- Dona Paula, Goa, India.
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- iiosc2020[at]nio[dot]org
| Abstract Submission No. | ABS-2022-11-0311 |
| Title of Abstract | A comprehensive study of the Indo-Pacific seesaw in the intraseasonal barotropic sea level |
| Authors | M Afroosa*, B. Rohith, Fabien Durand, Arya Paul, Romain Bourdalle-Badie, S.S.C. Shenoi |
| Organisation | Indian National Center for Ocean Information Services (INCOIS) |
| Address | Indian National Center for Ocean Information Services (INCOIS) Hyderabad, Telangana, India Pincode: 500090 Mobile: 9496517189 E-mail: afroosa04@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | At intraseasonal time scales, Madden Julian Oscillation (MJO) wind driven see-saw in the Indo-Pacific oceanic mass has been reported during boreal winters and its impact on polar motion. The present study is a detailed investigation on understanding the dynamics behind the see-saw. During the positive phase of see-saw, the barotropic sea level in the Indian ocean rises and the Pacific ocean falls and vice versa during the negative phase. Here, from a numerical model we show the intraseasonal barotropic circulation that facilitates the seesaw. During the positive phase, the MJO winds over the maritime continent drives a large-scale anticlockwise circulation of ~ 2 Sv around the Australian Continent that gives rise to a barotropic sea level rise in the Indian Ocean. Simultaneously, it also drives a clockwise circulation in the southern Pacific Ocean leading to a barotropic sea level fall. This circulation pattern reverses during the negative phase of the seesaw. Based on a sensitivity experiment, we demonstrate that ITF plays an important role in conveying the barotropic signals associated with the see-saw. The closure of ITF straits in the model has led to the collapse of see-saw, which concludes that ITF is the pivotal point of see-saw. Among the major straits (Timor, Ombai and Lombok) of ITF, majority of transport occurs through Lombok and Ombai straits. We also found that it takes about a week to activate the seesaw once the Madden-Julian Oscillation winds reach the Maritime Continent. Here,we also illustrate the wave dynamics responsible for the near instantaneous barotropic sea level response in the Indo-Pacific basin. This dynamics involves fast propagating Rossby (planetary & topography) and Kelvin waves traveling across the Indo-Pacific basin within a few days which is in strong contrast to earlier estimates of months derived from slower baroclinic dynamics. We also show that see-saw is not a result of the intraseasonal variability in the climatological winds. See-saw is reproducible across various ocean models and therefore is robust. |