Impact of Indian ocean dipole on the coastal upwelling features off the southwest coast of India

Abstract. An index of El Niño Southern Oscillation (ENSO) in the Pacific during pre monsoon season is shown to account for a significant part of the variability of coastal Sea Surface Temperature (SST) anomalies measured a few months later within the wind driven southwest coast of India coastal upwelling region 7° N–14° N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and north Indian Oceans, leading to warm (cold) ENSO events being associated with relaxation (intensification) of the Indian trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Arabian Sea. The ability to use this teleconnection to give warning of large changes in the southwest coast of India coastal upwelling few months in advance is successfully tested using data from 1998 and 1999 ENSO events.

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Satellite and Argo Observed Surface Salinity Variations in the Tropical Indian Ocean and Their Association with the Indian Ocean Dipole Mode

Journal of Climate ◽

10.1175/jcli-d-14-00435.1 ◽

2015 ◽

Vol 28 (2) ◽

pp. 695-713 ◽

Cited By ~ 27

Author(s):

Yan Du ◽

Yuhong Zhang

Keyword(s):

Indian Ocean ◽

Ocean Circulation ◽

Indian Ocean Dipole ◽

Coastal Upwelling ◽

Tropical Indian Ocean ◽

Sea Surface Salinity ◽

The South ◽

Surface Salinity ◽

Indian Ocean Dipole Mode ◽

The Indian Ocean

Abstract This study investigates sea surface salinity (SSS) variations in the tropical Indian Ocean (IO) using the Aquarius/Satelite de Aplicaciones Cientificas-D (SAC-D) and the Soil Moisture and Ocean Salinity (SMOS) satellite data and the Argo observations during July 2010–July 2014. Compared to the Argo observations, the satellite datasets generally provide SSS maps with higher space–time resolution, particularly in the regions where Argo floats are sparse. Both Aquarius and SMOS well captured the SSS variations associated with the Indian Ocean dipole (IOD) mode. Significant SSS changes occurred in the central equatorial IO, along the Java–Sumatra coast, and south of the equatorial IO, due to ocean circulation variations. During the negative IOD events in 2010, 2013, and 2014, westerly wind anomalies strengthened along the equator, weakening coastal upwelling off Java and Sumatra and decreasing SSS. South of the equatorial IO, an anomalous cyclonic gyre changed the tropical circulation, which favored the eastward high-salinity tongue along the equator and the westward low-saline tongue in the south. An upwelling Rossby wave favored the increase of SSS farther to the south. During the positive IOD events in 2011 and 2012, the above-mentioned processes reversed, although the decrease of SSS was weaker in magnitude.

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The influence of tropical Indian Ocean warming and Indian Ocean Dipole on the surface chlorophyll concentration in the eastern Arabian Sea

10.5194/bg-2019-169 ◽

2019 ◽

Cited By ~ 1

Author(s):

Syam Sankar ◽

Anoop Thondithala Ramachandran ◽

Kemgang Ghomsi Franck Eitel ◽

Dmitry Kondrik ◽

Radharani Sen ◽

...

Keyword(s):

Indian Ocean ◽

Indian Ocean Dipole ◽

Arabian Sea ◽

Coastal Upwelling ◽

Chlorophyll Concentration ◽

Ocean Warming ◽

Oceanic Circulation ◽

Western Basin ◽

Indian Ocean Warming ◽

Eastern Arabian Sea

Abstract. This study examines the role of increased Indian Ocean warming and positive Indian Ocean Dipole (IOD) events on the surface chlorophyll concentration in the Eastern Arabian Sea (EAS) during the period 1998 to 2014. Remotely sensed surface chlorophyll concentration – during the month of October when IOD strength is maximum – at three selected areas in the EAS, viz., the central eastern Arabian Sea (CEAS, 73° E–76° E, 13° N–18° N), south eastern Arabian Sea (SEAS, 74° E–77° E, 8° N–13° N) and the southern tip of India (TIP, 74° E–78° E, 5° N–8° N) shows a steady decreasing trend, though not statistically significant. The EAS also has a higher warming trend when compared to the western basin during the study period. Our analysis has shown that in the EAS, local surface winds, remote forcing by equatorial winds and the surface and sub-surface oceanic circulation features are less (respectively more) favorable for inducing coastal upwelling during positive (respectively negative) IOD years. The Dipole Mode Index (DMI) and surface chlorophyll concentration in the EAS is significantly and negatively correlated, pointing to the fact that in the event of occurrence of frequent positive IOD years under a global warming regime, the surface chlorophyll concentration is likely to decrease during fall.

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