DRIVERS OF SEA LEVEL VARIATIONS ALONG THE NORTHERN COAST OF BAY OF BENGAL: STATISTICAL ANALYSIS OF TEMPERATURE, SALINITY, WIND STRESS, AND REGIONAL CLIMATIC FACTORS

Despite being a low contributor to global warming, Bangladesh is one of countries most vulnerable to sea level (SL) rise. In this study, by utilizing empirical orthogonal function analysis, an attempt was made to investigate how the regional oceanic (sea-surface temperature, sea-surface salinity) and atmospheric (air temperature, wind stress curl, and precipitation) factors, as well as the regional climate variability are linked with the seasonal and annual variations of recent SL along the northern Bay of Bengal. Besides, geomorphological factors that may have contributions to SL along this coast were also analyzed from literatures. This study suggests that the recent annual trend of SL ranges from 3.23 mmy^-1 to 11.76 mmy^-1 based on tide gauge data and 3.6 mmy^-1 based on AVISO altimetry data. The SL shows a strong seasonal variation as such it is lowest in the winter but high from June to November. This seasonal variation shows strong positive correlations with sea surface salinity indicating salinity as a major controlling factors. The long-term SL trend is well-correlated with the increasing trend of sea surface temperature. Whereas, the long-term trend of increasing salinity and positive wind stress curl negatively correlated with SL change. Additionally, SL is low during the combined events of positive IOD and El Niño both, whereas it is high during the combined events of negative IOD and La Niña. Reduced sedimentation and accumulation rate in recent time, and persistent subsidence also let this coast exposed to SL rise and eventually, high tide flooding and salinity-intrusion leave the coastal community to a potential vulnerable position. Numerical model study can be done in future to quantify the role of salinity and wind stress curl in changing the SL in this bay, and present study would be a base line.