The R/V Johan Hjort 1994 NORDIC WOCE cruise: On hydrography and tracers

Abstract

Results from hydrographical and halocarbon tracer measurements during an oceanographic expedition with the Norwegian R/V Johan Hjort to the Norwegian Sea, the Faroe Bank Channel, the Iceland and the Irminger Basins and the Iceland Sea are presented. Special attention has been given the overflow waters over the Iceland-Scotland ridge and through the Denmark Strait. While the Denmark Strait overflow does not mix significantly with surrounding waters during its descent into the Irminger Basin, the Iceland-Scotland overflow is signiticantly entrained by ambient waters within the Iceland Basin. By multivariate analysis using Principal Component Analysis (PCA) and Partial Least Square (PLS) calibration, it can be concluded that the overflow water masses contain onlv minor fractions of the bottom waters in the Norwegian and the Iceland Seas, respectively, which means about one fourth Norwegian Sea Deep Water (NSDW) over the Iceland-Faroe ridge, while, over the sill in the Denmark Strait, the fraction of Iceland Sea Bottom Water (ISBW) is about one third. CFC tracers were used to assign apparent ages of water masses, showing that the NSDW has an apparent age of about 30 years and the ISBW has an apparent age of more than 25 years. Through the deepest parts of the Faroe Bank Channel flows water with an apparent age of about 20 years with an origin at about 1000 m depth in the Norwegian Sea. Labrador Sea Water (LSW) with an age of around 20 years was found in the Iceland Basin, while the LSW in the Irminger Basin is significantly younger, two cores were found, one of an age of 11-12 years underlain by a 6 years younger core. The Northeast Atlantic Bottom Water in the lceland Basin, which has an Antarctic origin, was observed circulating cyclonically within the basin.