See-Saw in the Indo-Pacific Oceanic Mass
Afroosa Balkies BAI M1,2, B Rohith3, Fabien Durand4, Paul Arya1, Romain RB Bourdallé-Badie SR5, Laurent Testut6, Sreedevi Puthiyamadam7, Valerie Ballu8, Olivier de Viron9 and S. S. C. Shenoi10, (1)Indian National Center for Ocean Information Services, Hyderabad, India, (2)Kerala University of Fisheries and Ocean Studies, School of Ocean Sciences and Technology, Cochin, India, (3)Indian National Center for Ocean Information Services, Ocean modeling and data assimilation, Hyderabad, India, (4)LEGOS/IRD, Toulouse, France, (5)Mercator Ocean International, Ramonville, France, (6)LIENSs, UMR 7266, La Rochelle, France, (7)Cochin University of Science and Technology, Cochin, India, (8)Laboratoire Littoral Environnement et Sociétés (LIENSs), La Rochelle, UMR 7266, La Rochelle, France, (9)U. La Rochelle, LIENSs, La Rochelle, France, (10)Indian National Centre for Ocean Information Services, Hyderabad, India
Abstract:
Driven by Madden-Julian Oscillation (MJO), a significant basin-wide intraseasonal barotropic variability in sea level anomaly in the Tropical Indian Ocean (TIO), has been recently identified. Here we examine whether this barotropic variability modulates the intraseasonal barotropic sea level in the Pacific Ocean as well. Using observations and Ocean General Circulation Models (OGCM), we demonstrate that the barotropic variability is not only confined to the Indian Ocean, but also modulates the intraseasonal barotropic sea level anomaly in the Pacific Ocean causing a see-saw of mass in the Indo-Pacific basin. The pivotal point of this see-saw lies in the Indonesian straits. It appears that the adjustment mechanism of the Pacific involves barotropic Kelvin and Rossby waves, travelling across the Pacific basin in a few tens of hours.
The barotropic dynamics causes a inter-basin mass redistribution at intraseasonal time scales, in the form of 2 Sv (approx.) variability in the Indonesian Throughflow (ITF). This large-scale mass redistribution modulates the ocean angular momentum and hence alters the earth orientation parameters. We conclude that the intraseasonal meridional movement of water across the Pacific Ocean during boreal MJO cycle induces a significant change in earth wobbles, exciting in particular polar motions along the Y component with peak variability of ~ 60 cm, that dominate the overall polar motions forced by the entire (atmosphere + ocean) fluid system. Thus the results presented here, not only improves the general understanding of the Indo-Pacific dynamics but also have significant implications for geodesy.
