The distribution of dissolved inorganic iodine in the seas around Iceland

Depth profiles for iodide, iodate and total dissolved inorganic iodine concentrations were measured in the ocean around Iceland during November 2000, and February and August 2002. Meanwhile surface transects of the same variables were taken between the coast and about 100 nm offshore. Overall, the results are consistent with the general pattern for iodine distribution. Hence, total iodine was essentially constant with depth except for a small removal (up to 20 nM) in surface waters, and the greatest effect was that of reduction of iodate to iodide in the near-surface waters. The magnitude of the reductions was similar to that reported for the Antarctic, and as there, was less than in surface waters nearer the equator. These measurements are only the second set made in Arctic waters and reasons are given as to why they should supersede the earlier ones. The distributions found in northerly moving Gulf Stream water were not significantly different to those found in southerly moving modified Arctic water at the same latitude. A provisional budget of iodine inputs and outputs for the Nordic Seas also suggests little or no overall change in iodine speciation. These results reinforce the contention that iodine distribution is a zonal phenomenon. Nutrient measurements made at the same time as the iodine study show a marked nutrient stripping during summer, and regeneration/replenishment during autumn and winter. These findings therefore add further evidence to the fact that, in higher latitudes, there is no link between iodine speciation and new production.