GROUND TRUTHING THE CD CA-CARBON ISOTOPE RELATIONSHIP IN FORAMINIFERAOF THE GREENLAND-ICELAND-NORWEGIAN SEAS/

In order to examine whether the paleoceanographic nutrient proxies, de lta(13)C and cadmium/calcium in foraminiferal calcite, are well couple d to nutrients in the region of North Atlantic Deep Water formation, w e present data from two transects of the Greenland-Iceland-Norwegian S eas. Along Transect A (74.3 degrees N, 18.3 degrees E to 75.0 degrees N, 12.5 degrees W, 15 stations), we measured phosphate and Cd concentr ations of modern surface sea water. Along Transect B (64.5 degrees N, 0.7 degrees W to 70.4 degrees N, 18.2 degrees W, 14 stations) we measu red Cd/Ca ratios and delta(13)C Of the planktonic foraminifera Neoglob oquadrina pachyderma sinistral in core top sediments. Our results indi cate that Cd and phosphate both vary with surface water mass and are w ell correlated along Transect A. Our planktonic foraminiferal delta(13 )C data indicate similar nutrient variation with water mass along Tran sect B. Our Cd/Ca data hint at the same type of nutrient variability, but interpretations are hampered by row values close to the detection limit of this technique and therefore relatively large error bars. We also measured Cd and phosphate concentrations in water depth profiles at three sites along Transect A and the delta(13)C Of the benthic fora minifera Cibicidoides wuellerstorfi along Transect B. Modem sea water depth profiles along Transect A have nutrient depletions at the surfac e and then constant values at depths greater than 100 meters. The delt a(13)C of planktonic and benthic foraminifera from Transect B plotted versus depth also reflect surface nutrient depletion and deep nutrient enrichment as seen at Transect A, with a small difference between int ermediate and deep waters. Overall we see no evidence for decoupling o f Cd/Ca ratio and delta(13)C in, foraminiferal calcite from water colu mn nutrient concentrations along these transects in a region of North Atlantic Deep Water formation. (C) 1997 Elsevier Science B.V.