Dynamics and Temporal Variability of the North Atlantic Current in the Iceland Basin (2014–2022).
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| Title: | Dynamics and Temporal Variability of the North Atlantic Current in the Iceland Basin (2014–2022). |
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| Authors: | Dotto, Tiago S.1 (AUTHOR) tiago.dotto@noc.ac.uk, Holliday, N. Penny1 (AUTHOR), Fraser, Neil2 (AUTHOR), Moat, Ben1 (AUTHOR), Firing, Yvonne1 (AUTHOR), Burmeister, Kristin2 (AUTHOR), Rayner, Darren1 (AUTHOR), Cunningham, Stuart2 (AUTHOR), Worthington, Emma3 (AUTHOR), Johns, William E.3 (AUTHOR) |
| Source: | Journal of Geophysical Research. Oceans. Jun2025, Vol. 130 Issue 6, p1-20. 20p. |
| Subject Terms: | *Atlantic meridional overturning circulation, *Ocean currents, Enthalpy, Gulf Stream, Zonal winds |
| Abstract: | The North Atlantic Current (NAC) is a major source of heat toward the subpolar gyre and northern seas. However, its variability and drivers are not well understood. Here, we evaluated 8 years of continuous daily measurements as part of the international program Overturning in the Subpolar North Atlantic Program to investigate the NAC in the Iceland Basin. We found that the NAC volume and freshwater anomaly transport and heat content (HC) were highly variable with significant variability at timescales of 16–120 days to annual. Intraseasonal to short interannual variability was associated with mesoscale and intermittent mesoscale features abundant in the region. Composites analysis revealed that strong NAC periods were associated with less eddy kinetic energy in the Iceland Basin, which was consistent with the presence of frontal‐like structures instead of eddy‐like structures. On longer timescales, the westward migration of the eastern boundary of the subpolar North Atlantic (SPNA) gyre favors a stronger NAC volume transport and HC in the region. Stronger zonal wind stress triggers a fast response that piles water up between the SPNA and subtropical gyres, which increases the sea surface height gradient and drives the acceleration of the NAC. The strengthening of the NAC increases the heat and salt transport northward. During our study period, both heat and salt increased across the moorings. These observations are important for understanding the heat and freshwater variability in the SPNA, which ultimately impacts the Atlantic meridional overturning circulation. Plain Language Summary: The Atlantic meridional overturning circulation (AMOC) is a complex system of ocean currents that bring heat poleward and cold/fresh waters equatorward. The North Atlantic Current (NAC), derived from the Gulf Stream, is a major heat source toward the subpolar gyre and northern seas. Here, we evaluated 8 years of daily data measured as part of the international program Overturning in the Subpolar North Atlantic Program. We found that the NAC was highly variable in the Iceland Basin with variability at timescales of 16–120 days to annual. The shorter timescales were associated with eddies propagating with the NAC. Strong NAC was related to periods of strong zonal gradient across the current, less eddy kinetic energy, and with a westward excursion of the eastern boundary of the subpolar North Atlantic gyre. This opened space for warmer water to access the northern environments, such as after 2017. Over 2014–2022, we observed warming and salinification of the upper ocean, which might be a recovery of a period of large freshening in 2015. Our findings are important in understanding the variability of heat that is imported into the subpolar North Atlantic and is modified within the gyre and exported within the AMOC's lower limb. Key Points: The North Atlantic Current (NAC) volume transport variability was strong at 16–120‐day periods associated with the mesoscale activity in the Iceland BasinHigh volume transport coincided with the subpolar North Atlantic gyre eastern boundary's westward migration and reduced mesoscale activityNAC volume transport and heat content increased between 2014 and 2022, which can be propagated into the Atlantic meridional overturning circulation deep branch on decadal timescales [ABSTRACT FROM AUTHOR] |
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| Database: | GreenFILE |
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