C-14 and Ar-39 in the Arctic Ocean P. Schlosser, B. Ekwurzel, G. Boenisch in cooperation with B. Kromer, H. G. Oestlund, H. H. Loosli, R. Purtschert, A. McNichol, R. Schneider, K. von Reden, J. H. Swift ON THE C-14 AND Ar-39 DISTRIBUTION IN THE CENTRAL ARCTIC OCEAN: IMPLICATIONS FOR DEEP WATER FORMATION P. Schlosser, B. Kromer, H. G. Oestlund, B. Ekwurzel, G. Boenisch, H. H. Loosli, R. Purtschert RADIOCARBON, Vol. 36, No. 3, 1994, P. 327-343 Abstract We present Delta C-14 and Ar-39 data collected in the Nansen, Amundsen and Makarov basins during two expeditions to the central Arctic Ocean (RV Polarstern cruises ARK IV/3, 1987 and ARK VIII/3 1991). The data are used together with published Delta C-14 values, to describe the distribution of Delta C-14 in all major basins of the Arctic Ocean (Nansen, Amundsen, Makarov and Canada Basins), as well as the Ar-39 distribution in the Nansen Basin and the deep waters of the Amundsen and Makarov Basins. From the combined Delta C-14 and Ar-39 distributions, we derive information on the mean "isolation ages" of the deep and bottom waters of the Arctic Ocean. The data point towards mean ages of the bottom waters of the Eurasian Basin (Nansen and Amundsen Basins) of ca. 250-300yr. The deep waters of the Amundsen Basin show slightly higher H-3 concentrations than thosa in the Nansen Basin, indicating the addition of a higher fraction of water that has been on the surface during the past few decades. Correction of the bomb C-14 added to the deep waters along with bomb H-3 yields isolation ages for the bulk of the deep and bottom waters of the Amundsen Basin similar to those estimated for the Nansen Basin. This finding agrees well with the Ar-39 data. Deep and bottom waters in the Canadian Basin (Makarov and Canada Basins) are very homogeneous, with an isolation age of 450 yr. Delta C-14 and Ar-39 data and a simple inverse model treating the Canadian Basin Deep Water (CBDW) as one well mixed reservoir renewed by a mixture of Atlantic Water (29%), Eurasian Basin Deep Water (69%) and brine enriched shelf water (2%) yield a mean residence time of CBDW of ca. 300 yr. Figure Ar-39 concentrations observed in the Arctic Ocean. The numbers indicate the station number and the average Ar-39 concentration (in % modern; the uncertainty is the error of the mean value of up to three replicate measurements) The first trans-Arctic 14C section: comparison of the mean ages of the deep waters in the Eurasian and Canadian basins of the Arctic Ocean Peter Schlosser, Bernd Kromer, Brenda Ekwurzel, Gerhard Boenisch, Ann McNichol, Robert Schneider, Karl von Reden, H.G. Oestlund, and J.H. Swift NIM Abstract We present Delta C-14 data collected during three cruises to the Arctic Ocean that took place in the summers of 1987 (POLARSTERN cruise ARK IV/3), 1991 (ARCTIC 91 Expedition), and 1994 (Arctic Ocean Section 94). The cruise tracks of these three expeditions cover all major basins of the Arctic Ocean (Nansen, Amundsen, Makarov, and Canada basins), and can be combined to a trans-Arctic section reaching from the Barents Sea slope to the southern Canada Basin just north of Bering Strait. The section is based on 16 stations covering the entire water column (about 250 data points). The combined Delta C-14 data set was produced from a mixture of large volume samples measured by low-level counting and small volume samples measured by Accelerator Mass Spectrometry (AMS). We use the Delta C-14 section, together with previously published Delta C-14 data from single stations located in several basins of the Arctic Ocean, to derive information on the deep water formation rates in the Arctic Ocean. A remarkable feature of the Delta C-14 section is the homogeneity in the C-14 distribution observed in the deep Canadian Basin. Within the measurement precision of about ±2ä (LV) to about ±5ä (AMS), we cannot detect significant horizontal or vertical Delta C-14 gradients below 2,000 meters depth between the northern boundary of the Makarov Basin and the southern margin of the Canada Basin. There is no statistically significant difference between samples measured by AMS and by low-level counting. Figures ! Geographical positions of the C-14 stations used in the Delta C-14 section shown below. The positions of the ice stations LOREX and CESAR, as well as of the stations occupied by the icebreakers Polar Star (1992) and Sir John Franklin (1989) are also indicated. Trans-Arctic section of potential temperature containing data from three cruises (Polarstern cruises Ark IV/3 and ARK VIII/3; Louis St. Laurent cruise AOS 94). The potential temperature sections of the individual cruises are published in Anderson et al, 1987 (Polarstern 1987 cruise), Anderson et al., 1991 (Arctic 91 expedition) and Aagaard et al., 1996 (AOS 94 section). Trans-Arctic Delta C-14 section containing data obtained from stations occupied during two cruises of RV Polarstern (ARK IV/3, 1987;ARK VIII/3, 1991), and in the framework of the AOS 94 section from the Louis St. Laurent (for geographical positions, see above). .