Structure and dynamics of the Indian-Ocean cross-equatorial cell

Miyama, Toru; McCreary, Julian P.; Jensen, Tommy G.; Loschnigg, Johannes; Godfrey, Stuart; Ishida, Akio

doi:10.1016/s0967-0645(03)00044-4

Cited by 130 publications

(174 citation statements)

References 27 publications

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“…Even though Ekman balance breaks down near the equator, the near linearity of the zonal wind stress anomalies there (Fig. 6b) does not drive strong Ekman suction or pumping, and the surface flow crosses the equator (as in Miyama et al 2003). The anomalous Ekman mass transports plotted in Fig.…”

Section: Coupling Of the Atmosphere And Oceanmentioning

confidence: 87%

“…Near the equator, the surface branch is confined to the first model level, but in the grid cells immediately surrounding the equator, the southward flow spreads to the second model level (not shown) and slightly cooler temperatures. Because of its shallow depth, the Indian Ocean equatorial roll resides mostly in the weakly stratified mixed layer and does not significantly contribute to cross-equatorial energy transport in the Indian Ocean (Schott et al 2002;Miyama et al 2003). From the perspective of its cross-equatorial energy transport, then, the Indian Ocean CEC is an analog of our anomalous CEC, with warm water moving southward near the surface and cooler water subducted by Ekman pumping returning northward in a western boundary current in the thermocline.…”

mentioning

confidence: 90%

“…This NH cooling would push the ITCZ southward, damping the initial northward shift. Hemispherically asymmetric wind stress patterns drive cross-equatorial near-surface flow and energy transports in, for example, the Indian Ocean in the annual mean (Miyama et al 2003) and the global ocean over the seasonal cycle (Jayne and Marotzke 2001).…”

Section: Introductionmentioning

confidence: 99%

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Coupling of Trade Winds with Ocean Circulation Damps ITCZ Shifts

2017

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The position of the intertropical convergence zone (ITCZ) is sensitive to the atmosphere's hemispheric energy balance, lying in the hemisphere most strongly heated by radiative and turbulent surface energy fluxes. This study examines how the ocean circulation, through its cross-equatorial energy transport and associated surface energy fluxes, affects the ITCZ's response to an imposed interhemispheric heating contrast in a coupled atmosphere-ocean general circulation model. Shifts of the ITCZ are strongly damped owing to a robust coupling between the atmosphere's Hadley cells and the ocean's subtropical cells by the trade winds and their associated surface stresses. An anomalous oceanic wind-driven cross-equatorial cell transports energy across the equator, strongly offsetting the imposed heating contrast. The circulation of this cell can be described by the combination of trade wind anomalies and the meridional gradient of sea surface temperature, which sets the temperature contrast between its upper and lower branches. The ability of the wind-driven ocean circulation to damp ITCZ shifts represents a previously unappreciated constraint on the atmosphere's energy budget and indicates that the position of the ITCZ may be much less sensitive to interhemispheric heating contrasts than previously thought. Climatic implications of this damping are discussed.

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Section: Coupling Of the Atmosphere And Oceanmentioning

confidence: 87%

mentioning

confidence: 90%

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Coupling of Trade Winds with Ocean Circulation Damps ITCZ Shifts

2017

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“…Recent studies also reveal that multiscale air-sea interactions between intraseasonal and interannual variations are important processes in this key region [Rao and Yamagata, 2004;Shinoda and Han, 2005] as well as in the western tropical Pacific. However, studies on the ISV in the ocean, so far, mainly focus on the zonal current and associated temperature variability and there are relatively few studies for the meridional currents despite their importance for the meridional heat and salt transport across the equator and for the shallow meridional overturning cell in the equatorial Indian Ocean [Miyama et al, 2003].…”

Section: Introductionmentioning

confidence: 99%

Intraseasonal meridional current variability in the eastern equatorial Indian Ocean

et al. 2008

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[1] Intraseasonal variability in meridional current in the eastern equatorial Indian Ocean is investigated by use of results from a high-resolution ocean general circulation model. Both the simulated and observed meridional current variability demonstrate energy peaks in two distinct time-scales; one in the biweekly (6-8 d) period above the thermocline and the other in lower frequency band (20-70 d) within the subsurface layer. In addition, the intraseasonal current variability can be seen even in the deep ocean at 2000 m and 4000 m depths. Composite analysis of the biweekly current field demonstrates that the horizontal structure is consistent with the one for the Mixed Rossby-gravity wave, with the phase speed and wavelength close to theoretical values of the Mixed Rossby-gravity wave at 15-d period. This meridional current variability shows large coherence with the local meridional wind stress, suggesting the upper-ocean responses to the local wind-forcing. A part of the energy of the biweekly variability penetrates into the deeper layer along the raypath of the 15-d Mixed Rossby-gravity wave, causing the intraseasonal variability observed in the current meter data at 4000 m depth. On the other hand, the lower frequency intraseasonal variability in the subsurface layer is also captured in the model simulation forced by climatological winds. Large barotropic energy conversion rate appears during boreal autumn and early winter in a region southeast of Sri Lanka, suggesting importance of instability due to the seasonally changing current systems to generate mesoscale eddy-like disturbances that result in the subsurface meridional current variability.

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“…The strong subsurface northward flow in the Somali Current, which has its origin in the southern Indian Ocean and the Indonesian Throughflow, provides a source for upwelling in the northern Indian Ocean. Since this water subsequently is advected southward by Ekman transport, a shallow overturning cell is part of this gyre circulation (Miyama et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Wind-Driven Response of the Northern Indian Ocean to Climate Extremes*

Jensen

2007

Journal of Climate

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Composites of Florida State University winds for four different climate scenarios are used to force an Indian Ocean model. In addition to the mean climatology, the cases include La Niña, El Niño, and the Indian Ocean dipole (IOD). The differences in upper-ocean water mass exchanges between the Arabian Sea and the Bay of Bengal are investigated and show that, during El Niño and IOD years, the average clockwise Indian Ocean circulation is intensified, while it is weakened during La Niña years. As a consequence, high-salinity water export from the Arabian Sea into the Bay of Bengal is enhanced during El Niño and IOD years, while transport of low-salinity waters from the Bay of Bengal into the Arabian Sea is enhanced during La Niña years. This provides a venue for interannual salinity variations in the northern Indian Ocean.

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Structure and dynamics of the Indian-Ocean cross-equatorial cell

Cited by 130 publications

References 27 publications

Coupling of Trade Winds with Ocean Circulation Damps ITCZ Shifts

Coupling of Trade Winds with Ocean Circulation Damps ITCZ Shifts

Intraseasonal meridional current variability in the eastern equatorial Indian Ocean

Wind-Driven Response of the Northern Indian Ocean to Climate Extremes*

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