An ocean reanalysis that covers the period from 1871 to 2008 is used to analyze the interannual variability of sea surface salinity (SSS) in the tropical Indian Ocean. The reanalysis SSS and the SSS anomaly patterns during Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO) events are compared with patterns from Argo SSS data. The mean seasonal SSS variation is large in the northern Bay of Bengal compared with variations in the Arabian Sea and equatorial Indian Ocean. During a positive IOD event, positive SSS anomalies are found along the Sumatra coast that are due to the combination of wind‐driven upwelling of subsurface high‐salinity waters, enhanced evaporation, and anomalous surface circulation. The opposite is true, to a lesser extent, during negative IOD events. A dipole mode index for salinity (DMIS) based on SSS data and a new index based on the average of salinity in a region off the coast of Sumatra are introduced to monitor SSS variability during IOD and ENSO events. The impact of concomitant El Niño events on a positive IOD event is large with freshening (a negative SSS anomaly) in the equatorial Indian Ocean and salting (positive SSS anomaly) off the southern Sumatra coast. The (impact of) intense freshening reaches into the southwestern tropical Indian Ocean. The impact of concomitant La Niña with negative IOD is also large with an intense freshening in the southeastern Arabian Sea and salting off the northern Sumatra coast.
[1] The Madden-Julian Oscillation (MJO) impacts a wide range of weather and climate phenomena. Current global coupled ocean-atmospheric general circulation models exhibit considerable shortcomings in representing and predicting the MJO, specifically its initiation, due to a lack of in situ observations. Here we show, for the first time, that the MJO propagation can be detected from the newly launched NASA Aquarius Salinity mission. The magnitude and extent of sea surface salinity (SSS) variations during the MJO is established, providing a useful tool for data assimilation into models to correctly represent both oceanic and atmospheric processes during intraseasonal variations. Salinity observation allows for atmospheric conditions to be inferred from freshwater flux, on which surface salinity is highly dependent. Increased observations of global SSS from the Aquarius mission will be particularly valuable in remote regions of the tropics and will increase our dynamical understanding and advance prediction of the MJO through model improvement.
Using satellite measurements of Outgoing Longwave Radiation (OLR) and Simple Ocean Data Assimilation (SODA) reanalysis, the Madden‐Julian Oscillation (MJO) influence on Sea Surface Salinity (SSS) across the Indian Ocean is examined. The SSS pattern during different stages of the MJO propagation across the Indian Ocean are analyzed conditioned on season and phase of the El Niño – Southern Oscillation. The processes through which the SSS patterns develop depend upon anomalous atmospheric conditions and oceanic processes during the different stages of the MJO. The combinations of anomalous conditions during each stage of the MJO with seasonal and long‐term climate variations create different responses in SSS. The SSS variability during the MJO may produce numerous indirect feedbacks, which are the result of SSS altering the depth of the Barrier Layer (BL) and mixed layer. Satellite salinity measurements will enhance our knowledge of the SSS variability during different stages of the MJO propagation.
The fluctuation of Arctic sea ice concentration (SIC) has been associated with changes in ocean circulation, ecology, and Northern Hemisphere climate. Prediction of sea ice melting patterns is of great societal interest, but such prediction remains difficult because the factors controlling year-to-year sea ice variability remain unresolved. Distinct monsoon–Arctic teleconnections modulate summer Arctic SIC largely by changing wind-forced sea ice transport. East Asian monsoon rainfall produces a northward-propagating meridional Rossby wave train extending into the Siberian Arctic. The Indian summer monsoon excites an eastward-propagating circumglobal teleconnection along the subtropical jet, reaching the North Atlantic before bifurcating into the Arctic. The remote Asian monsoon variations induce a dominant dipole sea ice melt pattern in which the North Atlantic–European Arctic contrasts with the Siberian–North American Arctic. The monsoon-related sea ice variations are complementary and comparable in magnitude to locally forced Arctic Oscillation variability. The monsoon–Arctic link will improve seasonal prediction of summer Arctic sea ice and possibly explain long-term sea ice trends associated with the projected increase in Asian monsoon rainfall over the next century.
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