The Canary Intermediate Poleward Undercurrent: Not Another Poleward Undercurrent in an Eastern Boundary Upwelling System

• Main Authors: Vélez-Belchí, Pedro, Caínzos, V., Romero, E., Casanova-Masjoan, M., Arumí-Planas, C., Santana-Toscano, D., González-Santana, Juan Alberto, Pérez-Hernández, M. D., Hernández-Guerra, A.
• Other Authors: Ministerio de Economía y Competitividad (España), Agencia Canaria de Investigación, Innovación y Sociedad de la Información, European Commission, Universidad de Las Palmas de Gran Canaria, University of Hawaii at Manoa, National Oceanic and Atmospheric Administration (US)
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Meteorological Society 2021
• Subjects: Boundary currents; Continental shelf/slope; Meridional overturning circulation; North Atlantic Ocean; Ocean circulation; Upwelling/downwelling; Antarctic; The Antarctic; Antarc*; North Atlantic
• Online Access: http://hdl.handle.net/10261/346824; https://doi.org/10.1175/JPO-D-20-0130.1; https://doi.org/10.13039/501100007757; https://doi.org/10.13039/501100003329; https://doi.org/10.13039/501100000780; https://doi.org/10.13039/501100006368; https://doi.org/10.13039/100000192; https://api.elsevier.com/content/abstract/scopus_id/85151422584

Poleward undercurrents are well-known features in eastern boundary upwelling systems. In the California Current upwelling system, the California poleward undercurrent has been widely studied, and it has been demonstrated that it transports nutrients from the equatorial waters to the northern limit of the subtropical gyre. However, in the Canary Current upwelling system, the Canary intermediate poleward undercurrent (CiPU) has not been properly characterized, despite recent studies arguing that the dynamics of the eastern Atlantic Ocean play an important role in the Atlantic meridional overturning circulation, specifically on its seasonal cycle. Here, we use trajectories of Argo floats and model simulations to characterize the CiPU, including its seasonal variability and its driving mechanism. The Argo observations show that the CiPU flows from 26°N, near Cape Bojador, to approximately 45°N, near Cape Finisterre and flows deeper than any poleward undercurrent in other eastern boundaries, with a core at a mean depth of around 1000 dbar. Model simulations manifest that the CiPU is driven by the meridional alongshore pressure gradient due to general ocean circulation and, contrary to what is observed in the other eastern boundaries, is still present at 1000 dbar as a result of the pressure gradient between the Antarctic Intermediate Waters in the south and Mediterranean Outflow waters in the north. The high seasonal variability of the CiPU, with its maximum strength in autumn and minimum in spring, is due to the poleward extension of AAIW, forced by Ekman pumping in the tropics. This study has been carried out as part of the RAPROCAN Project, the Canary Islands component of the core observational program of the Instituto Español de Oceanografía; the SAGA project (RTI2018-100844-B-C32), funded by the Ministerio de Economía y Competividad; the EA-RISE (Euro-Argo Research Infrastructure Sustainability and Enhancement) project, funded by European Union’s Horizon 2020 research and innovation program under Grant ...