delta 14C values and aluminum concentrations suggests that the aged organic matter is associated with lithogenic particles.