The Malvinas Current at the Confluence With the Brazil Current: Inferences From 25 Years of Mercator Ocean Reanalysis

Abstract

Twenty‐five years of high‐resolution (1/12°) ocean reanalysis are used to examine the Confluence of the Malvinas Current (MC) with the Brazil Current (BC) from synoptic to interannual time scales. The model transports of the MC (38.0 Sv ± 7.4 Sv 57 at 41°S) and the BC (23.0 Sv ± 11 Sv at 36°S) agree with observations. The model shows the branching of the MC near the Confluence with an offshore branch returning south and an inner branch sinking below the BC and managing to continue northward along the continental slope. Northward velocities associated with the subsurface inner branch peak at 40 cm/s at 36°S at 700‐m depth. The model documents the migrations of the Subantarctic (SAF) and Subtropical Fronts (STF) at the Confluence. The SAF and STF positions vary over a large range at synoptic (800 km) and interannual scale (300 and 200 km, respectively) compared to the rather small seasonal migrations of the STF (150 km) and SAF (50 km). While trends in the MC are small over the 25 years of the reanalysis, the BC becomes more intense (12.5 cm/s), saltier (0.37 psu), and warmer (2.5°C) in the upper 1,000 m. These trends are accompanied with a southward displacement of the STF and the SAF of 150 and 50 km.

Subsurface Ocean Warming Hotspots and Potential Impacts on Marine Species: The Southwest South Atlantic Ocean Case Study

“…The resilience capacity of the benthic communities dependent on SBF productivity is also a key issue which requires further investigation. Stronger warming trends in subsurface waters reported by our study (Figure 8) are consistent with observations from Artana et al (2019), who report a long-term trend of BC intensification and warming at 36 • S in the upper 1,000 m (see their Figures 13A,C). The southward displacement of the tropical BC waters and the induced changes in the advection of BC deeper waters are suggested to induce such changes in the warming trend of deeper waters (their Figures 2, 13).…”

“…The model assimilates observations with a 7−day assimilation cycle (Lellouche et al, 2013), including along−track satellite altimetry data from CMEMS (Pujol et al, 2016), satellite SST from NOAA, sea−ice concentration, and in situ temperature and salinity vertical profiles from the latest CORA in situ databases (Szekeley et al, 2016). GLORYS12 provides a realistic representation of the general circulation of the SWAO and the location of the BMC (Artana et al, 2018(Artana et al, , 2019.…”

Anatomy of Subinertial Waves Along the Patagonian Shelf Break in a 1/12° Global Operational Model

“…Extreme transport maxima in the MC at 41°S were related with cyclonic eddies detached from the PF that propagate northward along the 400‐m isobath (Artana et al., 2018a). The significant energetic peaks in a 30–110‐day period band found in the MC transport at 41°S and in the velocity time series associated with the subducted inner branch of the MC at 37°S (Artana et al., 2019) could be associated with TW. Theoretical works also suggested that TW could affect the position of the encounter of the Brazil and Malvinas Current (Lebedev & Nof, 1997).…”

“…High‐resolution ocean models (1/12°) that assimilate in situ observations and along‐track satellite altimetry, such as the Mercator Ocean physical reanalysis at 1/12°, could provide some insights on TW propagating along the Patagonian shelf break. Previous works have assessed the performance of this reanalysis in the MC system (Artana et al., 2018a, 2019). Here, we further evaluate the spectral content of the reanalysis SLAs and velocities on the slope compared to observations.…”

“…MC system (Artana et al, 2018a(Artana et al, , 2019. Here, we further evaluate the spectral content of the reanalysis SLAs and velocities on the slope compared to observations.…”