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The El Niño-Southern Oscillation (ENSO) is modulated by many factors; most previous studies have emphasized the roles of wind stress and heat flux in the tropical Pacific. Freshwater flux (FWF) is another environmental forcing to the ocean; its effect and the related ocean salinity variability in the ENSO region have been of increased interest recently. Currently, accurate quantifications of the FWF roles in the climate remain challenging; the related observations and coupled ocean-atmosphere modeling involve large elements of uncertainty. In this study, we utilized satellite-based data to represent FWF-induced feedback in the tropical Pacific climate system; we then incorporated these data into a hybrid coupled ocean-atmosphere model (HCM) to quantify its effects on ENSO. A new mechanism was revealed by which interannual FWF forcing modulates ENSO in a significant way. As a direct forcing, FWF exerts a significant influence on the ocean through sea surface salinity (SSS) and buoyancy flux ( Q) in the western-central tropical Pacific. The SSS perturbations directly induced by ENSO-related interannual FWF variability affect the stability and mixing in the upper ocean. At the same time, the ENSO-induced FWF has a compensating effect on heat flux, acting to reduce interannual Q variability during ENSO cycles. These FWF-induced processes in the ocean tend to modulate the vertical mixing and entrainment in the upper ocean, enhancing cooling during La Niña and enhancing warming during El Niño, respectively. The interannual FWF forcing-induced positive feedback acts to enhance ENSO amplitude and lengthen its time scales in the tropical Pacific coupled climate system. [ABSTRACT FROM AUTHOR]

The mean of the sea level deviation data derived from the TOPEX/Poseidon altimeter in the equatorial Pacific, between 10&degS and 10&degN, and between 120&degE and 78&degW, from cycles 2 to 136 (3 October 1992--2 June 1996), are extracted using a maximum-minimum average method. Then, two-dimensional (2D) sea level deviation time series are developed to visualize the dynamics of equatorial waves. The complex singular value decomposition (CSVD) method is applied to decompose these 2D time series into empirical orthogonal modes. Using this method, zonal and meridional structures, propagation directions, periods, and propagation speeds of these empirical modes are obtained. The first empirical mode is propagating westward, and its structure is asymmetric to the equator. It has an average phase speed c= -0.6 m s[sup-1] within 4&deg--6&degN and c= -0.4 m s[sup-1] within 6&deg--8&degS, respectively, and a period of 15 months, which is associated with an interannual Rossby wave. The second empirical mode is propagating eastward along the equator and has a phase speed of 2.5 m s[sup-1] and a period of 7 months, which is associated with an equatorial Kelvin wave. The asymmetric feature of the empirical Rossby wave, which is also observed in the equatorial Pacific, may suggest that the background currents and wind fields in the equatorial Pacific Ocean affect its propagation. The amplitude of the empirical Kelvin mode increases as it propagates eastward. This is associated with an eastward shoaling of the thermocline depth along the equatorial Pacific Ocean. The results of both empirical modes are consistent with those predicted by the theory of Kelvin and Rossby waves and closely represent the actual features of both waves observed in the equatorial Pacific Ocean. Therefore, the CSVD is a suitable method for revealing the dynamics of equatorial waves. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we investigate the temperature and size variability of the areas with sea surface temperature (SST) higher than 20°C in the global oceans. The SST and surface heat flux data from 1982 to 2008 are used as a baseline. The SST in the global oceans is binned into 1°C interval. Observations at the warm pools (SST>29°C) show larger area increase rates than that in lower SST areas because the net heat flux accumulates enough energy to support the development of SST in warm pools. Furthermore analyses of upper ocean heat budget between heat advection and heat diffusion suggest that heat diffusion processes may be a mechanism for transporting excessive amount of heat that the warm pool through enhancing the SST gradient around the edge of the warm pool. In the Pacific and the Atlantic, the warm pools have a maximum increase rate of 60% of their original area. The area increase rate between 29°C and 30°C in the global oceans is as high as 51% of area. An ensemble empirical mode decomposition analysis shows that the interannual component has strong influence on the variability of the warm pool in the Pacific, presumably because of the presence of El Nino-Southern Oscillation, while the annual cycle dominates the variability in the Atlantic and the Indian Ocean. [Copyright &y& Elsevier]