Circulation timescales of Atlantic Water in the Arctic Ocean determined from anthropogenic radionuclides
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Date
2021-01-18
Publication Type
Journal Article
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Abstract
The inflow of Atlantic Water to the Arctic Ocean is a crucial determinant for the future trajectory of this ocean basin with regard to warming, loss of sea ice, and ocean acidification. Yet many details of the fate and circulation of these waters within the Arctic remain unclear. Here, we use the two long-lived anthropogenic radionuclides 129I and 236U together with two age models to constrain the pathways and circulation times of Atlantic Water in the surface (10-35 m depth) and in the mid-depth Atlantic layer (250-800 m depth). We thereby benefit from the unique time-dependent tagging of Atlantic Water by these two isotopes. In the surface layer, a binary mixing model yields tracer ages of Atlantic Water between 9-16 years in the Amundsen Basin, 12-17 years in the Fram Strait (East Greenland Current), and up to 20 years in the Canada Basin, reflecting the pathways of Atlantic Water through the Arctic and their exiting through the Fram Strait. In the mid-depth Atlantic layer (250-800 m), the transit time distribution (TTD) model yields mean ages in the central Arctic ranging between 15 and 55 years, while the mode ages representing the most probable ages of the TTD range between 3 and 30 years. The estimated mean ages are overall in good agreement with previous studies using artificial radionuclides or ventilation tracers. Although we find the overall flow to be dominated by advection, the shift in the mode age towards a younger age compared to the mean age also reflects the presence of a substantial amount of lateral mixing. For applications interested in how fast signals are transported into the Arctic's interior, the mode age appears to be a suitable measure. The short mode ages obtained in this study suggest that changes in the properties of Atlantic Water will quickly spread through the Arctic Ocean and can lead to relatively rapid changes throughout the upper water column in future years. © Author(s) 2021.
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published
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Journal / series
Volume
17 (1)
Pages / Article No.
111 - 129
Publisher
Copernicus
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Date collected
Date created
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Organisational unit
09755 - Casacuberta Arola, Núria / Casacuberta Arola, Núria
03731 - Gruber, Nicolas / Gruber, Nicolas
08619 - Labor für Ionenstrahlphysik (LIP) / Laboratory of Ion Beam Physics (LIP)
Notes
Funding
154805 - A new multitracer approach in Oceanography: combining U-236 with conventional anthropogenic radionuclides in the Arctic and Atlantic Oceans (SNF)
820989 - Our common future ocean – quantifying coupled cycles of carbon, oxygen, and nutrients for determining and achieving safe operating spaces with respect to tipping points (EC)
820989 - Our common future ocean – quantifying coupled cycles of carbon, oxygen, and nutrients for determining and achieving safe operating spaces with respect to tipping points (EC)
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