Red Sea Intermediate Water at the Agulhas Current termination

Roman, Raymond; Lütjeharms, J. R. E.

doi:10.1016/j.dsr.2007.04.009

Cited by 17 publications

(11 citation statements)

References 34 publications

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“…These few unusually saline stations in the south suggest a mixing of Antarctic Intermediate and Red Sea Intermediate Water masses and reflect the influence of the anti‐cyclonic eddy in transporting RSIW southwards in an intermittent fashion. This agrees with recent findings by Roman and Lutjeharms [2007, 2009]. Those profiles extending into the Deep and Bottom waters tend to merge near a salinity of 34.8, and show little meridional or along‐section variation.…”

Section: Resultssupporting

confidence: 92%

“…Previous studies have shown that contributions from the Mozambique Channel significantly influence water mass properties in the Agulhas Current [e.g., DiMarco et al , 2002; Roman and Lutjeharms , 2009]. It has also been demonstrated that at least some of these anomalous water signals remain evident as far downstream as Agulhas Rings [ Roman and Lutjeharms , 2007] and therefore contribute to the flux into the South Atlantic. However, since the majority of Mozambique eddies move poleward outside the Agulhas Current proper [ Schouten et al , 2003], and therefore are not absorbed into the Agulhas Current proper, one can currently only speculate on the quantitative contribution they may make to heat and salt flux into the Agulhas Current and hence into the South Atlantic Ocean.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, the eddy was depleted oxygen. These strong anomalies suggest that the Mozambique Channel eddies may influence the water mass characteristics of the Agulhas Current [e.g., Roman and Lutjeharms , 2009] into which they may partially and intermittently feed, and perhaps ultimately the physical and chemical properties of the South Atlantic basin via Agulhas leakage [e.g., Roman and Lutjeharms , 2007].…”

Section: Discussionmentioning

confidence: 99%

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Observed characteristics of Mozambique Channel eddies

et al. 2010

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[1] The flow in the Mozambique Channel is dominated by large, southward propagating, anti-cyclonic eddies, as opposed to a steady western boundary current. These Mozambique Channel eddies feed their waters into the Agulhas Current system, where they are thought to have a significant influence on the formation of the Natal Pulse and Agulhas Ring shedding. Here we use in situ hydrographic and nutrient data, together with satellite altimetry and surface velocity profilers to provide a detailed characterization of the Mozambique Channel eddies. Two warm eddies in the Channel at 20°S and 24°S had diameters of over 200 km. They rotated anti-cyclonically with a tangential velocity of over 0.5 m.s . Vertical sections show that the eddies reached to the bottom of the water column. Relative to the surrounding waters, the features were warm and saline. The total heat and salt anomalies for the southernmost eddy were computed relative to a reference station close by. At 24°S the total anomalies were 1.3 × 10 20 J and 6.9 × 10 12 kg, respectively, being on par with Agulhas rings. Mozambique Channel eddies thus have the potential to form a major contribution to the southward eddy heat flux in the Agulhas Current system. The feature also had positive nutrient and negative oxygen anomalies. The large magnitude of the water mass anomalies within the eddy suggests that interannual variability in Mozambique Channel eddy numbers would have a significant impact on downstream water mass characteristics.

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Section: Resultssupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Observed characteristics of Mozambique Channel eddies

et al. 2010

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“…The intense evaporation drives the basin-scale vertical overturning circulation and contributes to the formation of the Red Sea Overflow Water (RSOW; Bower & Farrar, 2015;Eshel & Naik, 1997;Papadopoulos et al, 2015;Sofianos & Johns, 2003Yao, Hoteit, Pratt, Bower, Zhai, et al, 2014;. This salty water mass escapes to the Indian Ocean, where it can be traced at intermediate depths as far as the Agulhas Current and the Agulhas Return Current at about 40 • S (Beal et al, 2000;Roman & Lutjeharms, 2007You, 1998). The intense evaporation is also an important source of moisture for the arid Middle-East, influencing the regional hydrological cycle and the precipitation over the adjacent countries (Zolina et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Evaporative Implications of Dry‐Air Outbreaks Over the Northern Red Sea

2019

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We investigate the impacts of westward wind events on the Red Sea evaporation using the 35‐year second Modern‐Era Retrospective analysis for Research and Applications reanalysis and a 2‐year‐long record of in situ observations from a heavily instrumented air‐sea interaction mooring. These events are common during boreal winter, and their effects are similar to cold‐air outbreaks that occur in midpolar and subpolar latitudes. They cause extreme heat loss from the sea, which is dominated by latent heat fluxes. Different from cold‐air outbreaks, the intensified heat loss is due to the low relative humidity as we show through latent heat flux decomposition. Rainfall is negligible during these events, and we refer to them as dry‐air outbreaks. We also investigate the general atmospheric circulation pattern that favors their occurrence, which is associated with an intensified Arabian High at the north‐central portion of the Arabian Peninsula—a feature that seems to be an extension of the Siberian High. The analyses reveal that the westward winds over the northern Red Sea and the winter Shamal winds in the Persian Gulf are very likely to be part of the same subsynoptic‐scale feature. The second Modern‐Era Retrospective analysis for Research and Applications reanalysis indicates that the occurrence of westward wind events over the northern Red Sea has grown from 1980 to 2015, especially the frequency of large‐scale events, the cause of which is to be investigated. We hypothesize that dry‐air outbreaks may induce surface water mass transformation in the surface Red Sea Eastern Boundary Current and could represent a significant process for the oceanic thermohaline‐driven overturning circulation.

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“…However, core speeds of 15 cm s 21 are observed, while the simulation shows speeds of less than 5 cm s 21 . Figure (Roman and Lutjeharms 2007), and a freshening of NADW within the undercurrent from south to north along s 1 5 32.45. The cutoff of the core of NADW toward the north is also clear here, as we saw in Fig.…”

mentioning

confidence: 99%

Variability and Coherence of the Agulhas Undercurrent in a High-Resolution Ocean General Circulation Model

Biastoch¹,

Beal²,

Lütjeharms

et al. 2009

Journal of Physical Oceanography

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The Agulhas Current system has been analyzed in a nested high-resolution ocean model and compared to observations. The model shows good performance in the western boundary current structure and the transports off the South African coast. This includes the simulation of the northward-flowing Agulhas Undercurrent. It is demonstrated that fluctuations of the Agulhas Current and Undercurrent around 50-70 days are due to Natal pulses and Mozambique eddies propagating downstream. A sensitivity experiment that excludes those upstream perturbations significantly reduces the variability as well as the mean transport of the undercurrent. Although the model simulates undercurrents in the Mozambique Channel and east of Madagascar, there is no direct connection between those and the Agulhas Undercurrent. Virtual float releases demonstrate that topography is effectively blocking the flow toward the north.

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Red Sea Intermediate Water at the Agulhas Current termination

Cited by 17 publications

References 34 publications

Observed characteristics of Mozambique Channel eddies

Observed characteristics of Mozambique Channel eddies

Evaporative Implications of Dry‐Air Outbreaks Over the Northern Red Sea

Variability and Coherence of the Agulhas Undercurrent in a High-Resolution Ocean General Circulation Model

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