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

Vallès‐Casanova, Ignasi; Fraile-Nuez, E.; Martín‐Rey, Marta; Sebille, Erik van; Cabré, Anna; Abelló, Anna Olivé; Pelegrí, Josep Lluís

doi:10.1029/2021jc018150

Cited by 5 publications

(6 citation statements)

References 94 publications

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“…It is common practice in many Lagrangian studies of advective timescales (e.g., Drake et al., 2018; Tamsitt et al., 2021), and pathways (e.g., Blanke et al., 1999; Fröhle et al., 2022; Rühs et al., 2022; Schmidt et al., 2021; Tamsitt et al., 2017; Vallès‐Casanova et al., 2022; van Sebille et al., 2014), to tag particles with a volume transport (van Sebille et al., 2018). Indeed Lagrangian particle experiments conducted with Parcels have previously been used to estimate volume transports, even when the integration scheme is not strictly volume conserving (Fröhle et al., 2022; Rühs et al., 2022; Schmidt et al., 2021; Vallès‐Casanova et al., 2022), because the trajectories calculated by explicit time‐stepping in the absence of diffusion are similar to trajectories calculated by analytical methods (van Sebille et al., 2018). We follow this convention in our analyses and weight each particle in our simulation with the transport through the corresponding model grid cell in which it was released.…”

Section: Methodsmentioning

confidence: 99%

Pathways and Timescales of Connectivity Around the Antarctic Continental Shelf

et al. 2023

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The Antarctic Slope Current (ASC) and Antarctic Coastal Current advect heat, freshwater, nutrients, and biological organisms westward around the Antarctic margin, providing a connective link between different sectors of the continental shelf. Yet the strength and pathways of connectivity around the continent, and the timescales of advection, remain poorly understood. We use daily velocity fields from a global high‐resolution ocean‐sea ice model, combined with Lagrangian particle tracking, to shed light on these timescales and improve our understanding of circumpolar connectivity around Antarctica. Virtual particles were released along vertical transects over the continental shelf every 5 days for a year and were tracked forward in time for 21 years. Analysis of the resulting particle trajectories highlights that the West Antarctic sector has widespread connectivity with all regions of the Antarctic shelf. Advection around the continent is typically rapid with peak transit times of 1–5 years for particles to travel 90° of longitude downstream. The ASC plays a key role in driving connectivity in East Antarctica and the Weddell Sea, while the Coastal Current controls connectivity in West Antarctica, the eastern Antarctic Peninsula, and along the continental shelf east of Prydz Bay. Connectivity around the shelf is impeded in two main locations, namely, the tip of the Antarctic Peninsula and Cape Adare in the Ross Sea, where significant export of water from the continental shelf is found. These findings help to understand the locations and timescales over which anomalies, such as meltwater from the Antarctic Ice Sheet, can be redistributed downstream.

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Section: Methodsmentioning

confidence: 99%

Pathways and Timescales of Connectivity Around the Antarctic Continental Shelf

et al. 2023

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“…Even though we focus on subduction rates of water within the EUC density range, not all of this water is actually feeding into the EUC. As the time scale for subducted water to reach the EUC is in the range of several years (Vallès‐Casanova et al., 2022), we can assume that the instantaneous EUC transport changes are independent of the changes of the total annual subduction rates. The underlying cause for both strengthening of the EUC transport as well as the subduction rates are the intensified trade winds.…”

Section: Resultsmentioning

confidence: 99%

“…North of the equator, the NBC retroflects to the southeast, feeding into the eastward flowing NECC/NEUC at around 5°N and the EUC at the equator (Hazeleger et al., 2003; Schott et al., 1998). A small contribution to the NBC retroflection was suggested to originate from the North Atlantic via the NEC (Bourlès et al., 1999; Vallès‐Casanova et al., 2022) which forms the western boundary pathway of the Northern Hemisphere STC, described above. A third pathway of subducted water, that does not participate in the STC, is the recirculation pathway where the water is trapped in the subtropical gyre (pathway (3) in Figure 1) (Liu et al., 1994; McCreary & Lu, 1994; Schott et al., 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Black stippled lines show the three different pathways, gray solid lines denote the mean surface-thermocline circulation field. This schematic is based on the circulation and pathway schemes in Stramma and Schott (1999), Zhang et al (2003), Schott et al (2004), Hahn et al (2017), Tuchen et al (2022b) andVallès-Casanova et al (2022). (Hazeleger et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

“…(Hazeleger et al, 2003). With the NBC retroflection, a part of the thermocline water is supplied into the NECC/ NEUC or may reach the equator to supply the EUC (Figure 1) (Vallès-Casanova et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

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Impact of the North Atlantic Oscillation on the Decadal Variability of the Upper Subtropical‐Tropical Atlantic Ocean

Roch,

Brandt,

Schmidtko

et al. 2024

JGR Oceans

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In the northeastern tropical Atlantic, a region of high potential vorticity (PV) determines the size of the exchange window for the interior thermocline flow of the subtropical cell via its variations in strength and extent. Variability of this PV barrier has the potential to impact the ventilation of the tropical Atlantic on decadal timescales. Here, the impact of the North Atlantic Oscillation (NAO) on the PV barrier related to isopycnals within the thermocline of the subtropical‐tropical Atlantic Ocean is assessed from Argo observations for the time period of 2006–2022. Relative to the negative NAO phase (2009–2010), during the positive NAO phase (2014–2019), the North Atlantic subtropical high and the northeast trades are intensified. Satellite‐derived wind stress curl shows increased upwelling/downwelling on the equatorward/poleward side of the trade wind zone, respectively. In the subtropical‐tropical Atlantic, a symmetric pattern of isopycnal heave is observed: rising isopycnals within 20°N and 20°S and sinking poleward of that. With rising isopycnals, the PV barrier in the northeastern tropical Atlantic becomes stronger. Analyses of geostrophic velocities and the Sverdrup streamfunction show that during the positive NAO phase there are increased equatorward velocities at thermocline level along the western boundary and reduced velocities through the interior as a result of intensified northeast trades and therefore a strengthened PV barrier. Intensified trades lead to enhanced subduction of thermocline waters and, independent of that, to a strengthened Equatorial Undercurrent transport as observed at the mooring site at 0°, 23°W, likely via the pulling effect of the subtropical cells.

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Water masses in the Caribbean Sea and sub-annual variability in the Guajira upwelling region

Parra

Solana²,

Barros

et al. 2023

Ocean Dynamics

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The study of water masses is important as they transport water properties affecting the biosphere and ocean dynamics. In this study, we revisit water masses in the Caribbean Sea using climatology and 11 months of observations at different depths from 3 moorings placed in the Guajira upwelling region, providing some new findings. The Caribbean Surface Water (CSW) seasonal variability is studied at the mixed layer depth. Salinity differences between CSW and the saltier North Atlantic Subtropical Underwater (SUW) determine static stability spatial and temporal variations, with implications for regional ocean dynamics. Besides, we assess the climatologic distribution of water masses below the salinity maximum using the optimum multiparameter analysis and the Thermodynamic Equation of Seawater 2010, defining their source water indices when entering the Caribbean Sea. The SUW, with its core at ~ 150 m depth, occupies 16% of the Caribbean Sea volume, complemented by 38% of Antarctic Intermediate Water, with its core at ~ 700 m depth and North Atlantic Deep Water, which as bottom water occupies 46% of the volume. Hydrographic observations do not differ from climatology, regardless of their large sub-annual variations decreasing with depth. Daily time series of dominant water fractions at different depths correlate at each mooring, indicating a common forcing. Besides, rotated wind stress, which is an indicator of the Guajira upwelling, correlates regularly with water mass fractions down to 700 m depth. However, during strong wind shifts, upwelling seems to affect them down to 1450 m depth.

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

Cited by 5 publications

References 94 publications

Pathways and Timescales of Connectivity Around the Antarctic Continental Shelf

Pathways and Timescales of Connectivity Around the Antarctic Continental Shelf

Impact of the North Atlantic Oscillation on the Decadal Variability of the Upper Subtropical‐Tropical Atlantic Ocean

Water masses in the Caribbean Sea and sub-annual variability in the Guajira upwelling region

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