Sea Level Variability in the West Coast of Sri Lanka

Abstract

Sea level variability in west cost of Sri Lankan waters was investigated by means of insitu (Tide gauge) and satellite altimetry data over a period spanning two decades from 1993 to 2014. This paper describes the sea level variations during the mentioned time period retrieved from the two data sets. The gauge data were used from the global network of Inter-Gaovernmental Oceanographic Commision (IOC)and Achiving, Validation and Interpritation of Satellite Oceanographic (AVISO)sattelite data. Mean sea level (MSL) estimates obtained from tide gauge data showed root mean square differences (RMSDs) were approximately 80% of the variance of the MSL signal estimated from satellite altimetry data. Considering the individual time series, the results showed that coastal tide gauge and satellite sea level signals are comparable, with RMSDs less than 4cm and correlation coefficients up to the order of 0.9. Positive sea level linear trend for the analysis period were estimated for both the mean sea level and the coastal stations. From 1993 to 2014, the mean sea-level trend (1.9824 mm/ year) was found to be affected by the positive anomalies of 2008 and 2014, which were observed in all the cases analysed and were mainly distributed in coast of the western and southern Sri Lanka. Analysis of climatology salinity and temperature field and model outputs, it was evident that change in steric sea level (or dynamic height) is the main factor leading to seasonal MSL change and trend. Ensemble empirical mode decomposition showed that inter-annual variability was related to the processes that have dominant periodicities of 4-6 years related to El Nino Southern Oscillation (ENSO) events. In terms of mean sea level trends, a significant positive sea level trend (>>95%) was found on the basis of at least 10 years of data.