THE FIRST TRANS-ARCTIC C-14 SECTION - COMPARISON OF THE MEAN AGES OF THE DEEP WATERS IN THE EURASIAN AND CANADIAN BASINS OF THE ARCTIC-OCEAN

We present Delta(14)C data collected during three cruises to the Arcti c 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 S ea slope to the southern Canada Basin just north of Bering Strait. The section is based on 17 stations covering the entire water column (abo ut 250 data points). The combined Delta(14)C data set was produced fro m 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(14)C section, together with previously published Del ta(14)C data from single stations located in several basins of the Arc tic Ocean, to derive mean ''ages'': (isolation times) of the deep wate rs in the Arctic Ocean. We estimate these mean ''ages'' to be approxim ate to 250 years in the bottom waters of the Eurasian Basin and approx imate to 450 years in the Canadian Basin Deep Water. A remarkable feat ure of the Delta(14)C section is the homogeneity in the C-14 distribut ion observed in the deep Canadian Basin. Within the measurement precis ion of about +/- 2 parts per thousand (LV) to about +/- 5 parts per th ousand (AMS), we cannot detect significant horizontal or vertical Delt a(14)C gradients below 2000 m depth between the northern boundary of t he Makarov Basin and the southern margin of the Canada Basin. There is no statistically significant difference between samples measured by A MS and by low-level counting.