Relative role of <scp>E</scp>l <scp>N</scp>iño and IOD forcing on the southern tropical <scp>I</scp>ndian <scp>O</scp>cean <scp>R</scp>ossby waves

Chakravorty, Soumi; Gnanaseelan, C.; Chowdary, Jasti S.; Luo, Jing–Jia

doi:10.1002/2013jc009713

Cited by 49 publications

(28 citation statements)

References 46 publications

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“…The analysis of these data confirms that the ITF increases during La Nina and decreases during El Nino, but this effect is often weakened by in‐phase wind forcing in the Indian Ocean associated with the Indian Ocean Dipole (IOD; Feng et al, ; Liu et al, ; Wijffels et al, ). The IOD is well coupled to ENSO but not always in‐phase with ENSO (Cai et al, ; Chakravorty et al, ). Stuecker et al () find that about a third of IOD events occur independently of ENSO.…”

Section: Data Viewsmentioning

confidence: 99%

Makassar Strait Throughflow Seasonal and Interannual Variability: An Overview

et al. 2019

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The Makassar Strait throughflow of ~12–13 Sv, representing ~77% of the total Indonesian Throughflow, displays fluctuations over a broad range of time scales, from intraseasonal to seasonal (monsoonal) and interannual scales. We now have 13.3 years of Makassar throughflow observations: November 1996 to early July 1998; January 2004 to August 2011; and August 2013 to August 2017. Strong southward transport is evident during boreal summer, modulated by an ENSO interannual signal, with weaker southward flow and a deeper subsurface velocity maximum during El Niño; stronger southward flow with a shallower velocity maximum during La Niña. Accordingly, the southward heat flux, a product of the along‐channel current and temperature profiles, is significantly larger in summer and slightly larger during La Niña. The southward flow relaxed in 2014 and more so in 2015/2016, similar though not as extreme as during the strong El Niño event of 1997. In 2017, the throughflow increased to ~20 Sv. Since 2016, the deep layer, 300‐ to 760‐m southward transport increases, almost doubling to ~7.5 Sv. From mid‐2016 into early 2017, the transports above 300 m and below 300 m are about equal, whereas previously, the ratio was about 2.7:1. Near zero or northward flow occurs in the upper 100 m during boreal winter, albeit with interannual variability. Particularly strong winter reversals were observed in 2014/2015 and 2016/2017, the latter being the strongest winter reversal revealed in the entire Makassar time series.

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Section: Data Viewsmentioning

confidence: 99%

Makassar Strait Throughflow Seasonal and Interannual Variability: An Overview

et al. 2019

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“…() and Chakravorty et al . () have addressed the impact of El Nino on the Indian Ocean sea level variability through atmospheric bridge using coupled model sensitivity experiments. In this study, we designed the ocean model experiments only to quantify the El Nino impact through oceanic pathways (or ITF).…”

Section: Impacts Of Local Forcing and Influence From The Pacific Oceanmentioning

confidence: 99%

The interannual sea level variability in the Indian Ocean as simulated by an Ocean General Circulation Model

Deepa

Gnanaseelan

Kakatkar

et al. 2017

Intl Journal of Climatology

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The study finds that co‐occurrence years (years when IOD and El Niño events co‐occur) contribute significantly towards the interannual variability in the Indian Ocean. Carefully designed Ocean General Circulation Model (OGCM) captured the observed variability. The OGCM experiments are carried out by modulating the forcing fields over the Pacific and the Indian Ocean to understand the physical mechanisms causing sea level variability in the Indian Ocean. Decadal variability in the ENSO is primarily contributing to the decadal variability in the Indian Ocean sea level.

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“…7f)in the 297 eastern basin, associated with the anomalous equatorial easterlies. This wind curl induces 298 an anomalous Ekman downwelling and a deepening of the thermocline, which co-299propagate towards the west as Rossby waves (e.g.,Chakravorty et al, 2014; Figs. 7d, f).…”

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confidence: 99%

Seasonality and Predictability of the Indian Ocean Dipole Mode: ENSO Forcing and Internal Variability

et al. 2015

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24This study evaluates the relative contributions to the Indian Ocean Dipole (IOD) 25 mode of interannual variability from the El Niño-Southern Oscillation (ENSO) forcing 26 and ocean-atmosphere feedbacks internal to the Indian Ocean. The ENSO forcing and 27 internal variability is extracted by conducting a 10-member coupled simulation for 1950-28 2012 where sea surface temperature (SST) is restored to the observed anomalies over the 29 tropical Pacific but interactive with the atmosphere over the rest of the world ocean. In 30 these experiments, the ensemble mean is due to ENSO forcing and the inter-member 31 difference arises from internal variability of the climate system independent of ENSO. 32These elements contribute one third and two thirds of the total IOD variance, respectively. 33Both types of IOD variability develop into an east-west dipole pattern due to Bjerknes 34 feedback and peak in September-November. The ENSO forced and internal IOD modes 35 differ in several important ways. The forced IOD mode develops in August with a broad 36 meridional pattern, and eventually evolves into the Indian Ocean Basin mode; while the 37 internal IOD mode grows earlier in June, is more confined to the equator and decays 38 rapidly after October. The internal IOD mode is more skewed than the ENSO forced 39 response. The destructive interference of ENSO forcing and internal variability can 40 explain early-terminating IOD events, referred to IOD-like perturbations that fail to grow 41 during boreal summer. 42Our results have implications for predictability. Internal variability, as represented 43 by pre-season sea surface height anomalies off Sumatra, contributes to predictability 44considerably. Including this indicator of internal variability, together with ENSO, 45improves the predictability of IOD. 46 3

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Relative role of El Niño and IOD forcing on the southern tropical Indian Ocean Rossby waves

Cited by 49 publications

References 46 publications

Makassar Strait Throughflow Seasonal and Interannual Variability: An Overview

Makassar Strait Throughflow Seasonal and Interannual Variability: An Overview

The interannual sea level variability in the Indian Ocean as simulated by an Ocean General Circulation Model

Seasonality and Predictability of the Indian Ocean Dipole Mode: ENSO Forcing and Internal Variability

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