Fronts in the Southern Indian Ocean as inferred from satellite sea surface temperature data

Kostianoy, Andrey G.; Ginzburg, A. I.; Frankignoulle, Michel; Delille, Bruno

doi:10.1016/j.jmarsys.2003.09.004

Cited by 100 publications

(77 citation statements)

References 33 publications

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“…Major oceanographic fronts are indicated after Lutjeharms and Valentine [1984], Belkin and Gordon [1996], and Kostianoy et al [2004]. The grey rectangle represents a large patch enriched in chlorophyll pigment during the present austral summer conditions [Machu et al, 1999], and the dotted line indicates the variability of the Agulhas Return Current over the Agulhas Plateau [after Boebel et al, 2003].…”

Section: Methodsmentioning

confidence: 99%

“…Off the southern tip of South of Africa it undergoes a retroflection returning back into the South Indian Ocean and flows east as the Agulhas Return Current (ARC). The regional pattern of the ARC is locked to the submarine morphologic high of the Agulhas Plateau that steers the ARC into a quasi-stationary northward meander (Figure 1) seen in hydrographic, kinematic and dynamical data [Harris, 1970;Lutjeharms and van Ballegooyen, 1984;Gordon et al, 1987;Lutjeharms and Ansorge, 2001;Boebel et al, 2003;Kostianoy et al, 2004]. In the retroflection area, warm water eddies, so-called Agulhas rings spin off from the main current ( Figure 1) and drift westward into the South Atlantic Ocean contributing to the interbasin exchange of heat and salt between the Indian and the South Atlantic Ocean [Gordon, , 2003Lutjeharms, 1996].…”

Section: Modern Hydrographymentioning

confidence: 99%

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Paleoceanography of the southern Agulhas Plateau during the last 150 ka: Inferences from benthic foraminiferal assemblages and multispecies epifaunal carbon isotopes

et al. 2007

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[1] Benthic foraminiferal assemblages and the carbon isotope composition of the epifaunal benthic foraminifera Epistominella exigua and Fontbotia wuellerstorfi have been investigated along core MD02-2589 located at the southern Agulhas Plateau (41°26.03 0 S, 25°15.30 0 E, 2660 m water depth). This study aims to evaluate changes in the benthic paleoenvironment and its influence on benthic d 13 C with a notable focus on E. exigua, a species associated with phytodetritus deposits and poorly studied in isotope paleoceanographic reconstructions. The benthic foraminiferal assemblages (>63 mm) show large fluctuations in species composition suggesting significant changes in the pattern of ocean surface productivity conceivably related to migrations of the Subtropical Convergence (STC) and Subantarctic Front (SAF). Low to moderate seasonality and relatively higher food supply to the seafloor are indicated during glacial marine isotope stages (MIS) 6, 4, and 2 and during MIS 3, probably associated with the northward migration of the SAF and confluence with the more stationary STC above the southern flank of the Agulhas Plateau. The lowest organic carbon supply to the seafloor is indicated from late MIS 5b to MIS 4 as a consequence of increased influence of the Agulhas Front (AF) and/or weakening of the influence of the STC over the region. Episodic delivery of fresh organic matter, similar to modern conditions at the core location, is indicated during MIS 5c-MIS 5e and at Termination I. Comparison of this paleoenvironmental information with the paired d 13 C records of E. exigua and F. wuellerstorfi suggests that organic carbon offsets d 13 C of E. exigua from ambient bottom water d 13 C DIC , while its d 13 C amplitude, on glacial-interglacial timescales, does not seem affected by changes of organic carbon supply to the seafloor. This suggests that this species calcifies preferentially during the short time span of the year when productivity peaks and phytodetritus is delivered to the seafloor. Therefore E. exigua, while offset from d 13 C DIC , potentially more faithfully records the amplitude of ambient bottom water d 13 C DIC changes than F. wuellerstorfi, notably in settings such as the Southern Ocean that experienced substantial changes through time in the organic carbon supply to the seafloor.Citation: Diz, P., I. R. Hall, R. Zahn, and E. G. Molyneux (2007), Paleoceanography of the southern Agulhas Plateau during the last 150 ka: Inferences from benthic foraminiferal assemblages and multispecies epifaunal carbon isotopes, Paleoceanography, 22, PA4218,

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Section: Methodsmentioning

confidence: 99%

Section: Modern Hydrographymentioning

confidence: 99%

Paleoceanography of the southern Agulhas Plateau during the last 150 ka: Inferences from benthic foraminiferal assemblages and multispecies epifaunal carbon isotopes

et al. 2007

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“…2E and F) and water temperature profiles (Fig. 3) to characterize the hydrography of the study area (Park et al, 1993;Moore et al, 1999;Park et al, 2002;Kostianoy et al, 2004).…”

Section: Oceanographic Data Setsmentioning

confidence: 99%

“…We used Pathfinder SST data from the advanced very high resolution radiometer (AVHRR), with a spatial resolution of 9 km (Reynolds and Smith, 1994), which are available from the Jet Propulsion Laboratory (JPL) (http://podaac.jpl.nasa.gov/pub/ sea_surface_temperature/avhrr/pathfinder/datav4.1/), have been used previously to map SST fronts in the study area (Park et al, 2002;Kostianoy et al, 2004). Because we encountered a wide range of wind speeds (3.7-91.1 km h -1 ) during our cruise (Fig.…”

Section: Article In Pressmentioning

confidence: 99%

“…A major oceanographic feature in this region is the subtropical convergence (STC), a broad ($100 km) frontal region separating warm and salty subtropical waters to the north, from cold and fresh sub-Antarctic waters to the south (Park et al, 1993(Park et al, , 2002Park and Gambe´roni, 1995;Kostianoy et al, 2004). Between 301S and 451S, surface waters are brought together by the prevalent wind patterns, thereby creating a zone of enhanced surface gradients (Lutjeharms, 1985;Furuya et al, 1986;Park and Gambe´roni, 1995;Rio and Herna´n-dez, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Community structure across a large-scale ocean productivity gradient: Marine bird assemblages of the Southern Indian Ocean

Hyrenbach

Veit

Weimerskirch

et al. 2007

Deep Sea Research Part I: Oceanographic Research Papers

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International audienceOur objective was to understand how marine birds respond to oceanographic variability across the Southern Indian Ocean using data collected during an 16-day cruise (4-21 January 2003). We quantified concurrent water mass distributions, ocean productivity patterns, and seabird distributions across a heterogeneous pelagic ecosystem from subtropical to sub-Antarctic waters. We surveyed 5155km and sighted 15,606 birds from 51 species, and used these data to investigate how seabirds respond to spatial variability in the structure and productivity of the ocean. We addressed two spatial scales: the structure of seabird communities across macro-mega scale (1000 s km) biogeographic domains, and their coarse-scale (10 s km) aggregation at hydrographic and bathymetric gradients. Both seabird density and species composition changed with latitudinal and onshore-offshore gradients in depth, water temperature, and chlorophyll-a concentration. The average seabird density increased across the subtropical convergence (STC) from 2.4 birdskm² in subtropical waters to 23.8 birdskm² in sub-Antarctic waters. The composition of the avifauna also differed across biogeographic domains. Prions (Pachyptila spp.) accounted for 57% of all sub-Antarctic birds, wedge-tailed shearwaters (Puffinus pacificus) accounted for 46% of all subtropical birds, and Indian Ocean yellow-nosed albatross (Thallasarche carteri) accounted for 32% of all birds in the STC. While surface feeders were the most abundant foraging guild across the study area, divers were disproportionately more numerous in the sub-Antarctic domain, and plungers were disproportionately more abundant in subtropical waters. Seabird densities were also higher within shallow shelf-slope regions, especially in sub-Antarctic waters, where large numbers of breeding seabirds concentrated. However, we did not find elevated seabird densities along the STC, suggesting that this broad frontal region is not a site of enhanced aggregation

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Southern Ocean jets and how to find them: Improving and comparing common jet detection methods

Chapman

2014

JGR Oceans

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This study undertakes a detailed comparison of different methods used for detecting and tracking oceanic jets in the Southern Ocean. The methods under consideration are the gradient thresholding method, the probability density function (PDF) method, and the contour method. Some weaknesses of the gradient thresholding method are discussed and an enhancement (the WHOSE method), based on techniques from signal processing, is proposed. The WHOSE method is then compared to the other three methods. Quantitative comparison is undertaken using synthetic sea-surface height fields. The WHOSE method and the contour method are found to perform well even in the presence of a strong eddy field. In contrast, the standard gradient thresholding and PDF methods only perform well in high signal-to-noise ratio situations. The WHOSE, PDF, and the contour methods are then applied to data from the eddy-resolving Ocean General Circulation Model for the Earth Simulator. While the three methods are in broad agreement on the location of the main ACC jets, the nature of the jet fields they produce differ. In particular, the WHOSE method reveals a fine-scale jet field with complex braiding behavior. It is argued that this fine-scale jet field may affect the calculation of eddy diffusivities. Finally, recommendations based on this study are made. The WHOSE and gradient thresholding methods are more suitable for the study of jets as localized strong currents, useful for studies of tracer fluxes. The contour and PDF methods are recommended for studies linking jets to hydrographic fronts.

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Fronts in the Southern Indian Ocean as inferred from satellite sea surface temperature data

Cited by 100 publications

References 33 publications

Paleoceanography of the southern Agulhas Plateau during the last 150 ka: Inferences from benthic foraminiferal assemblages and multispecies epifaunal carbon isotopes

Paleoceanography of the southern Agulhas Plateau during the last 150 ka: Inferences from benthic foraminiferal assemblages and multispecies epifaunal carbon isotopes

Community structure across a large-scale ocean productivity gradient: Marine bird assemblages of the Southern Indian Ocean

Southern Ocean jets and how to find them: Improving and comparing common jet detection methods

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