Application of anthropogenic uranium radioisotopes in tracing water mass movement in the Arctic-North Atlantic Ocean

• Main Author: Lin, Gang
• Format: Book
• Language: English
• Published: Technical University of Denmark 2023
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/climate_action; name=SDG 13 - Climate Action; /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; name=SDG 14 - Life Below Water; Arctic; Arctic Ocean; Barents Sea; North Atlantic; Sea ice
• Online Access: https://orbit.dtu.dk/en/publications/1efcf218-fd53-4dfa-ac60-f951f95db13e; https://backend.orbit.dtu.dk/ws/files/351258994/Gang_Lin-PhD_Thesis_DTU_Sustain_.pdf

A faster decline of sea ice extent in the Arctic in recent years is caused by the rapid warming of global climate. The northward Atlantic water carries a large amount of heat from the lower latitudes of the North Atlantic Ocean, and the release of heat in the Arctic Ocean plays a key role in the sea ice melting process. Atlantic water losses the heat to be cold and dense and thus sinks to deep water layer in the Arctic and subpolar region. Colder and deeper dense water outflows back into the North Atlantic Ocean, and this circulation is defined as the Atlantic Meridional Overturning Circulation (AMOC). It is one of important part of global thermohaline circulation, which profoundly contributes to global climate. Therefore, insights on the transport pathways and timescales of Atlantic water in the Arctic and North Atlantic oceans are significant for understanding the AMOC and the influence on melting of sea ice. Anthropogenic uranium (U) isotopes, namely 233 U and 236 U, are promising oceanic tracers owning to their long half-lives and conservative behavior in the open ocean, and their transient signals are useful to investigate water mass movement in a large spatial scale. Unique point-source signal from nuclear reprocessing plants (NRPs) at Sellafield (SF) and La Hague (LH) of European coast is herein exploited to study the transport of Atlantic water in the Arctic and North Atlantic oceans. Combining nutrients, salinity, colored dissolved organic matter (CDOM) and 99 Tc, two 233 U- 236 U tracer approaches were developed to estimate Atlantic water transit time. The first approach estimated the transit time of Atlantic water through comparing the original NRPs-derived 236 U ( 236 U NRPs ) concentrations in seawater sample and the reconstructed historic concentrations in three 236 U NRPs input functions at the Barents Sea Opening ( Paper I ). CDOM helps distinguish different Atlantic branch waters based on the terrestrial-derived and marine-derived CDOM, and therefore constrains the corresponding input functions ...