The East Madagascar Current: Volume Transport and Variability Based on Long-Term Observations

Ponsoni, Leandro; Aguiar‐González, Borja; Ridderinkhof, H.; Maas, Leo R. M.

doi:10.1175/jpo-d-15-0154.1

Cited by 16 publications

(34 citation statements)

References 58 publications

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“…Further south, the poleward flowing SEMC transports −17 Sv (−15 to −20 Sv; Fig. 4b; top panel), which is a lower magnitude than observational estimates of −18 to −30 Sv 38,39,41–43 (Supplementary Table S2). The SEMC transport seasonal timing is generally consistent across the models, with an annual range of 5.4 Sv (Fig.…”

Section: Resultsmentioning

confidence: 79%

Projected slow down of South Indian Ocean circulation

Stellema

Gupta

Taschetto

2019

Sci Rep

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Using an ensemble of 28 climate models, we examine hindcasts and ‘business as usual’ future changes to large-scale South Indian Ocean dynamics. We compare model ensemble seasonal-to-annual volume transports to observations and explore drivers of past and future circulation variability and change. Off the west coast of Australia, models consistently project a weakening of the Leeuwin Current and Undercurrent due to reduced onshore flow and downwelling. The reduced onshore flow is related to changes in the alongshore pressure gradient. While the alongshore pressure gradient change is consistent with the Indonesian Throughflow projected weakening, we found no inter-model relationship between these changes. In the south-western Indian Ocean, the models project a robust weakening of the North East and South East Madagascar Currents, Agulhas Current and transport through the Mozambique Channel. This reduced Indian Ocean western boundary flow is partly associated with a weaker Indonesian Throughflow and overturning circulation, where the latter is related to a decrease in the convergence of deep Southern Ocean waters into the Indian Ocean. In contrast to the weakening of other features, the westward flowing Agulhas Current extension south of Africa is projected to strengthen, which is consistent with an intensification of the Antarctic Circumpolar Current.

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Section: Resultsmentioning

confidence: 79%

Projected slow down of South Indian Ocean circulation

Stellema

Gupta

Taschetto

2019

Sci Rep

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“…This eddy generation site is collocated with the enhanced signal of EAPE near 100 E, shown within the box in Figure 1b. The western box was based on the observations reported by Ponsoni et al (2015Ponsoni et al ( , 2016, which suggest that altimeter-detected eddies drive a significant variability of the Journal of Geophysical Research: Oceans 10.1029/2018JC013828 volume transport carried by the EMC. In accordance with these findings, the western box was located in the open ocean, before interaction with the EMC, so that the properties of the eddies are captured prior to their arrival to the western boundary.…”

Section: Introductionmentioning

confidence: 99%

SIDDIES Corridor: A Major East‐West Pathway of Long‐Lived Surface and Subsurface Eddies Crossing the Subtropical South Indian Ocean

et al. 2018

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South Indian Ocean eddies (SIDDIES), originating from a high evaporation region in the eastern Indian Ocean, are investigated by tracking individual eddies from satellite data and co‐located Argo floats. A subsurface‐eddy identification method, based on its steric dynamic height anomaly, is devised to assign Argo profiles to surface eddies (surfSIDDIES) or subsurface eddies (subSIDDIES). These westward‐propagating, long‐lived features (>3 months) prevail over a preferential latitudinal band, forming a permanent structure linking the eastern to the western Indian Ocean, that we call the 'SIDDIES Corridor’. Key features have been revealed in the mean thermohaline vertical structure of these eddies. Anticyclonic SIDDIES are characterized by positive subsurface salinity anomalies, with subSIDDIES not exhibiting negative surface anomalies, as opposed to surfSIDDIES. Cyclonic subSIDDIES also occur, but their related salinity anomalies are weaker. SubSIDDIES exhibit two cores of different temperature polarities in their surface and subsurface levels. Cyclonic subSIDDIES have their cores at around 150‐200 m depth along the 25.4‐25.8 kg m−3 potential density layer with anticyclonic subSIDDIES having their cores at 250‐300 m along the 26‐26.4 kg m−3 density layer. The SIDDIES corridor acts as a zonal pathway for both eddy‐types to advect water masses and biogeochemical properties across the basin. This study provides a new insight on heat/salt fluxes, showing that 58% (32%) of the total heat eddy‐flux is ascribed to cyclonic (anticyclonic) subSIDDIES, respectively, in the eastern South Indian Ocean. Anticyclonic subSIDDIES have also been found to be the sole high‐saline water eddy‐conveyor toward the western Indian Ocean.

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“…The northward branch, the North Madagascar Current, bifurcates again along the African continent and forms a poleward flow in the Mozambique channel dominated by large anticyclonic rings (Ullgren et al, 2012), with an estimated mean southward transport of 14 Sv (de Ruijter et al, 2002). The southward branch becomes the East Madagascar Current (EMC), transporting 20 Sv southward along the southeast coast of Madagascar until the southern tip of the island (Ponsoni et al, 2016). Both southward flows are feeding the Agulhas Current system, contributing to the global overturning circulation.…”

Section: Introductionmentioning

confidence: 99%

Uncovering a New Current: The Southwest MAdagascar Coastal Current

Ramanantsoa

Penven

Krug

et al. 2018

Geophysical Research Letters

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Cruise data sets, satellite remote sensing observations, and model data analyses are combined to highlight the existence of a coastal surface poleward flow in the southwest of Madagascar: the Southwest MAdagascar Coastal Current (SMACC). The SMACC is a relatively shallow (<300 m) and narrow (<100 km wide) warm and salty coastal surface current, which flows along the south western coast of Madagascar toward the south, opposite to the dominant winds. The warm water surface signature of the SMACC extends from 22°S (upstream) to 26.4°S (downstream). The SMACC exhibits a seasonal variability: more intense in summer and reduced in winter. The average volume transport of its core is about 1.3 Sv with a mean summer maximum of 2.1 Sv. It is forced by a strong cyclonic wind stress curl associated with the bending of the trade winds along the southern tip of Madagascar. The SMACC directly influences the coastal upwelling regions south of Madagascar. Its existence is likely to influence local fisheries and larval transport patterns, as well as the connectivity with the Agulhas Current, affecting the returning branch of the global overturning circulation.

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The East Madagascar Current: Volume Transport and Variability Based on Long-Term Observations

Cited by 16 publications

References 58 publications

Projected slow down of South Indian Ocean circulation

Projected slow down of South Indian Ocean circulation

SIDDIES Corridor: A Major East‐West Pathway of Long‐Lived Surface and Subsurface Eddies Crossing the Subtropical South Indian Ocean

Uncovering a New Current: The Southwest MAdagascar Coastal Current

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