Relating a Large‐Scale Variation of Waves in the Indian Ocean to the IOD. Issue 10 (4th October 2022)

• Record Type: Journal Article
• Authors: Li, Rui; Wu, Kejian; Li, Jingkai; Dong, Xianghui; Sun, Jian; Zhang, Wenqing; Liu, Qingxiang
• Is Part Of: Journal of geophysical research. Volume 127:Issue 10(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-10-04
• Subjects: Stokes drift -- IOD -- wave transport -- swell -- wind wave; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2022JC018941
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: This study used the ERA‐5 40‐year reanalysis data set from the European Centre for Medium‐Range Weather Forecasts to analyze the spatial characteristics of wind waves and swells in the Indian Ocean. Although swells from the Southern Ocean can propagate into the Bay of Bengal, the zonal surface Stokes drift has been shown to correlate well with wind waves. Investigation of the relationship between the Indian Ocean Dipole (IOD) and the surface Stokes drift revealed strong correlation in the tropical Indian Ocean. The surface Stokes drift plays a positive role in maintaining sea surface temperature stability by transporting more (less) abnormally cold water during periods of positive (negative) IOD events. The depth‐integrated wave transport is quantified by the spectra and bulk parameters, respectively. Although two methods provide estimates of the same order of magnitude, the transport value is larger when wave spectra are used. With this approach, the estimated wave transport is comparable to the Ekman transport and its zonal component is even greater for more than 80% of the sea areas in the Indian Ocean; thus, it would have substantial effect on sea surface temperature. This paper proposes a new idea for studying this climatic phenomenon by considering the large‐scale wave effect, which builds a bridge for energy transport between the eastern and western boundaries of the Indian Ocean. Plain Language Summary: The Indian Ocean is closed on three sides and open only to the Southern Ocean. Swells from the Southern Ocean can propagate to the northern Indian Ocean, but the spatial distribution of the surface Stokes drift (i.e., wave‐induced current) is related to that of wind waves. The Indian Ocean Dipole (IOD) describes an irregular variation in sea surface temperature in which western parts of the Indian Ocean become alternately abnormal warming and cooling comparing with southeastern parts. In the tropical Indian Ocean, the abnormal surface Stokes drift has strong correlation with the IOD. During IOD events, the depth‐integrated Stokes drift can transport abnormally cold water to the area where sea surface temperature decreases anomalously, promoting stability of the tropical sea surface temperature. In quantifying the magnitude of wave transport, we found that it was comparable to the Ekman transport and its zonal component was even larger in the Indian Ocean. Because Ekman transport is one of the main processes of water transport in the upper ocean, we suggest that wave transport cannot be ignored when interpreting corresponding physical processes in the upper Indian Ocean. Key Points: Although swells from the Southern Ocean propagate northward for a long distance, the zonal surface Stokes drift is related to the wind waves Stokes drift plays a positive role in maintaining the zonal stability of sea surface temperature at low latitudes in the Indian Ocean Wave transport is of the same order of magnitude as Ekman transport and its zonal component is greater for more than 80% of the sea areas