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

We present Δ¹⁴C 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 17 stations covering the entire water column (about 250 data points). The combined Δ¹⁴C 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 Δ¹⁴C section, together with previously published Δ¹⁴C data from single stations located in several basins of the Arctic Ocean, to derive mean "ages" (isolation times) of the deep waters in the Arctic Ocean. We estimate these mean "ages" to be ≈ 250 years in the bottom waters of the Eurasian Basin and ≈ 450 years in the Canadian Basin Deep Water. A remarkable feature of the Δ¹⁴C section is the homogeneity in the ¹⁴C distribution observed in the deep Canadian Basin. Within the measurement precision of about ±2‰ (LV) to about ±5‰ (AMS), we cannot detect significant horizontal or vertical Δ¹⁴C gradients below 2000 m 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.