Simulated Lagrangian pathways between the Leeuwin Current System and the upper-ocean circulation of the southeast Indian Ocean

Domingues, Catia M.; Maltrud, Mathew; Wijffels, Susan E.; Church, John A.; Tomczak, Matthias

doi:10.1016/j.dsr2.2006.10.003

Cited by 137 publications

(145 citation statements)

References 71 publications

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“…1b-c; A. Waite, unpublished data). The seasonal acceleration of warm, more saline Leeuwin Current surface water (though still less saline than the STW) in the austral autumn (Domingues et al, 2007) observed in this study is therefore likely to have occurred regionally in the intervening month, subducting the lower salinity EGC layer beneath it (see schematic in Fig. 9).…”

Section: Oceanographic History and Formation Of Ldohn Layersmentioning

confidence: 96%

“…Here, the Leeuwin Current consolidates from several surface pathways, including warm and saline waters coming from the Indonesian Throughflow (Western Pacific) and the tropical Indian Ocean, fresher Indonesian waters transported by the Eastern Gyral Current (EGC) (Domingues et al, 2007), and cooler, more saline waters from the South Indian Ocean (Figs. 1 and 2a-e).…”

Section: Primary Research Voyagementioning

confidence: 99%

“…During the primary cruise in May 2010, we identified several regional water masses and currents occurring in the study region (Domingues et al, 2007;Woo and Pattiaratchi, 2008) including subtropical water (STW; salinity ∼ 35.2) entering from the southwest, Eastern Gyral Current (EGC; salinity ∼ 34.8) waters entering from the west and northwest, and Leeuwin Current/Indonesian Throughflow (LC/ITF; salinity ∼ 35.6) from the north and northeast (Fig. 1a).…”

Section: Primary Research Voyagementioning

confidence: 99%

“…Map of study area showing sampling locations as filled circles and the direction of inflow of the major regional water masses and currents: the Leeuwin Current (LC) waters sourced variously from the Indonesian Throughflow (ITF) and from tropical waters (see Domingues et al, 2007) was used as an indicator of particle concentration (Karageorgis et al, 2008). Chlorophyll a (Parsons et al, 1984), total alkalinity and total dissolved inorganic carbon (DIC) measurements were made on samples from bottles fired at up to 10 depths, with 3-4 samples identified as being specifically within or outside the LDOHN layer.…”

Section: Fig 1 (A)mentioning

confidence: 99%

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Formation and maintenance of high-nitrate, low pH layers in the eastern Indian Ocean and the role of nitrogen fixation

et al. 2013

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We investigated the biogeochemistry of low dissolved oxygen high-nitrate (LDOHN) layers forming against the backdrop of several interleaving regional water masses in the eastern Indian Ocean, off northwest Australia adjacent to Ningaloo Reef. These water masses, including the forming Leeuwin Current, have been shown directly to impact the ecological function of Ningaloo Reef and other iconic coastal habitats downstream. Our results indicate that LDOHN layers are formed from multiple subduction events of the Eastern Gyral Current beneath the Leeuwin Current (LC); the LC originates from both the Indonesian Throughflow and tropical Indian Ocean. Density differences of up to 0.025 kg m⁻³ between the Eastern Gyral Current and the Leeuwin Current produce sharp gradients that can trap high concentrations of particles (measured as low transmission) along the density interfaces. The oxidation of the trapped particulate matter results in local depletion of dissolved oxygen and regeneration of dissolved nitrate (nitrification). We document an associated increase in total dissolved carbon dioxide, which lowers the seawater pH by 0.04 units. Based on isotopic measurements (δ¹⁵N and δ¹⁸O) of dissolved nitrate, we determine that ~ 40–100% of the nitrate found in LDOHN layers is likely to originate from nitrogen fixation, and that, regionally, the importance of N-fixation in contributing to LDOHN layers is likely to be highest at the surface and offshore

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Section: Oceanographic History and Formation Of Ldohn Layersmentioning

confidence: 96%

Section: Primary Research Voyagementioning

confidence: 99%

Section: Primary Research Voyagementioning

confidence: 99%

Section: Fig 1 (A)mentioning

confidence: 99%

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Formation and maintenance of high-nitrate, low pH layers in the eastern Indian Ocean and the role of nitrogen fixation

et al. 2013

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“…This is a region of intense summer rainfall, significant terrestrial run-off and some of the lightest (warm and fresh ¼ low density) seawater on the planet (Durack and Wijffels 2010). Two tropical water sources, one from the equatorial Indian Ocean, via the South Java Current, and the other from the equatorial Pacific Ocean, via the ITF, join the westward flow of the South Equatorial Current in the top 100 m of the Indo-Australian Basin (Domingues et al 2007). The South Equatorial Current retroflects into the Eastern Gyral Current and expands into the pole-ward flowing eastern boundary flow of the Leeuwin Current.…”

Section: Oceanographymentioning

confidence: 99%

Baseline biogeochemical data from Australia's continental margin links seabed sediments to water column characteristics

Radke

Nicholas

Thompson

et al. 2017

Mar. Freshwater Res.

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Abstract. Surficial marine sediments are an important source of nutrients for productivity and biodiversity, yet the biogeochemistry of these sediments is poorly known in Australia. Seabed samples were collected at .350 locations in Australia's western, northern and eastern continental margins during Federal Government surveys . Parameters analysed included measures of organic matter (OM) source (d 13 C, d 15 N and C : N ratios), concentration (percentage total organic carbon, %TOC, and surface area-normalised TOC, OC : SA) and bioavailability (chlorin indices, total reactive chlorins, total oxygen uptake, total sediment metabolism (TSM), sediment oxygen demand (SOD) and SOD and TSM normalised against TOC). The aim of the present study was to summarise these biogeochemical 'baseline' data and make contextualised inferences about processes that govern the observed concentrations. The OM was primarily from marine sources and the OC : SA broadly reflected water column productivity (based on Moderate Resolution Imaging Spectroradiometer, MODIS). Approximately 40% of sediments were organic poor by global standards, reflecting seawater oligotrophy; ,12% were organic rich due to benthic production, high water column productivity and pockmark formation. OM freshness varied due to pigment degradation in water columns and dilution with refractory OM in reworked sediments. d 15 N values confirmed the importance of N 2 fixation to Timor Sea productivity, and point to recycling of fixed nitrogen within food chains in Western Australia.

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Salinity dominance on the Indian Ocean Eastern Gyral current

Menezes

Phillips

Schiller

et al. 2013

Geophysical Research Letters

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This study demonstrates the importance of salinity gradients to the formation of the Eastern Gyral Current (EGC) in the South Indian Ocean. The EGC flows eastward near 15∘S, opposite to the direction predicted by classical theories of wind‐driven circulation and is a source of water for the Leeuwin Current. In the upper ocean, a strong salinity front exists between fresh water from the Indonesian Throughflow (ITF) in the South Equatorial Current (SEC) and salty subtropical waters. In that region, salinity overwhelms the temperature contribution to density gradients, generating eastward geostrophic shear and establishing the EGC. Without the salinity front the EGC cannot be maintained: If the salinity contribution is neglected in the calculation of geostrophic currents, the EGC vanishes. Our observational analysis associated with the fact that both Sverdrup and Ekman theories produce westward flows in the region strongly supports the idea that the EGC is a salinity‐driven current.

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Simulated Lagrangian pathways between the Leeuwin Current System and the upper-ocean circulation of the southeast Indian Ocean

Cited by 137 publications

References 71 publications

Formation and maintenance of high-nitrate, low pH layers in the eastern Indian Ocean and the role of nitrogen fixation

Formation and maintenance of high-nitrate, low pH layers in the eastern Indian Ocean and the role of nitrogen fixation

Baseline biogeochemical data from Australia's continental margin links seabed sediments to water column characteristics

Salinity dominance on the Indian Ocean Eastern Gyral current

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