Global fallout and continuous liquid releases by the two European Nuclear Reprocessing Plants of Sellafield (Great Britain) and La Hague (France) are the major contributors of artificial radionuclides to the Arctic and North Atlantic Oceans. Anthropogenic 236U and the 236U/238U ratio are becoming a new transient tracer in oceanography, which combined to 129I (129I/236U ratio) can be used as a novel oceanographic tool in the Arctic and North Atlantic Oceans. Main strengths of using 129I/236U and 236U/238U atomic ratios are: i) identify sources of artificial radionuclides in water masses (global fallout, reprocessing plants and/or rivers); and ii) evaluating water mass ages. Here we will present results from different GEOTRACES expeditions in the Arctic and North Atlantic Oceans during the years 2011 – 2015, including the two pan-arctic expeditions onboard German RV Polarstern and US RV Healy. Seawater samples and ice cores are analyzed for 129I and 236U, contributing to a better understanding of the general Arctic water circulation and their further transport to the North Atlantic Ocean.