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[1] Topographic meandering of Antarctic Circumpolar Current (ACC) is found to be an impediment in the propagation of Antarctic Circumpolar Wave (ACW) in the Indian Ocean sector of Antarctica. Reasons for this are attributed to the southward advection of the ACW anomalies associated with the topographic meandering of the ACC. The southward meandering of ACC facilitates warming up of the region east of 20°E by about 1°C during winter, thereby reducing the sea ice; these processes interfere with the eastward propagating positive sea‐ice anomalies, and reduce its strength. Warming of ocean induced by topographic meandering leads to upward vertical velocities between 40°–60°E, where the ocean surface velocities are weak and southward, and the vertical/meridional advection of temperature dominates the zonal advection in the atmosphere. This results in the decoupling of the ACW in the region east of 40°E. In regions out side the Indian Ocean sector, vertical advection is minimum and zonal velocity of ACC becomes positive, which facilitates the ACW propagation in the Central Pacific, Ross and Weddell Seas. Citation: Nuncio, M., A. J. Luis, and X. Yuan (2011), Topographic meandering of Antarctic Circumpolar Current and Antarctic Circumpolar Wave in the ice‐ ocean‐atmosphere system, Geophys. Res. Lett., 38, L13708

[1] Seasonal variability of surface wind stress derived from SeaWINDS onboard the NASA's QuikSCAT satellite is mapped over the latitude range 30°–60°S in the Southern Ocean for the period from August 1999 to July 2003. Seasonal variability is pronounced on basin-wide scale which dominates the Atlantic-Indian Ocean sector during austral winter. Harmonic analysis reveals that seasonal harmonic captures larger than 60% of the variance on regional scales. The cyclonic wind stress curl induces divergence around Antarctica and facilitates ACC meandering equatorward in the Atlantic-Indian Ocean sector of the Southern Ocean.

Atmospheric convergence regions over the tropical Indian Ocean have been mapped for the first time using 31 years of vector wind data. The convergence fields reveal that the energetic summer monsoon winds enhance convergence in the central Arabian Sea and in the eastern Bay of Bengal when compared with weak winter monsoon winds. The summer monsoon is also effective in spatial migration of convergence regions in both basins. Area-integrated convergence time series reveals an annual cycle with high amplitude during summer monsoon, which occurs in phase with Indian rainfall. The study explores the prospects of using the convergence as one of the predictors of Indian rainfall.

[1] We report on sea surface temperature (SST) cooling in the Gulf of Oman during winter monsoon 1993 using evidence from the advanced very high resolution radiometer (AVHRR). A combination of the AVHRR SST and scatterometer-based momentum and heat fluxes is used to discuss the SST-cooling mechanism. Cold SST evolves in the gulf during an intense outbreak of wintertime winds. The turbulence generated by these winds in the surface atmospheric boundary layer depletes large heat from the sea surface and cause 1–2°C SST cooling during January–March. Additionally, the alongshore component of the wind stress promotes Ekman dynamics and further enhances SST cooling along the periphery of the gulf.

[1] Wintertime sea surface temperature (SST) cooling south of the Indian tip (hereafter tip) is investigated during a 14 day gap wind event (21 January to 3 February 1997) using satellite data and the three-dimensional, primitive equation, sigma coordinate Princeton Ocean Model (POM). The advanced very high resolution radiometer SST reveals surface cooling of 1.5°C over the 14 day period near west of Sri Lanka. A spatial-mean time series of surface forcing west of Sri Lanka indicate a bell-shaped pattern, which is characterized by maximum wind stress and outgoing heat flux (sum of turbulent heat flux and net surface long-wave radiation) of 0.12 N/m2 and 450 W/m2, respectively, on 27 January. POM simulation is performed with realistic bottom topography, with seasonal stratification, and with daily mean surface forcing derived from NASA scatterometer (NSCAT) winds and National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) meteorological variables. During 21–28 January, Ekman dynamics together with positive wind stress curl promote SST cooling along the west coast of Sri Lanka. Thereafter irregular and shallow topography near the tip promotes diapycnal mixing, and the characteristic surface circulation significantly influences the evolution of the SST pattern along the periphery of the tip. An anticyclonic circulation evolves in the Gulf of Mannar under the influence of local negative wind stress curl after 27 January. Examination of a zonal section of density and vertical heat diffusion reveals that the initial stratification in the vicinity of the tip weakens because of diapycnal mixing and vertical diffusion of the surface heat. The mixed layer heat budget near the west of Sri Lanka and south of the tip reveals that the surface heat depletion dictates SST changes throughout the event. From our earlier works [Luis and Kawamura, 2000, 2001] and from the results of the present investigation it is inferred that the wintertime SST cooling in the vicinity of the tip is a case of topography-monsoon-ocean interaction.