Dynamics of deep recirculation cells offshore of the deep western boundary current in the subtropical North Atlantic (15°-30°N)

Tiago Carrilho Biló, William E. Johns, Jian Zhao

Research output: Contribution to journalArticlepeer-review

Abstract

The dynamics of the deep recirculation offshore of the deep western boundary current(DWBC) between 15° and 30°N within the upper North Atlantic Deep Water layer (1000 ≤ z ≤ 3000 m) is investigated with two different eddyresolving numerical simulations. Despite some differences in the recirculation cells, our assessment of the modeled deep isopycnal circulation patterns (36.77 ≤ σ2 ≤ 37.06 kgm-3) shows that both simulations predict the DWBC flowing southward along the continental slope, while the so-called Abaco Gyre and two additional cyclonic cells recirculate waters northward in the interior. These cells are a few degrees wide, located along the DWBCpath, and characterized by potential vorticity (PV) changes occurring along their mean streamlines. The analysis of the mean PV budget reveals that these changes result from the action of eddy forcing that tends to erode the PV horizontal gradients. The lack of a major upperocean boundary current within the study region, and the fact that the strongest eddy forcing is constrained within a few hundreds of kilometers of the western boundary, suggest that the DWBC is the primary source of eddy forcing. Finally, the eddies responsible for forcing the recirculation have dominant time scales between 100 and 300 days, which correspond to the primary observed variability scales of the DWBC transport at 26.5°N.

Original languageEnglish (US)
Pages (from-to)131-145
Number of pages15
JournalJournal of Physical Oceanography
Volume51
Issue number1
DOIs
StatePublished - Jan 2021

Keywords

  • Abyssal circulation
  • Dynamics
  • Mesoscale processes
  • Ocean circulation
  • Ocean dynamics
  • Potential vorticity

ASJC Scopus subject areas

  • Oceanography

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