4.7 Article

Water Mass Transports and Pathways in the North Brazil-Equatorial Undercurrent Retroflection

期刊

出版社

AMER GEOPHYSICAL UNION
DOI: 10.1029/2021JC018150

关键词

Lagrangian transports; western boundary current; Tropical Atlantic

资金

  1. Spanish Government through project SAGA (Ministerio de Ciencia, Innovacion y Universidades) [RTI2018-100844-B-C33]
  2. Spanish Government through a FPI contract (Ministerio de Economia y Competitividad) [BES-2015-071314]
  3. European Union [797236]
  4. Spanish government through a Juan de la Cierva Incorporation grant
  5. Spanish Government through the Severo Ochoa Center of Excellence [CEX2019-000928-S]
  6. Marie Curie Actions (MSCA) [797236] Funding Source: Marie Curie Actions (MSCA)

向作者/读者索取更多资源

The equatorial retroflection of the North Brazil Current and its posterior tropical recirculation play a major role in regulating the Atlantic Meridional Overturning Circulation. This study explores the recirculation pathways and transport variability using cruise data and reanalysis time series. The results show pronounced seasonality in the equatorial and tropical waters, and an enhanced contribution from the South Atlantic tropical waters during 2008-2016 compared to 1997-2007.
The equatorial retroflection of the North Brazil Current (NBC) into the Equatorial Undercurrent (EUC) and its posterior tropical recirculation is a major regulator for the returning limb of the Atlantic Meridional Overturning Circulation. Indeed, most surface and thermocline NBC waters retroflect at the equator all the way into the central and eastern Atlantic Ocean, before they recirculate back through the tropics to the western boundary. Here, we use cruise data in the western equatorial Atlantic during April 2010 and reanalysis time series for the equatorial and tropical waters in both hemispheres in order to explore the recirculation pathways and transport variability. During the 1998-2016 period, the annual-mean EUC transports 15.1 +/- 1.3 Sv at 32 degrees W, with 2.8 +/- 0.4 Sv from the North Atlantic and 11.4 +/- 1.3 Sv from the South Atlantic. At 32 degrees W most of the total EUC transport comes from the western boundary retroflection south of 3 degrees N (7.2 +/- 0.9 Sv), a substantial fraction retroflects north of 3 degrees N (5.6 +/- 0.4 Sv), and the remaining flow (2.3 Sv) joins through the interior basin the South Atlantic subtropical waters feed the EUC at all thermocline depths while the North Atlantic and South Atlantic tropical waters do so at the surface and upper-thermocline levels. The EUC transport at 32 degrees W has a pronounced seasonality, with spring and fall maxima and a range of 8.8 Sv. The 18 yr of reanalysis data shows a weak yet significant correlation with an Atlantic Nino index, and also suggests an enhanced contribution from the South Atlantic tropical waters during 2008-2016 as compared with 1997-2007.

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