Seasonal variation of eddy activity and associated heat/salt transport in the Bay of Bengal based on satellite, Argo and 3D reprocessed data

Abstract

Abstract. Based on satellite altimetry data spanning over 26 years in combination with Argo profile data or three‐dimensional (3D) reprocessed thermohaline fields, the eddy synthesis method was used to construct vertical temperature and salinity structures of eddies in the Bay of Bengal, and the seasonal thermohaline properties of eddies and the heat and salt transport by eddies were analyzed. Analysis revealed that mesoscale eddy activity in the Bay of Bengal has evident seasonal variation, which has notable impact on the circulation system within the entire bay. Temperature anomalies caused by eddies are usually between ±1 °C and ±3 °C, positive for anticycloic eddies (AEs) and negative for cyclonic eddies (CEs), and the magnitude varies seasonally. Salinity anomalies caused by eddies are small and disturbance signals in the southern bay due to the small vertical gradient of salinity there; salinity anomalies in the northern bay are generally between ±0.2 psu and ±0.3 psu, negative for AEs and positive for CEs. Owing to obvious seasonal changes of both the eddy activity and the vertical thermohaline structure in the Bay of Bengal, the eddy-induced heat and salt transport in different seasons also changes substantially. Generally, high heat and salt transport is concentrated in eddy-rich regions, e.g., the western, northwestern and eastern parts of the bay, the seas to the east of Sri Lanka, and the region to the southeast outside of the bay. The southern part of the bay shows weak freshwater transport owing to the inconsistent salinity signal within eddies. The seasonal ZHT of CEs and AEs in the whole bay is in the order of 10×1012 W, with higher values in autumn and winter and smaller values in spring and summer. The seasonal ZWT of CEs is generally larger than that of AEs, thus the ZWT of all eddies is eastward with high values (> 5×103 m3·s-1) in summer and autumn. By contrast, the seasonal MHT and MWT in the whole bay is relatively small, mostly below 1×1012 W and 2×103 m3·s-1, respectively. This work provides data that could support further research on the heat and salt balance of the entire Bay of Bengal.