- 1Nansen Environmental and Remote Sensing Center, Bergen, Norway (yanchun.he@nersc.no)
- 2Department of Environmental and Resource Engineering, Technical University of Denmark, Roskilde, Denmark
- 3Norwegian Research Center, Bergen, Norway (emje@norceresearch.no)
- 4Bjerknes Center for Climate Research, Bergen, Norway
- 5Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China (linmu@mail.iggcas.ac.cn)
The pathways and time scales of Atlantic Water (AW) transport to the Arctic Ocean (AO), and its subsequent return to the North Atlantic, are critical for understanding the ocean’s role in modulating heat, salinity, and the sequestration of anthropogenic trace gases.
To quantify the time scales of AW transport by advective and diffusive processes, we applied the Inverse-Gaussian Transit-Time Distribution (IG-TTD) method, utilizing a suite of radionuclide datasets. The IG-TTD parameters—mean transit time (Γ), representing advection, and width (Δ), characterizing diffusion—were derived from radionuclides such as Iodine-129 (I-129), Technetium-99 (Tc-99), and Uranium-236 (U-236). These radionuclides originate primarily from two European nuclear reprocessing facilities. To complement observational data, idealized tracers from an ocean general circulation model (OGCM) were incorporated, including Boundary Impulse Response (BIR) tracers and dilution tracers. BIR tracers constrained the mixing ratio (Δ/Γ) in the IG-TTD, while the dilution tracer refined source functions for improved accuracy.
Preliminary results indicate a transit time of approximately 25 years from the Iceland-Scotland Ridge to the central Arctic Ocean, with mixing ratios (Δ/Γ) ranging between 0.2 and 0.4—significantly lower than the typical value of ~1 observed for CFCs/SF6 tracers transitioning from surface ventilation to the ocean interior. A dilution factor on the order of 1000 was necessary to scale source functions and avoid unrealistically high mean ages. Transit times showed substantial variability within the same region, depending on radionuclide type and sampling period, highlighting the impact of strong synoptic variability in ocean currents on measurement uncertainties. Additionally, dual-tracer constraints on mixing ratios, comparisons of transit times derived from radionuclides versus ventilation tracers, and assessments against model-simulated BIR tracers are discussed.
How to cite: He, Y., Lin, M., and Jeansson, E.: Estimated Transport of Atlantic Water to the Arctic Ocean Using Observed and Simulated Radionuclides, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13327, https://doi.org/10.5194/egusphere-egu25-13327, 2025.
