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Agulhas Current

The Agulhas Current is a strong, warm western boundary current in the southwestern Indian Ocean that flows southward along the southeastern coast of Africa, transporting approximately 60–70 Sverdrups (×10⁶ m³/s) of subtropical water and playing a pivotal role in inter-ocean exchange and global climate regulation.^[1]^[2] Originating from the confluence of the Mozambique Channel inflow and the East Madagascar Current, the Agulhas Current forms as a narrow, jet-like stream hugging South Africa's continental shelf, with surface velocities reaching up to 1.3 m/s and carrying 1–1.5 petawatts of heat southward.^[3]^[1]^[2] Its waters are characterized by high temperatures (up to 24–26°C at the surface) and elevated salinity (around 35.5–36 psu), which distinguish it from surrounding cooler, fresher Indian Ocean waters.^[1] As it rounds the Agulhas Bank off the southern tip of Africa, the current undergoes a dynamic retroflection near 20°E, forming a tight loop approximately 400 km in diameter that largely reverses direction to become the eastward-flowing Agulhas Return Current, while intermittently shedding 4–12 anticyclonic eddies (Agulhas Rings) per year into the South Atlantic.^[1] These rings, each transporting 2–15 ×10⁶ m³/s of volume, facilitate the leakage of 0.4–3.0 ×10⁶ m³/s of Indian Ocean water across the ocean boundary, injecting heat (0.034–0.945 petawatts) and salt (28–78 ×10¹² kg/year) into the Atlantic.^[1] This interbasin exchange is essential to the global thermohaline circulation, enhancing the Atlantic Meridional Overturning Circulation by compensating for freshwater inputs from the Arctic and supporting climate stability, including influences on sea surface temperatures, sea level rise along African coasts, and rainfall patterns in southeastern Africa and the Agulhas Ring region.^[3]^[2] The current's variability, driven by phenomena like Natal Pulses (upstream meanders) and topographic interactions, contributes to broader ocean-atmosphere interactions, such as modulating storm tracks and regional heat budgets in the southern hemisphere.^[1]

Geographical Overview

Path and Location

The Agulhas Current originates in the Mozambique Channel near 27°S latitude, where waters from the East Madagascar Current and Mozambique Channel eddies converge to form the nascent current.^[4] It then flows southward along the eastern continental margin of Africa, hugging the narrow shelf edge off the coasts of Mozambique, KwaZulu-Natal, and the Eastern Cape provinces of South Africa, maintaining close proximity to the shoreline—typically within 20-50 km offshore in its northern reaches.^[4] The trajectory continues parallel to the African shelf until approximately 34°S near Port Elizabeth, after which the current begins to separate from the coast as it approaches the broader Agulhas Bank, ultimately reaching its southern terminus at Cape Agulhas around 34.5°S before retroflecting eastward into the Indian Ocean.^[1] This overall path spans a latitudinal range of roughly 27°S to 40°S, tracing the southeastern African margin over a distance exceeding 1,500 km. Recent high-resolution modeling as of 2023 confirms the path's stability with minor variability influenced by atmospheric modes.^[4]^[5] The current's spatial extent features a relatively narrow width of approximately 100 km for its surface-intensified core, though it can broaden to 200-300 km including flanking anticyclonic recirculation zones, particularly over the Agulhas Bank.^[6] Vertically, it extends from the surface down to about 1000–1500 m, with the strongest flow confined to the upper 500 m, diminishing gradually with depth due to frictional effects.^[7] The Agulhas Bank, a wide (up to 250 km) and shallow (less than 200 m) submarine plateau extending southward from Cape Agulhas, marks a key transition where the current's path deviates offshore, influenced by the abrupt widening of the shelf.^[1] The current's trajectory is profoundly shaped by the regional bathymetry, including the steep continental slope (often exceeding 3° inclination) that borders the narrow African shelf (typically 10-30 km wide along much of its path), which constrains the flow and promotes its stability by limiting lateral excursions.^[4] In contrast, the Natal Bight—a broader indentation of the shelf around 30°S—introduces slight offshore deflections due to its gentler slope and increased width, though the overall path remains tightly bound to the shelf edge.^[4] Over the Agulhas Bank, the shallower bathymetry and expansive shelf facilitate the current's final westward swing and retroflection, creating a dynamic boundary between the Indian and Atlantic Oceans.^[1] Schematic maps of the Agulhas Current typically depict its route as a bold, curving arrow originating in the Mozambique Channel, paralleling the African coastline southward with minimal deviation until the Agulhas Bank, where it loops sharply eastward; these visualizations often highlight the shelf edge as a dashed line to emphasize the current's coastal adherence, with the retroflection zone marked by concentric eddies southwest of Cape Agulhas.^[4]

Formation and Driving Mechanisms

The Agulhas Current serves as the western boundary current of the Indian Ocean's subtropical gyre, a large-scale anticyclonic circulation pattern that dominates the basin's dynamics. This role aligns with classical theories of ocean circulation, where intense western boundary currents compensate for the broader, slower interior flow driven by wind patterns. The current's formation begins in the southwestern Indian Ocean, where it consolidates waters along the African continental margin, intensifying southward due to the gyre's vorticity balance.^[1] The primary drivers of the Agulhas Current are wind-forced, rooted in the Sverdrup balance that governs the subtropical gyre's transport. Southeast trade winds over the Indian Ocean generate negative wind stress curl, inducing Ekman transport that piles up water in the gyre's interior and necessitates a poleward western boundary current to close the circulation. This wind-driven mechanism accounts for the bulk of the current's volume transport, with interannual variability largely tied to fluctuations in the South Indian Ocean wind stress curl, explaining up to 47% of observed changes in the upper ocean layers. Thermohaline forcing supplements this by contributing to the density structure, though wind dominates the initiation.^[8]^[1] Waters feeding the Agulhas Current originate from multiple pathways within the Indian Ocean, blending tropical and subtropical influences. The Mozambique Channel provides a key inflow through a series of anticyclonic eddies that carry Tropical Surface Water (salinity below 35.55) and Tropical Thermocline Water from the equatorial and northern Indian Ocean, contributing approximately 22% of the current's volume. These eddies propagate southward, delivering about 0.5 Sv of high-salinity Red Sea Water (around 40 psu) formed by excessive evaporation in enclosed basins. Complementing this, the East Madagascar Current supplies subtropical waters, including Subtropical Surface Water (salinity maximum near 35.55 at density σθ = 25.8 kg/m³), accounting for roughly 24% of the transport and sourced from the gyre's eastern limb. Recirculating subtropical gyre waters, influenced by broader Indian Ocean inflows, make up the remaining 54%, integrating signals from remote tropical regions.^[9]^[10] Thermohaline contributions to the Agulhas Current arise from pronounced evaporation in the Indian Ocean subtropics (25°–35°S), which elevates surface salinity and promotes subduction of dense water masses into the thermocline. This process forms the high-salinity Subtropical Surface Water that ventilates the gyre and feeds the current's offshore core, enhancing its density-driven component. Salinity gradients, amplified by net freshwater loss in the northern Indian Ocean and Red Sea outflow, create a thermohaline conveyor that sustains the current's warmth and saltiness, influencing its overall stability within the gyre circulation.^[9]^[10]

Physical Properties

Flow Speed and Transport

The Agulhas Current attains its maximum surface speeds of up to 2.5 m/s (5.6 mph or 9.0 km/h) off the southeast coast of South Africa, where the current is narrow and intense near the continental shelf.^[11] These velocities reflect the current's role as one of the fastest western boundary currents in the Southern Hemisphere, driven by the steep pressure gradients associated with its warm water mass.^[12] The volume transport of the Agulhas Current is estimated at 60-70 Sverdrups (Sv, where 1 Sv = 10^6 m³/s) directed southward along the African shelf, representing a substantial flux of Indian Ocean water.^[13] This transport exhibits seasonal variations, typically strengthening during austral summer due to enhanced wind forcing and weakening in winter, though the overall magnitude remains dominated by the mean flow.^[14] The current transports warm tropical waters with surface temperatures ranging from 20°C to 28°C, which progressively cool southward as heat is lost to the atmosphere and mixing occurs with surrounding cooler waters.^[15] Salinity in the upper layers is characteristically high at 35-36 practical salinity units (psu), resulting from intense evaporation in the subtropical Indian Ocean source regions that exceed precipitation.^[10] Estimates of the current's flow speed and transport often rely on geostrophic balance, where the velocity v is approximated by the thermal wind relation:

v = \frac{g}{f} \int \frac{\partial \rho}{\partial n} \, dz

Here, g is gravitational acceleration, f is the Coriolis parameter, \rho is water density, n is the cross-stream direction, and the integral is over depth z. This equation captures the baroclinic structure driven by density gradients from temperature and salinity variations, providing a foundational method for quantifying the current's dynamics below the surface Ekman layer.^[12]

Meanders, Eddies, and Variability

The Agulhas Current displays prominent meanders, which are oscillatory deviations from its mean path, with typical wavelengths of 200–300 km in the mesoscale range. These meanders arise primarily from baroclinic instability, where vertical shear in the current's velocity structure generates perturbations that grow through the release of potential energy associated with density gradients.^[16] Observations indicate that such instabilities extract kinetic energy from the mean flow, leading to offshore excursions that can amplify over time, though smaller-scale meanders (around 100 km) often stabilize the jet by reinforcing the core flow.^[16] Baroclinic processes dominate in the upper layers, contributing to the current's dynamic variability along the South African shelf edge. A key manifestation of these meanders is the Natal pulses, solitary offshore perturbations originating near Durban in the Natal Bight, which propagate downstream at speeds of 10–20 km per day. These pulses occur intermittently with cycles typically spanning 50–240 days, though their active offshore phases last 10–70 days, inducing cyclonic circulation inshore of the current.^[17] Triggered by barotropic instability in the coastal region, Natal pulses grow to amplitudes of up to 300 km wide, displacing the current's axis seaward and modulating local shear.^[17] Their frequency averages 1–2 events per year, with southward propagation influencing downstream dynamics over distances exceeding 800 km.^[18] Eddy formation along the Agulhas Current stems from shear instabilities and interactions with bottom topography, producing both cyclonic and anticyclonic eddies. Cyclonic eddies often emerge from the inshore shear edge, particularly over the Agulhas Bank, where negative vorticity generates plumes of warm surface water and promotes upwelling.^[19] Anticyclonic eddies, conversely, form upstream in the Mozambique Channel and east of Madagascar through barotropic instability, traveling southward at 20–30 cm/s and contributing to the current's volume transport.^[20] Topographic features, such as the shelf break, enhance eddy shedding by amplifying shear, with cyclones typically shorter-lived and confined near the retroflection, while anticyclones propagate more extensively.^[20] The current's variability exhibits seasonal and interannual patterns, with meanders and pulses showing modulated frequencies tied to large-scale climate forcings. Seasonally, eddy kinetic energy peaks in austral summer due to enhanced barotropic instability, though the inshore edge remains relatively stable year-round.^[21] Interannually, Natal pulse occurrences vary from 1–2 events per year in the 1980s–1990s to over 3 post-2010, influenced by El Niño–Southern Oscillation (ENSO) through wind stress anomalies that alter upstream eddy propagation from the Mozambique Channel and south of Madagascar.^[22] During El Niño phases, increased westerly winds can elevate pulse frequency, amplifying offshore displacements.^[23] Recent 2025 observational studies using high-resolution satellite sea surface temperature data have highlighted eddy-driven inshore variability, revealing that Natal pulses and smaller "Durban eddies" induce recurrent cold anomalies and current reversals along the KwaZulu-Natal shelf. These features, detected via automated algorithms, show Durban eddies originating at ~4.3 events per year with lifespans under 10 days and speeds of ~22 km/day, while Natal pulses grow southward, reaching sizes up to 179 km.^[24] Such variability underscores the role of upstream eddies in modulating coastal dynamics, with cold events more prevalent due to enhanced mixing.^[24] Modeling corroborates these patterns, confirming that entrained eddies from the Mozambique Channel drive inshore fluctuations without strong seasonal modulation.^[24]

Retroflection and Leakage

The Agulhas Current undergoes retroflection at the southern tip of Africa, where it sharply turns eastward in a tight anticyclonic loop east of Cape Agulhas, separating the Indian Ocean from the Atlantic. This U-turn forms the Agulhas Return Current, which flows northeastward into the Indian Ocean, while a portion of the warm, saline water leaks westward into the Atlantic Ocean. The retroflection loop typically has a diameter of 300 to 400 km, corresponding to a radius of approximately 150 to 200 km, though it exhibits variability in position and extent based on satellite observations over multiple decades.^[4]^[25] The leakage through this retroflection region transfers an estimated 15 to 21 Sverdrups (Sv) of Indian Ocean water into the Atlantic, primarily via thin filaments extending from the loop and the shedding of Agulhas rings, which carry isolated parcels of water westward, with observational estimates around 21 Sv as of 2020.^[26]^[1] This volume represents a significant inter-ocean exchange, with the Indian Ocean contributing the majority (about 12.6 Sv) of the leaked water in model simulations validated against observations. The process is dynamic, with the loop occasionally protruding farther westward, enhancing leakage during periods of intensified current meandering.^[27]^[1] Several mechanisms govern the retroflection and associated leakage, including the wind stress curl that drives the upstream current, the beta effect from planetary vorticity gradients that influences the loop's shape and stability, and nonlinear interactions such as barotropic instabilities that promote filament formation and ring shedding. The beta effect, through southward planetary vorticity advection, counteracts inertial tendencies and helps maintain the loop's position, while nonlinear effects amplify variability in the shear zone. Historical observations from satellite altimetry, spanning over 20 years, reveal interannual variability in leakage anomalies, with fluctuations linked to changes in the retroflection latitude and wind forcing, showing no significant long-term trend during the altimetry era but decadal-scale oscillations.^[28]^[1]^[29]^[30] Recent analyses from eddy-rich Earth system models, such as the 0.1° resolution Community Earth System Model, indicate long-term trends in Agulhas leakage under climate change scenarios, with a projected increase of 0.08 Sv per decade from 1920 to 2100 due to strengthened and southward-shifted Southern Hemisphere westerlies. These models simulate a baseline leakage of 19.7 ± 3 Sv, aligning with observational estimates, and highlight enhanced salt transport (doubling to 0.7 Sv psu by 2100) that could influence global overturning circulation. Such trends underscore the retroflection's sensitivity to large-scale atmospheric changes.^[31]

Agulhas Undercurrent

The Agulhas Undercurrent is a subsurface equatorward flow that opposes the dominant poleward surface circulation of the Agulhas Current, occurring along the southeastern continental margin of South Africa. It is confined to depths ranging from approximately 800 m to 2500 m, directly beneath the surface core of the main current and hugging the continental slope. This counterflow is bottom-intensified, with its core typically centered around 1200–1400 m, where velocities can reach up to 50 cm/s.^[32]^[33] The undercurrent carries a transport of approximately 4–5 Sv northeastward (equatorward relative to the surface flow), representing a significant compensation for the overlying poleward transport and driven primarily by alongshore density gradients associated with the Indian Ocean's meridional overturning. The water masses composing this flow originate from Antarctic Intermediate Water (AAIW), which forms in the subantarctic zone and provides fresher, oxygen-rich intermediate layers, and Red Sea Water (RSW), a warmer, more saline intermediate water mass that enters via the Mozambique Channel. These water masses maintain distinct thermohaline signatures within the undercurrent, though mixing occurs due to shear with the surface current. Deeper components may include North Atlantic Deep Water (NADW), contributing to the overall equatorward ventilation of the Indian Ocean.^[34]^[35]^[36] The undercurrent's path is strongly influenced by bottom topography, remaining attached to the steep continental slope but becoming constrained or deflected by features such as the shallower Natal Valley north of 32°S, where depths drop below 2250 m. This topographic steering can promote localized upwelling of nutrient-rich intermediate waters onto the shelf, particularly during interactions with the slope. Observations from moored arrays, such as those deployed during the Agulhas Undercurrent Experiment (AUCE) at 32°S from 2003 to 2004, reveal high variability in the undercurrent's strength, with seasonal strengthening noted in austral winter, when equatorward NADW flow intensifies and overall transport increases due to enhanced density contrasts. These measurements, using current meters at depths up to 2900 m, recorded mean velocities of about 20 cm/s with standard deviations indicating episodic peaks tied to 50–60 day cycles.^[37]^[33]^[38]

Oceanographic Interactions

Agulhas Rings and Atlantic Exchange

The Agulhas rings form primarily through barotropic instability in the retroflection zone of the Agulhas Current, where the current loops back eastward after reaching the African continental shelf edge, leading to the periodic shedding of large anticyclonic eddies. This process generates approximately 5 to 9 rings per year, with an average rate of about 5.8 observed in satellite altimetry data spanning multiple decades.^[29]^[39] These rings represent a key mechanism for inter-ocean exchange, detaching parcels of warm, saline Indian Ocean water and injecting them westward into the South Atlantic. Characterized by diameters typically ranging from 200 to 300 km, Agulhas rings maintain coherence for 6 to 12 months, during which they propagate northwestward, often embedded within the Benguela Current and interacting with the Benguela upwelling system along the southwestern African margin. Each ring transports 1 to 3 Sv of volume, along with associated heat and salt anomalies, facilitating the transfer of roughly 10 to 15 Sv annually through ring-mediated leakage overall.^[40]^[41]^[42] This transport modulates thermohaline properties in the Atlantic, with rings decaying gradually—often rapidly in the first 5 months—while dispersing their signatures over broader scales. The influx of salty water via Agulhas rings influences the Atlantic Meridional Overturning Circulation (AMOC) by enhancing salinity in the South Atlantic, which strengthens the meridional density gradient and supports deep water formation through the salt-advection feedback mechanism. This feedback reduces the AMOC's sensitivity to freshwater perturbations, helping sustain the circulation against potential collapses.^[31]^[43] Recent coral-based proxy records from southwestern Madagascar reveal a 334-year span of variability in surface salinity and temperature within the greater Agulhas region, reflecting fluctuations in ring strength and leakage intensity over centennial timescales.^[44]

Paleoclimatic Significance

The Agulhas Current serves as a critical climate gateway facilitating the exchange of warm, saline water from the Indian Ocean into the Atlantic, influencing interhemispheric climate dynamics over geological timescales. This leakage modulates the salinity and temperature gradients essential for the Atlantic Meridional Overturning Circulation (AMOC), acting as a conduit that links subtropical heat to higher latitudes. Paleoclimatic records highlight its role in amplifying or dampening global climate shifts, particularly through variations in water mass transfer that affect ocean circulation and regional hydroclimate patterns.^[45] Proxy records from marine sediment cores, planktonic foraminifera, and coral δ¹⁸O analyses reveal millennia-scale fluctuations in Agulhas leakage intensity. For instance, a continuous 270,000-year record from sediment core CD154 10-06 P off the southeast African coast uses Mg/Ca ratios and δ¹⁸O in Globigerinoides ruber foraminifera to reconstruct sea surface temperature and salinity (δ¹⁸O_sw-ivc), showing elevated salinity during interglacials indicative of enhanced Indian-Atlantic water exchange and reduced salinity during glacials suggesting diminished leakage. These proxies demonstrate coherent variability tied to shifts in the position of the Subtropical Front, with leakage peaks aligning with warmer periods that promoted greater retroflection and eddy shedding. Coral δ¹⁸O records from southwestern Madagascar further corroborate these patterns on shorter timescales, capturing salinity anomalies driven by wind-forced upwelling and current strength.^[46]^[44] During glacial-interglacial cycles, Agulhas leakage exhibited pronounced enhancements at terminations, invigorating the AMOC and contributing to deglacial warming. Over the past 1.2 million years, 17 such leakage maxima occurred synchronously with ice-volume minima, as traced by the accumulation of Globorotalia menardii foraminifera in Ocean Drilling Program Site 1087 sediments, reflecting southward migration of the Subtropical Front and increased inter-ocean transfer. This strengthened leakage during interglacials, particularly in the last 450,000 years, supplied buoyant Indian Ocean water to the South Atlantic, facilitating AMOC resumption and heat transport to the North Atlantic, with a 400,000-year periodicity observed post-Mid-Pleistocene Transition.^[47] A 334-year coral record from Ifaty and Tulear reefs (1661–1995 CE), analyzed for Sr/Ca and δ¹⁸O, provides estimates of Agulhas Current strength variations, revealing multidecadal to centennial oscillations in surface salinity and temperature without a linear trend, dominated by interannual (2–4 years) and decadal (8–16 years) signals linked to large-scale wind forcing. These findings, extending insights into pre-industrial conditions, imply that historical current intensity followed natural climate swings, with implications for understanding Holocene leakage dynamics prior to modern anthropogenic influences. In the broader paleoclimate context, Agulhas variations have influenced the African monsoon and Indian Ocean Dipole (IOD) analogs, where reduced leakage around 3 million years ago warmed the western Indian Ocean, steepening zonal sea surface temperature gradients and altering eastern African hydroclimate through orbital obliquity-driven precipitation cycles.^[44]^[48]^[49]

Rogue Waves and Extreme Events

The Agulhas Current is notorious for generating rogue waves through nonlinear wave steepening in zones of intense current shear, where opposing wave propagation against the swift flow amplifies wave energy via modulational instability. This process is particularly pronounced when waves align counter to the current, leading to spectral broadening and heightened wave focusing, as demonstrated by high-resolution simulations of wave-current interactions in the region. The current's meanders further exacerbate this by creating localized shear gradients that concentrate energy, increasing the likelihood of extreme surface perturbations. Rogue waves in the Agulhas region typically exhibit heights at least twice the significant wave height (Hs), with documented cases exceeding 18 meters during stormy conditions, far surpassing open-ocean averages where such events are rarer. The Benjamin-Feir Index (BFI), a measure of instability potential, often exceeds critical thresholds (BFI > 1) in the current core and retroflection, signaling elevated rogue wave probability compared to background seas, where Hs values hover around 5-6 meters but can surge by 20-60% under opposing current influence. These waves are characterized by steep fronts, asymmetry, and rapid localization, posing disproportionate hazards due to their unpredictability. Historical records attribute numerous maritime disasters to Agulhas rogue waves in the 20th century, including the severe damage or sinking of approximately 30 large vessels along South Africa's southeast coast between 1981 and 1991, often linked to encounters near the 200-meter isobath during cold frontal passages. Seminal observations from the 1970s documented freak waves devastating ships in these shear zones, underscoring the current's role in wave amplification. Modeling efforts employ the Benjamin-Feir instability framework within spectral wave models like SWAN to forecast these events, validating predictions against satellite altimetry data with correlation coefficients above 0.95, enabling better assessment of risk in current-dominated areas. Recent 2025 research using the Surface Water and Ocean Topography (SWOT) mission has resolved sharper frontal structures in the Agulhas Current retroflection, revealing submesoscale features that intensify shear by up to 28%, potentially elevating extreme wave risks amid ongoing climate-driven variability.

Biological and Ecological Aspects

Primary Production

The core of the Agulhas Current is characterized by low primary production owing to its warm, oligotrophic surface waters, where chlorophyll-a concentrations are typically below 0.2 mg m⁻³. This nutrient-depleted environment, part of the South Indian Ocean subtropical gyre, supports minimal phytoplankton growth, with net primary production rates often under 1.0 g C m⁻² d⁻¹ in open ocean areas. Nano- and picophytoplankton dominate the sparse biomass, reflecting adaptation to low nutrient and light-limited conditions. In contrast, the adjacent Agulhas Bank exhibits enhanced primary production in upwelling zones, fueled by interactions between the current's meanders and wind-driven processes that introduce nutrients to the euphotic zone. Surface chlorophyll-a concentrations here range from 0.3 to 5.1 mg m⁻³, with elevated values inshore and near the shelf break, supporting net primary production of 0.3 to 1.1 g C m⁻² d⁻¹. These dynamics create sharp cross-shelf gradients, where oligotrophic offshore waters transition to more productive shelf environments. Nutrient sources for this productivity primarily stem from vertical mixing and entrainment of deeper waters via the Agulhas Undercurrent, which supplies nitrate (up to 26.9 μmol N L⁻¹ in bottom waters) and silicic acid from South Indian Ocean Central Water. Instabilities along the current, including meanders, promote upward nutrient flux, offsetting surface depletion and enabling localized phytoplankton blooms. Seasonal variability peaks in summer (January–March), when intense episodic shelf-edge upwelling generates chlorophyll-a concentrations of 5–25 mg m⁻³ in mature upwelled parcels, contrasting with weaker spring events. Satellite-derived chlorophyll maps from instruments like SeaWiFS highlight these gradients, showing extended maxima along the shelf and fronts from spring through fall, with winter minima in the core aligned to mixed-layer deepening and reduced light availability.

Marine Biodiversity

The Agulhas Current fosters a rich mosaic of marine habitats along South Africa's southeastern coast, particularly in shelf-edge environments where warm tropical waters interact with the continental shelf, promoting high species diversity. The Agulhas Bank, a broad and shallow extension of the shelf, supports diverse benthic and pelagic communities, including coral reefs that thrive in the relatively nutrient-enriched waters driven by current-induced upwelling. These reefs host a variety of reef-building and associated species, contributing to the region's status as a biodiversity hotspot within the Western Indian Ocean. One of the most iconic displays of this biodiversity is the annual sardine run, a mass migration of Sardinops sagax from their temperate spawning grounds off the Western Cape into subtropical waters along the KwaZulu-Natal coast, facilitated by cool-water filaments forming inshore of the Agulhas Current. This event aggregates billions of sardines, attracting a suite of predators and temporarily boosting local trophic interactions, including shoals of anchovies (Engraulis encrasicolus) and other pelagic fish. Marine mammals, such as migrating humpback whales (Megaptera novaeangliae), also utilize these productive corridors during their northward migration, feeding on krill and small fish concentrated by the current's dynamics.^[50] In 2025, large superpods of humpback whales were observed congregating off the South African coast, possibly influenced by oceanographic anomalies in the Agulhas system.^[51] The current's separation from the colder Benguela Current system creates a biogeographic barrier, enhancing endemism in the Agulhas ecoregion, where approximately 33% of South Africa's 12,914 known marine species are endemic, with peaks in the warm-temperate south coast habitats. Endemic elements include reef-associated fish like the endangered Petrus rupestris (red steenbras) and sharks such as the Rhinobatos ocellatus (speckled guitarfish), which find refuge in the shelf-edge reefs and seamounts influenced by the current. This isolation preserves unique assemblages, distinct from the upwelling-driven communities of the Benguela. Vertical zonation in the Agulhas system reflects temperature and nutrient gradients, with surface waters (20–28°C) supporting subtropical pelagic species like sardines and migratory cetaceans, while the undercurrent transports cooler, nutrient-replete waters from deeper layers, fostering distinct benthic biota such as mesophotic fish communities on the Agulhas Bank. These undercurrent-influenced habitats, including low-oxygen Red Sea Water intrusions, harbor specialized invertebrates and demersal fish adapted to intermediate depths, contrasting with the oligotrophic surface layer. Conservation efforts highlight the Agulhas region's vulnerability, with approximately 21.5% of the coastline and 5.4% of the mainland exclusive economic zone protected, as of 2024,^[52]^[53] despite its role as an endemism hotspot facing threats from ocean warming that could drive poleward range shifts of tropical species and disrupt endemic assemblages. Rising temperatures may exacerbate habitat loss in shelf-edge reefs and alter migration patterns of key species like humpback whales, underscoring the need for expanded marine protected areas to safeguard this biodiversity.

Impacts of Rings and Eddies on Ecosystems

Agulhas rings, formed during the retroflection process, inject nutrient-rich waters from the Indian Ocean into the southeastern Atlantic, particularly influencing the Benguela Current system by enhancing nutrient availability at eddy edges through submesoscale upwelling. This process elevates nitrate concentrations up to 4.0 μmol L⁻¹ and supports higher net primary production rates, such as 93.3 mmol C m⁻² d⁻¹, thereby boosting overall productivity in the region.^[54] Such offshore nutrient transport partially offsets reductions in carbon export potential within the Cape Basin, fostering a more dynamic nutrient cycling that benefits downstream ecosystems.^[54] Eddies generated along the Agulhas Current, including cyclonic features like Natal pulses, trap and retain planktonic larvae and meroplankton within their structures, creating localized hotspots of biological activity. The "suitcase hypothesis" describes how these eddies entrain meroplankton from coastal shelves, such as off Madagascar, transporting them across the Mozambique Channel to South African waters and promoting gene flow among separated populations.^[55] This retention mechanism concentrates zooplankton biovolumes up to 0.63 ml m⁻³ and supports patchy distributions of larvae from reef-associated species, enhancing local biodiversity and connectivity in the Agulhas ecosystem.^[55] Cross-shelf exchanges driven by eddies in the Agulhas Bank region facilitate the onshore transport of Indian Ocean species into coastal zones, with approximately 0.45 Sv of deep open-ocean waters entrained onto the shelf via upwelling and mixing events. Cyclonic eddies in the Agulhas Bank Bight promote the advection of fish eggs and larvae, such as those of Cape anchovy (Engraulis capensis), from eastern spawning grounds to nutrient-enriched western areas, altering species distributions along the South African coast.^[56] These exchanges, intensified during spring and summer, integrate subtropical biota into temperate coastal habitats, influencing community structure and ecological interactions.^[56] Over the long term, eddy-induced upwelling along the Agulhas Current enhances fisheries productivity by elevating chlorophyll concentrations and supporting higher trophic levels, as seen in increased catches of pelagic fish and squid linked to mesoscale activity. For instance, interactions between Agulhas waters and the shelf-edge generate upwelling filaments extending 100–500 km, which sustain nutrient supply for key commercial species like chokka squid (Loligo vulgaris reynaudii), vital to regional economies employing around 3,000 people.^[57] However, intensified eddy variability poses risks, including potential hypoxic conditions within ring centers due to high biological oxygen demand from elevated nitrification rates (up to 188% of nitrate uptake), which could stress enclosed microbial and faunal communities.^[54] Recent 2025 studies highlight how eddy variability inshore of the Agulhas Current affects inshore biodiversity, with Natal pulses and Durban eddies driving upwelling that enriches nutrients and promotes plankton blooms essential for higher trophic levels. Analysis of 40 years of satellite sea surface temperature data reveals that these features, occurring 1.6–5 times per year, induce coastal temperature fluctuations and enhance primary production, thereby supporting diverse inshore assemblages but also introducing instability to biodiversity patterns.^[58] Such variability underscores the role of eddies in shaping resilient yet vulnerable coastal ecosystems amid ongoing oceanographic changes.^[58]

Human and Climatic Dimensions

The Agulhas Current's high velocities, reaching up to 2 meters per second (approximately 4 knots), pose significant challenges for vessels navigating against its flow, leading to unintended drift that can push ships off course and increase fuel consumption by up to 25-50% depending on the ship's speed and the current's opposition.^[59]^[60] This drift is particularly problematic along the busy shipping lanes from Durban to Cape Town, where the current's southwestward push requires constant adjustments to maintain headings, exacerbating operational inefficiencies for cargo and tanker traffic in this high-volume corridor.^[61] In the retroflection zone near Cape Agulhas, the current amplifies risks from rogue waves, where opposing swells can increase wave heights by 20-60%, endangering shipping safety and contributing to historical wrecks such as the British East Indiaman Arniston in 1815, which foundered near the cape due to navigational errors compounded by strong winds and currents, resulting in over 370 lives lost.^[62]^[63] These extreme events, briefly noted in studies of physical ocean processes, have long made the area a notorious hazard for 19th-century sailing vessels attempting the clipper route around southern Africa.^[62] Mesoscale eddies along the current's margins further complicate navigation by creating variable flow patterns that disrupt radar detection and course plotting, as cyclonic eddies embedded in the landward boundary can alter surface velocities unpredictably, requiring vessels to rely on real-time data to avoid set-offs or collisions with coastal features.^[64]^[59] To mitigate these hazards, mariners use detailed current charts produced by the South African Navy Hydrographic Office, which provide essential data on flow speeds and eddy locations for route planning, supplemented by satellite-based observations from altimetry and AIS tracking that enable better prediction of drift and wave-current interactions.^[65]^[66] These tools have improved safety along the Durban-Cape Town lanes, allowing for more precise adjustments in high-traffic scenarios.^[61]

Climate Variability and Teleconnections

The Agulhas Current plays a pivotal role in the Indian Ocean Dipole (IOD) and monsoon variability through its export of heat from the subtropical Indian Ocean, which modulates sea surface temperatures (SSTs) and salinity patterns essential for atmospheric convection. By transporting warm, saline water southward at rates contributing approximately 30% of the Indian Ocean's heat export across 32°S, the current influences the regional heat budget, enhancing IOD intensity and linking to tropical Atlantic warming that amplifies dipole events.^[67] This volume transport via leakage, estimated at 10–20 Sv, affects monsoon precipitation by altering SST gradients that drive seasonal atmospheric circulation, with seasonal phasing of transport variations strengthening or weakening monsoon onset and duration.^[67] Studies indicate that increased eddy activity and wind-driven broadening of the current since the 1990s have sustained this influence without overall intensification.^[67] The Agulhas leakage serves as a modulator of the Atlantic Meridional Overturning Circulation (AMOC), acting as a potential "tipping element" for abrupt climate shifts by injecting warm, saline water into the South Atlantic, which can alter buoyancy and trigger AMOC recovery or weakening. High-amplitude salinity oscillations (up to ~1.5‰) in the leakage, observed on millennial scales during the Late Pleistocene, correlated with North Atlantic cold phases and facilitated interhemispheric coupling via Hadley Cell dynamics and westerlies, potentially resuming AMOC during stadial-to-interstadial transitions.^[68] This mechanism challenges northern hemisphere-centric views of abrupt changes, as strengthened leakage events raised SSTs by 2–5°C and influenced global overturning stability.^[68] On interannual timescales, Agulhas Current transport exhibits correlations with the Southern Annular Mode (SAM) and El Niño-Southern Oscillation (ENSO), driving variability in volume flux through wind stress anomalies. ENSO accounts for 11.5% of transport variance, with a correlation of 0.34 to the Niño-3.4 index, typically inducing 1–2 Sv changes, while SAM shows no significant direct correlation (r ≈ 0.1) despite influencing westerlies.^[69] Together with four other atmospheric modes, these explain 29% of interannual variance, with a standard deviation of 5.4 Sv and no detectable trend over recent decades amid SAM strengthening.^[69] Climate model projections from 2020–2025 indicate intensified Agulhas leakage under warming scenarios, with transport increasing by 0.08 Sv per decade through 2100 under RCP8.5, driven by southward-shifted and strengthened Southern Hemisphere westerlies. Salt transport via leakage is projected to double from preindustrial levels (~0.24 Sv psu) to ~0.7 Sv psu by end-century, while the current itself weakens by ~20 Sv due to reduced Indonesian Throughflow and gyre circulation.^[31] Teleconnections from the Agulhas Current to European weather arise through leakage-induced modulation of AMOC strength, which propagates salinity and heat anomalies northward, potentially stabilizing or destabilizing Atlantic circulation and influencing midlatitude weather patterns via advective pathways. Variations in leakage align with ice age/warm cycles, linking weakened Gulf Stream phases to altered European climate regimes, as evidenced by paleoclimate proxies and models showing interhemispheric impacts on precipitation and temperature.^[70] Although direct Rossby wave propagation from the Agulhas region remains less quantified, the current's SST anomalies contribute to broader atmospheric wave trains that extend teleconnections to the North Atlantic and Europe.^[43]

Economic and Renewable Energy Potential

The Agulhas Current plays a vital role in supporting South Africa's commercial fisheries, particularly the sardine industry, through its interactions with the continental shelf that promote nutrient-rich upwelling. Along the inshore edge of the current, particularly on the Agulhas Bank, wind-driven and current-induced upwelling events bring cold, nutrient-laden waters to the surface, fostering high primary productivity that sustains dense schools of sardines (Sardinops sagax). This upwelling is most pronounced during the sardine run, a seasonal migration where millions of tons of fish move northward along the KwaZulu-Natal coast, providing a critical harvest for purse-seine fisheries that contribute significantly to the national economy, with annual catches often exceeding 100,000 tons in productive years.^[71]^[72]^[73] Interactions between the Agulhas Current and the continental shelf also influence coastal geomorphology, including erosion patterns and beach dynamics along South Africa's southeast coastline. The current's strong southward flow, combined with meanders and eddies, generates shear stresses that enhance sediment transport and can accelerate shoreline erosion during periods of high wave energy or current instability. For instance, cyclic erosion events on the east coast, linked to the Agulhas' variability, exhibit an approximately 18-year periodicity, with peaks correlating to intensified current-shelf interactions that reshape beaches and dunes. In areas like Ponta do Ouro, Mozambique, the current's proximity to the shore contributes to dynamic beach accretion and erosion, affecting coastal infrastructure and sediment budgets.^[74]^[75]^[76] The Agulhas Bank's rich marine environment, influenced by the current's warm waters and upwelling zones, underpins a thriving tourism sector focused on ecotourism activities. Whale watching, particularly for southern right and humpback whales that calve in the sheltered bays, attracts thousands of visitors annually to sites like Walker Bay, generating substantial revenue through boat tours and shore-based observations. Dive sites on the Agulhas Bank, such as those near Gansbaai and Plettenberg Bay, offer access to diverse reefs and shark populations, with shark-cage diving becoming a signature experience that supports local economies via licensed operators and related services. These activities highlight the current's role in creating biodiverse hotspots that draw international tourists, contributing to South Africa's coastal tourism industry valued at billions of rands yearly.^[77]^[78]^[79] The Agulhas Current's high-velocity flow presents significant potential for marine renewable energy generation through ocean current turbines, offering a steady, predictable resource compared to wind or waves. Preliminary assessments indicate that a turbine array spanning 100 km along the current could harness up to 20 GW of power, leveraging flow speeds often exceeding 2 m/s in the core. Recent modeling for South African sites, including Buffels Bay, evaluates hybrid wind-tidal systems feasible for grid integration, with ongoing 2025 feasibility studies projecting a technical capacity in the 10-20 GW range for the broader Agulhas system, contingent on turbine advancements and environmental impact assessments. This potential aligns with global efforts to tap western boundary currents, where the Agulhas ranks among the most energetic, supporting South Africa's renewable energy goals.^[80]^[81]^[82] Monitoring efforts like the Agulhas System Climate Array (ASCA), deployed since 2016, enhance economic forecasting by providing real-time data on current variability that influences fisheries yields and coastal stability. The array's moorings track transport, temperature, and eddy formation, enabling predictions of upwelling events critical for sardine stock management and reducing economic losses from recruitment failures. By integrating ASCA observations with models, authorities can forecast impacts on sectors like tourism and energy development, informing policy for sustainable resource use in the face of climate-driven changes.^[83]^[84]^[85]

References

[1]
[PDF] The Agulhas Current retroflection
The southern termination of the Agulhas Current is unique for a western boundary current in this respect that it takes place at the meridional extremity of ...
[2]
Agulhas System Climate Array (ASCA) | Beal Lab | Rosenstiel School
The Agulhas Current is the western boundary current of the South Indian Ocean. It is strong and carries a large amount of heat.
[3]
[PDF] The Agulhas Current - Lamont-Doherty Earth Observatory
As the name suggests, the Agulhas Re- turn Current returns most of the Agul- has water back into the Indian Ocean— “most” but not all.
[4]
[PDF] Three decades of research on the greater Agulhas Current - OS
The only place along its path where this does not hold is at the Natal Bight, a wider part of the shelf in a coastal off- set north of Durban (see Fig. 3) ...
[5]
Atmospheric Signature of the Agulhas Current - AGU Journals - Wiley
Apr 19, 2018 · ... Agulhas Current and precipitation (Figure 1). The Agulhas Current is 80–100 km wide and runs south-westward along the eastern coast of South ...
[6]
The Atmospheric Boundary Layer above the Agulhas Current during ...
The current is between 1000 and 1500 m deep, between 90 and 100 km wide, and ... Agulhas Current was investigated in the Agulhas Current Air–Sea Exchange ...
[7]
Atmospheric driving forces for the Agulhas Current in the subtropics
Aug 7, 2007 · The Agulhas Current is the western boundary current of the South Indian Ocean and is thought to play an important role in the global ...
[8]
The Sources and Mixing Characteristics of the Agulhas Current
The waters of the Agulhas Current originate from disparate sources. Most are from various reaches of the Indian Ocean, including Red Sea Water (RSW) and ...
[9]
The Agulhas Current Transports Signals of Local and Remote Indian ...
Feb 23, 2023 · The Agulhas Current derives its waters from three source regions; the Mozambique Channel, the South East Madagascar Current, and recirculating ...Missing: path | Show results with:path
[10]
Drift observations from Nimbus VI satellite-tracked buoys in the ...
The maximum buoy drift speed in the Agulhas Current of 260cm s−1 was confirmed by shipborne current measurements.
[11]
[PDF] Structure and downstream evolution of the Agulhas Current system ...
Mar 5, 2003 · [5] Beal and Bryden [1999] showed that the Agulhas Current at 32°S was in geostrophic balance below 200 m, with a full water column transport ...
[12]
Evidence that Agulhas Current transport is maintained during a ...
Jun 9, 2014 · The Agulhas Current (AC) is the strongest western boundary current (WBC) in the Southern Hemisphere with an average transport of 70 Sv (1 Sv ...
[13]
Large-Scale Forcing of the Agulhas Variability: The Seasonal Cycle in
Seasonal changes of the transport of the Agulhas Current are linked to the large-scale circulation in the tropical region. According to the model, the Agulhas ...
[14]
Agulhas Current properties shape microbial community diversity and ...
Jul 12, 2018 · Here we assess microbial diversity, community structure and functional capacity along the Agulhas Current system and the Subtropical Front in the South Indian ...
[15]
Characteristics, Energetics, and Origins of Agulhas Current ...
The Agulhas Current intermittently undergoes dramatic offshore excursions from its mean path because of the downstream passage of mesoscale solitary meanders ...
[16]
Generation and Evolution of Natal Pulses: Solitary Meanders in the ...
Abstract. Solitary meanders of the Agulhas Current, so-called Natal pulses, may play an important role in the overall dynamics of this current system.
[17]
New perspectives on Natal Pulses from satellite observations
Jul 16, 2011 · ... Current equalled 10.2 days, with Natal Pulses lasting between 50 and 70 days. ... Natal Pulses per year reach the southern Agulhas Current. The ...
[18]
Modelling the shear edge eddies of the southern Agulhas Current
The model simulates the creation of cyclonic shear edge eddies and their attendant surface plumes of warm water along the edge of the Agulhas Bank with a high ...
[19]
The Role of Mesoscale Eddies in the Source Regions of the Agulhas Current
### Summary of Eddy Formation in Agulhas Current
[20]
Seasonal Variability of Eddy Kinetic Energy in the Greater Agulhas ...
Jan 28, 2025 · Seasonal cycle of eddy kinetic energy in the greater Agulhas Current system (GACS) is spatially inhomogeneous Barotropic instability plays ...
[21]
[PDF] Journal Pre-proof - Archimer
Oct 17, 2025 · Improved algorithm enhances eddy detection inshore of Agulhas Current. ○ First occurrences of Agulhas waters detected using automated method. ○ ...
[22]
Interannual Variability of the Natal Pulse - AGU Journals - Wiley
Dec 10, 2019 · We show that variations of the Natal Pulse are mainly explained by variations of eddies propagating from the south of Madagascar and the Mozambique Channel.1 Introduction · 4 Sources Of The Natal Pulse · 4.2 Trigger Of The Natal...
[23]
Characterisation of the eddy-driven variability inshore of the Agulhas Current using sea surface temperature observations
### Summary of 2025 Research on Eddy-Driven Inshore Variability in the Agulhas Current
[24]
The Retroflection of the Agulhas Current in - AMS Journals
On average the Agulhas retroflection lies between 16° and 20°E longitude and has a loop diameter of 340 km.
[25]
Indian Ocean sources of Agulhas leakage - AGU Journals - Wiley
Apr 13, 2017 · The IO contributes 12.6 Sv to Agulhas leakage, which within the model is 14.1 ± 2.2 Sv, the rest originates from the South Atlantic.
[26]
[PDF] dynamics of agulhas retroflection and ring formation in a ... - fsu/coaps
First, the physical mechanism of the model retroflection is presented through illustration of the Agulhas' vorticity balance among various experiments, and ...
[27]
Agulhas ring formation as a barotropic instability of the retroflection
Oct 9, 2013 · Agulhas ring formation reflects an instability of the retroflection · The mechanism is a barotropic instability of the shear zone · The ...<|separator|>
[28]
An observed 20-year time series of Agulhas leakage - OS
Jul 3, 2014 · We provide a time series of Agulhas leakage anomalies over the last 20-years from satellite altimetry. Until now, measuring the interannual ...
[29]
Long-term variability and trends in the Agulhas Leakage and its ... - OS
Jan 21, 2025 · Agulhas Leakage transports relatively warm and salty Indian Ocean waters into the Atlantic Ocean and as such is an important component of ...
[30]
The Sources and Mixing Characteristics of the Agulhas Current
Aug 6, 2025 · ... Agulhas Undercurrent is observed flowing equatorward below 800 m depth, directly beneath the surface core of the poleward flowing Agulhas ...
[31]
Agulhas Undercurrent Experiment (AUCE)
The Agulhas Undercurrent Experiment (AUCE) comprised an oceanographic survey off the east coast of South Africa between 28°S and 37°S and a moored array at 32° ...Missing: range interaction upwelling seasonal<|control11|><|separator|>
[32]
The Sources and Mixing Characteristics of the Agulhas Current in
The waters of the Agulhas Current originate from disparate sources. Most are from various reaches of the Indian Ocean, including Red Sea Water (RSW) and ...Missing: geography | Show results with:geography
[33]
Red Sea Intermediate Water in the source regions of the Agulhas ...
The annual mean transport of RSIW through the strait is about 0.33 Sv with strong seasonal variations (from ∼0.05 Sv in summer to >0.7 Sv in winter (1 Sv=106 m ...
[34]
Red Sea Intermediate Water at the Agulhas Current termination
Transport measurements of intermediate water masses calculated by You et al. (2003) indicate a net transport of 0.3 ± 1 Sv of RSIW eastward down the Agulhas ...
[35]
A Time Series of Agulhas Undercurrent Transport in - AMS Journals
For an Indian Ocean overturning transport in the region of 10 Sv (McDonagh et al. 2008), the Agulhas Undercurrent represents about 20% of the ventilation of the ...
[36]
First Observations of Seasonal Variability in Water Mass Properties ...
Sep 6, 2022 · In winter, when the Agulhas Current is relatively weaker and shallower than in summer, we observe more equatorward flow of the deepest water ...
[37]
[PDF] Spatio-temporal characteristics of the Agulhas Current retroflection
Agulhas ring formation at an average yearly rate of 5.8, similar to previous findings, was observed to occur west of 19°E, in the western half of the ...
[38]
On the translation of Agulhas rings to the western South Atlantic Ocean
Juvenile Agulhas rings are large anticyclonic eddies with a mean diameter of 242 ± 38 km (Duncombe Rae, 1991) and depths that can reach 4.5 km (van Aken et al. ...Missing: lifespan | Show results with:lifespan
[39]
Characteristics and evolution of an Agulhas ring - AGU Journals
Aug 11, 2017 · The rotational transport inside the ring was 33 Sv in the thermocline and intermediate layers. The drifters' data distinguish a 30-km core ...Missing: lifespan | Show results with:lifespan
[40]
[PDF] Three Agulhas rings observed during the Benguela Current ...
Sep 15, 1999 · Two are typical Agulhas rings surveyed at different times after their generation; the third Agulhas ring has an anomalous water mass structure ...
[41]
Impact of Agulhas Leakage on the Atlantic Overturning Circulation in ...
In this model an advective connection exists that transports salinity anomalies from the Agulhas region into the North Atlantic on decadal (30–40 yr) time ...
[42]
A 334-year coral record of surface temperature and salinity ... - CP
Jun 27, 2022 · A 334-year (1661–1995) reconstruction of δ 18 O seawater changes related to surface salinity variability in the wider Agulhas Current region.
[43]
The Agulhas Leakage: the missing link in the interhemispheric ...
Agulhas Leakage (AL) is a fraction of the Agulhas Current that escapes into the South Atlantic, transporting warm, saline water from the Indian Ocean.
[44]
A late Pleistocene dataset of Agulhas Current variability - PMC
Nov 11, 2020 · Here we present a new continuous 270-kyr data set consisting of Agulhas Current near-surface temperature and inferred salinity based on surface- ...
[45]
Agulhas leakage as a key process in the modes of Quaternary ...
Apr 16, 2012 · Strengthening of the Agulhas leakage may have induced a resumption of the AMOC during terminations and a more vigorous AMOC during the ...
[46]
Corals track strongest Indian Ocean Current over 334 years
Natural variations in the warming and cooling cycles of the globally important Agulhas ocean current core region have been revealed from Madagascar corals.
[47]
High‐Latitude, Indian Ocean, and Orbital Influences on Eastern ...
Nov 30, 2023 · We propose that northward migration of the Subtropical Front reduced Agulhas current leakage, warming the western IO and causing changes in the ...
[48]
https://www.geomar.de/en/news/article/corals-track-strongest-indian-ocean-current-over-334-years
[49]
The Influence of Agulhas Leakage on Primary Production and ...
Sep 14, 2022 · The chlorophyll-a concentrations thus appear to record no eddy-related trends in phytoplankton size structure. This may be because eddy biology ...Introduction · Materials and Methods · Results · Discussion
[50]
(PDF) African Journal of Marine Science The 'suitcase hypothesis'
Dec 21, 2017 · larvae and one fish larva were identified using 16S rDNA. These included phyllosoma larvae of the genera Scyllarus. and Panulirus (Table 4), and ...
[51]
Circulation and Cross‐Shelf Exchanges in the Agulhas Bank Region
Jan 3, 2025 · Seasonal changes of the thermohaline structure due to upwelling favorable winds are largely confined to the easternmost region during the summer ...
[52]
The role of the Agulhas in the Benguela Current system: A numerical ...
Mar 28, 2017 · The Benguela system is unique as one of the world's four major eastern boundary upwelling systems due to its proximity to a western boundary ...Missing: trajectory | Show results with:trajectory
[53]
Characterisation of the eddy-driven variability inshore of the Agulhas ...
Oct 23, 2025 · In this study, mechanisms causing year-to-year changes in the Florida Current seasonality are investigated using controlled realistic numerical ...
[54]
Monitoring the Agulhas Current Through Maritime Traffic - Eos.org
Jun 28, 2021 · Researchers typically use radar altimeters, which send a microwave pulse toward the ocean and measure the time it takes to rebound, to study the ...
[55]
Global Energy-saving Map of Strong Ocean Currents | The Journal ...
Jun 22, 2015 · Theoretically, the WBCs with speeds of 2–3 knots can reduce fuel consumption by 25–50% for vessels at a sailing speed of 6 knots. The fuel ...
[56]
The Challenge of Passage Planning in the SW Indian Ocean
Richards Bay/Durban to Cape Town. Once safely in Richards Bay or Durban, the next challenge is to negotiate the South African coast round to Cape Town. The ...
[57]
Toward Operational Wave‐Current Interactions Over the Agulhas ...
Jun 8, 2020 · In opposing current scenarios, the significant wave height can increase by 20–40% and by 60% in extreme cases. Model validation is performed ...
[58]
A list of South African Shipwrecks
Oct 18, 2011 · The ship was wrecked near Cape Agulhas on 30 April as a result of navigational mistakes and strong winds. Only 6 people survived the tragedy.
[59]
Benefits of radar-derived surface current assimilation for South of ...
Jan 20, 2021 · Lutjeharms et al. (2003) observed the presence of cyclonic eddies embedded in the landward border of the southern Agulhas Current. These eddies ...
[60]
SA Navy Hydrographic Office
Information page for the South African Navy Hydrographic Office. Notices to mariners, chart information, tide information and coastal warnings for Navarea ...Paper Charts · Charts for usage band: General · Notices to Mariners · Products
[61]
Monitoring the Greater Agulhas Current With AIS Data Information
Apr 29, 2021 · Early studies have shown the relevance of using AIS information and ship trajectory analysis to estimate surface currents (Guichoux, 2015; van ...
[62]
Progress in understanding of Indian Ocean circulation, variability, air–sea exchange, and impacts on biogeochemistry
Below is a merged summary of the Agulhas Current's role in Indian Ocean Dipole (IOD) and monsoon variability via heat export, consolidating all information from the provided segments into a comprehensive response. To maximize detail and clarity, I’ve organized the key information into a table in CSV format, followed by a narrative summary that integrates the findings and provides additional context. This approach ensures all data, citations, quotes, and URLs are retained while maintaining readability.
[63]
Agulhas salt‐leakage oscillations during abrupt climate changes of ...
Jun 27, 2013 · Results presented in this study indicate that transient and high-amplitude oscillations of the Agulhas salt leakage were a persistent feature of ...
[64]
Observed Agulhas Current Sensitivity to Interannual and Long-Term ...
Of the interannual variance of the Agulhas Current transport, 29% can be linearly related to six modes of Southern Hemisphere atmospheric variability.
[65]
The Agulhas Current and Europe's climate | Results in Brief | FP7
Sep 28, 2015 · At the southern tip of the continent, immediately before entering the South Atlantic it turns around and flows back into the Indian Ocean.
[66]
Linking the movement of South African sardine and anchovy to ...
The environment-linked models use sea surface temperature (SST) and an upwelling index for the southern Benguela and Agulhas Bank as drivers. SST and upwelling ...Missing: industry | Show results with:industry
[67]
Upwelling at the inshore edge of the Agulhas Current - ResearchGate
Evidence for upwelling along the landward side of the Agulhas Current is presented. An analysis of old and new hydrographic data, surface temperature ...
[68]
Shelf currents, lee-trapped and transient eddies on the inshore ...
Aug 6, 2025 · CTD data indicated that this was associated with shelf-edge upwelling, with surface temperatures 2–4 °C cooler than the adjacent core ...
[69]
Forecasting cyclic coastal erosion on a multi-annual to multi-decadal ...
Oct 5, 2014 · Coastal erosion on the southeast African coastline shows an apparent 18 year cycle which last peaked in 2006.
[70]
Coastal climate and beach dynamics at Ponta do Ouro, Mozambique
Aug 10, 2025 · Topics covered include weather and wind, the influence of the Agulhas Current, coastal ... beach camp to assess management and interactions.
[71]
Observations of northeastward flow on a narrow shelf dominated by ...
Apr 5, 2021 · Agulhas Current (AC) extended inshore to 3.2 km from the coast off Port Edward. •. Minimal influence of local wind forcing on currents and ...<|control11|><|separator|>
[72]
South Africa - ScienceDirect
The Agulhas Slope and seamounts include the outer margin of the Agulhas Bank and has been recognized as a spawning area for commercially important fish species ...
[73]
Marine Biodiversity in South Africa: An Evaluation of Current States ...
Aug 2, 2010 · Along the east coast, the warm Agulhas Current brings nutrient-poor, tropical waters southward from the equatorial Indian Ocean. The current is ...
[74]
(PDF) On the origin of Agulhas Bank water - ResearchGate
... tourism value of the bay contributes substantially to the country's economy, and whale watching, shark-cage diving and water sports have become important ...
[75]
[PDF] Energy Technologies for the 21st Century-The Roles of Renewable ...
Aug 2, 2005 · From preliminary investigations for the Agulhas current off the coast of South Africa—the swiftest sea current in the world—it was estimated ...<|separator|>
[76]
(PDF) Cost Optimization Model for a Grid-Connected Offshore Wind ...
Sep 26, 2025 · This study presents a cost optimization model for a grid-connected offshore wind and tidal power generation system, using Buffels Bay, South ...
[77]
Drifter-based global ocean current energy resource assessment
The Kuroshio energy capacity is estimated to be about 24 GW for an area of 120 km 2 [20]. Based on data from three numerical models, the mean power potential ...
[78]
[PDF] Global Perspectives on Observing Ocean Boundary Current Systems
Aug 8, 2019 · These systems are home to intense and highly variable oceanic currents that redistribute mass, heat, salt, biogeochemical constituents, plankton ...
[79]
The importance of monitoring the Greater Agulhas Current and its ...
We highlight progress of the new Agulhas System Climate Array, as well as the South African Meridional Overturning Circulation programme, which includes the ...Missing: forecasting | Show results with:forecasting
[80]
[PDF] A roadmap to sustained observations of theIndian Ocean for 2020 ...
The goal of IndOOS is to provide sustained high-quality oceanographic and marine meteorological measurements that can support knowledge-based decision-making ...