Interannual variability of zonal currents in the equatorial Indian Ocean: respective control of IOD and ENSO

Sachidanandan, Chinnu; Lengaigne, Matthieu; Muraleedharan, P.M.; Mathew, Basil

doi:10.1007/s10236-017-1061-4

Cited by 16 publications

(7 citation statements)

References 49 publications

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“…Although climate modes such as the Indian Ocean Dipole (IOD) are associated with zonal current variability in the Indian Ocean (Schott et al, 2009;Nagura and McPhaden, 2010;Sachidanandan et al, 2017), any effect on potential connectivity in our simulation is negligible compared to seasonality and stochastic variability.…”

Section: Seasonal Variabilitymentioning

confidence: 99%

High-frequency variability dominates potential connectivity between remote coral reefs

Vogt-Vincent

Mitarai

Johnson

2023

Preprint

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Abstract. Coral larval dispersal establishes connectivity between reefs, but larval fluxes vary over timescales from daily to multidecadal due to oceanographic variability. Using a 2 km-resolution ocean model, we simulate daily spawning events from 1993–2019 (for a total of almost 10,000 events) across all coral reefs in the tropical southwest Indian Ocean. Although there is a significant seasonal cycle in potential connectivity at many reefs, day-to-day variability generally dominates. The importance of this day-to-day variability depends on the local geography and oceanography. Stochastic oceanographic variability introduces considerable uncertainty to dispersal predictions, imposing significant limitations on what dispersal simulations can tell us about connectivity. Protracted spawning over only a few days can significantly reduce variability associated with the likelihood of a larva settling successfully. The duration of spawning is therefore likely a more important parameter in modelling coral connectivity than the exact timing of spawning onset. Finally, we find that a small proportion of spawning events account for the majority of successfully settling larvae, particularly at remote islands, and demonstrate that a time-mean picture of dispersal may be inappropriate for predicting demographic and genetic connectivity.

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Section: Seasonal Variabilitymentioning

confidence: 99%

High-frequency variability dominates potential connectivity between remote coral reefs

Vogt-Vincent

Mitarai

Johnson

2023

Preprint

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“…This transient feature of the EUC also determines the semiannual variations of zonal volume transport in the EIO, with the maximum eastward subsurface transport occurring in April and October (Nyadjro and McPhaden, 2014). The EUC shows a remarkable interannual variability and is significantly modulated by the Indian Ocean dipole (IOD) (Nagura and McPhaden, 2010;Zhang et al, 2014;Sachidanandan et al, 2017). Gnanaseelan and Deshpande (2018) showed that the enhancement and eastward extension of the EUC during strong IOD events could intensify and maintain the IOD through the intensification of oceanic responses.…”

Section: Introductionmentioning

confidence: 99%

Biases and improvements of the boreal winter–spring equatorial undercurrent in the Indian Ocean in the CMIP5 and CMIP6 models

Wang

et al. 2023

Front. Mar. Sci.

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We assessed the performance of state-of-the-art coupled models in reproducing the equatorial undercurrent (EUC) in the Indian Ocean based on the outputs of the Coupled Model Intercomparison Project Phase 6 (CMIP6) models and compared with the Phase 5 (CMIP5) models. Our results showed that the CMIP6 models reproduced the boreal winter–spring Indian Ocean EUC more realistically than the CMIP5 models, although both generations of models underestimated the strength of the Indian Ocean EUC compared with the observations. This underestimation of the Indian Ocean EUC can be attributed to the excessively strong and westward-extended cold tongue in the equatorial Pacific. In the CMIP models, a stronger winter-mean cold tongue favors a stronger zonal sea surface temperature gradient, which forces a strong easterly wind bias over the equatorial western Pacific. This, in turn, contributes to an acceleration of the Walker circulation. This enhanced Walker circulation over the Indo-Pacific Ocean directly causes a lower level westerly wind bias over the equatorial Indian Ocean and drives a shallow west–deep east thermocline tilt bias, ultimately leading to an excessively weak EUC in the Indian Ocean via wind-induced thermocline processes. Compared with the CMIP5 models, the overall improvement in the strength of the winter–spring Indian Ocean EUC in the CMIP6 models can be traced back to the improvement in the degree of the strong and westward-extended cold tongue bias. Our results suggest that efforts should be made to reduce the bias in the mean-state equatorial Pacific sea surface temperature to further improve the simulation and projection of the atmospheric and oceanic circulations in the Indian Ocean.

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“…In the IPWP, there are several major surface zonal currents, including the North Equatorial Countercurrent (NECC) (Chen et al., 2016; Kessler & Kleeman, 2000), Southwest Monsoon Current (SMC) (Schott et al., 2009), North Equatorial Current (NEC) (Chen & Wu, 2012; Qiu & Lukas, 1996) and South Equatorial Current (SEC) (Fine et al., 1994; Johnson et al., 2002). On seasonal and interannual time scales, ocean currents can be significantly influenced by ENSO, IOD, and Indian Ocean basin‐wide warming by modulating equatorial winds and oceanic internal variations (Nyadjro & McPhaden, 2014; Sachidanandan et al., 2017; Wang, 2019). The multiscale variabilities in these currents can lead to heat convergence/divergence in the IPWP, which not only likely feedbacks to the MISO over the Pacific Ocean (Lee et al., 2022; Yang et al., 2020) but also has profound implications for the climate and local environment.…”

Section: Introductionmentioning

confidence: 99%

Intraseasonal Variability of Surface Circulation in the Indo‐Pacific Warm Pool Induced by Summer Monsoon Intraseasonal Oscillations

Song

Wang

et al. 2022

JGR Oceans

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The Indian summer monsoon intraseasonal oscillation (MISO) is the most influential mode of tropical atmospheric intraseasonal variability in boreal summer (May–October). This study investigates how the MISO drives the intraseasonal variability (ISV) of zonal currents (U) in the Indo‐Pacific warm pool (IPWP) region. An analysis of satellite observations confirms a close association between U ISV and the MISO, with MISO‐induced surface U anomalies reaching 16–19 cm s−1 near the equator and 4–5 cm s−1 in the Northern Hemisphere portion of the IPWP. These ISVs account for 15%–35% of the intensity changes in the major zonal currents. The spatial distribution of U ISV shows coherent enhancement and suppression of MISO convections with a lag of approximately 7 days as a delayed response to the tropical wind forcing. ISV anomalies show northward emanation following propagation of the MISO. Ocean model experiments confirm that large‐scale ISV in surface U is primarily caused by the wind forcing of the MISO. Owing to the convergence/divergence of MISO‐induced U ISV, significant warm water volume anomalies occur in the western‐to‐central equatorial Pacific.

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Interannual variability of zonal currents in the equatorial Indian Ocean: respective control of IOD and ENSO

Abstract: International audienc

Cited by 16 publications

References 49 publications

High-frequency variability dominates potential connectivity between remote coral reefs

High-frequency variability dominates potential connectivity between remote coral reefs

Biases and improvements of the boreal winter–spring equatorial undercurrent in the Indian Ocean in the CMIP5 and CMIP6 models

Intraseasonal Variability of Surface Circulation in the Indo‐Pacific Warm Pool Induced by Summer Monsoon Intraseasonal Oscillations

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