Two decades of current observations in the equatorial Indian Ocean

Blue-shifted deep ocean currents in the equatorial Indian Ocean

“…These jets are known to be driven by zonal winds with current speeds that can peak more than 2 m s −1 . The impact of these winds are stronger in the top 200-300 m below which strong upward phase propagation is evident (Jain et al 2021;McPhaden et al 2015). Our study shows that the dominance of the semi-annual cycle does not extend till the bottom of the ocean, particularly in the eastern Indian Ocean.…”

“…1b-d). The standard deviation is 4.2 cm s −1 at 77 • E and drops to 3.2 cm s −1 at 93 • E. In comparison, the maximum magnitude is greater than 100 cm s −1 for near-surface currents and decreases to 30-50 cm s −1 at intermediate depths of 200-1000 m (Jain et al 2021).…”

“…We used data from the deep-sea equatorial mooring programme, which is under Ocean Observation Network (OON) programme of ESSO-Indian National Centre for Ocean Information Services (INCOIS), India (Jain et al 2021). The currents were measured at three locations: 77 • E, 83 • E, and 93 • E (Fig.…”

“…The data at 93 • E were available only till 2014. The details of mooring configuration and data availability are available in Jain et al (2021).…”

Energetic Bottom Current at the Equatorial Gap of the Ninety East Ridge in the Indian Ocean Based on Mooring Data

“…Further, to identify the potential origin of the ISV of the bottom current at NR, we first compared the geostrophic current of the surface ocean to the bottom current at NR to evaluate the correlation between the motions of the upper ocean and the bottom layer; and we found no obvious correlation (∼0.01) between them, indicating that the variability of the bottom current at NR could not be directly induced by local mesoscale or large‐scale motions in the upper ocean. In fact, previous studies revealed the ubiquity of ISV in the upper ocean of the equatorial Indian Ocean, and wind‐forced oscillations in the upper ocean of the equatorial Indian Ocean, that is, remote wind‐forced Yanai wave (Miyama et al., 2006; Nagura & McPhaden, 2012; Ogata et al., 2008; Sengupta et al., 2004), the equatorial Kelvin waves or reflected Rossby waves (Amol et al., 2022), which could propagate vertically into the subsurface ocean; and some of them could penetrate the pycnocline and leak into the deep layer (Kessler & McCreary, 1993; McCreary, 1984), causing the ISV in the deep layer (Amol et al., 2022; David et al., 2011; Greatbatch et al., 2018; Jain et al., 2021; Ménesguen et al., 2019; Murty et al., 2006; Rothstein et al., 1985). In light of these previous studies, we speculate that the ISV of the bottom current at NR be associated with some remote forcing in the equatorial Indian Ocean.…”