caa a22 4500 605475040 CHVBK 20210128100350.0 cr unu---uuuuu 210128e20150501xx s 000 0 eng 10.1007/s00382-014-2379-y doi (NATIONALLICENCE)springer-10.1007/s00382-014-2379-y Tropical Indian Ocean subsurface temperature variability and the forcing mechanisms [Elektronische Daten] [Ojha Sayantani, C. Gnanaseelan] The first two leading modes of interannual variability of sea surface temperature in the Tropical Indian Ocean (TIO) are governed by El Niño Southern Oscillation and Indian Ocean Dipole (IOD) respectively. TIO subsurface however does not co-vary with the surface. The patterns of the first mode of TIO subsurface temperature variability and their vertical structure are found to closely resemble the patterns of IOD and El Niño co-occurrence years. These co-occurrence years are characterized by a north-south subsurface dipole rather than a conventional IOD forced east-west dipole. This subsurface dipole is forced by wind stress curl anomalies, driven mainly by meridional shear in the zonal wind anomalies. A new subsurface dipole index (SDI) has been defined in this study to quantify the intensity of the north-south dipole mode. The SDI peaks during December to February (DJF), a season after the dipole mode index peaks. It is found that this subsurface north-south dipole is a manifestation of the internal mode of variability of the Indian Ocean forced by IOD but modulated by Pacific forcing. The seasonal evolution of thermocline, subsurface temperature and the corresponding leading modes of variability further support this hypothesis. Positive wind stress curl anomalies in the south and negative wind stress curl anomalies in the north of 5°S force (or intensify) downwelling and upwelling waves respectively during DJF. These waves induce strong subsurface warming in the south and cooling in the north (especially during DJF) and assist the formation and/or maintenance of the north-south subsurface dipole. A thick barrier layer forms in the southern TIO, supporting the long persistence of anomalous subsurface warming. To the best of our knowledge the existence of such north-south subsurface dipole in TIO is being reported for the first time. Springer-Verlag Berlin Heidelberg, 2014 Indian Ocean nationallicence Subsurface variability nationallicence IOD nationallicence El Nino nationallicence Interannual variability nationallicence Sayantani Ojha Indian Institute of Tropical Meteorology, 411008, Pune, India aut Gnanaseelan C. Indian Institute of Tropical Meteorology, 411008, Pune, India aut Climate Dynamics Springer Berlin Heidelberg 44/9-10(2015-05-01), 2447-2462 0930-7575 44:9-10<2447 2015 44 382 https://doi.org/10.1007/s00382-014-2379-y text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00382-014-2379-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sayantani Ojha Indian Institute of Tropical Meteorology, 411008, Pune, India aut NATIONALLICENCE 700 1- Gnanaseelan C. Indian Institute of Tropical Meteorology, 411008, Pune, India aut NATIONALLICENCE 773 0- Climate Dynamics Springer Berlin Heidelberg 44/9-10(2015-05-01), 2447-2462 0930-7575 44:9-10<2447 2015 44 382