Rapidly Increasing Artificial Iodine Highlights Pathways of Iceland-Scotland Overflow Water and Labrador Sea Water

Iceland-Scotland Overflow Water (ISOW) and Labrador Seawater (LSW) are major water masses of the lower Atlantic Meridional Overturning Circulation (AMOC). Therefore, investigation their transport pathways is important to understand structure AMOC how climate properties exported from North latitudes. There growing evidence Lagrangian model simulations observations that ISOW LSW detach boundary currents spread off-boundary, into basin interior in Ocean. Nuclear fuel reprocessing facilities Sellafield La Hague have been releasing artificial iodine ( 129 I) northeastern since 1960ies. As a result, I supplied north Greenland-Scotland passages subpolar region labelling waters southward flowing AMOC. To explore potential as tracer pathways, we analyzed concentrations seawater collected during four oceanographic cruises subtropical regions between 2017 2019. The new showed deep maxima highlighted spreading along flanks Reykjanes Ridge, across fracture zones eastern supporting recent studies. Further, found intruding Ocean at unprecedented rate much larger extensions than past. This has enabled use for other purposes aside tracing ISOW. For example, increasing levels allowed us differentiate newly formed I-rich older vintages poorer content. concentration intermediate depths could be used track beyond far seas near Bermuda. Considering releases increased or levelled off last decades, it very likely invasion will continue providing opportunities future.