Sea-level variability in the Caribbean Sea over the last century

Mean sea level rise exposes coasts to increasing risks. For the Caribbean Sea, the regional and local sea-level behaviour is not well known. This study has investigated the sea level behavior in the region at different frequencies during the last century, to provide updated, accurate and useful information to implement coastal adaptation responses to sea-level hazards. Time series from 28 tide-gauges, 18 years of altimetry and various atmospheric and oceanographic climatologies have been used. Several new results have been found. The small Caribbean tides have significant long-term modulations. The net effect of the low frequency modulation of the tidal signal can change the maximum tidal range up to 23.5%. The seasonal sea level cycle is characterized by large spatial and temporal variability. The amplitude of the coastal annual harmonic ranges from 2 cm to 9 cm, peaking between August and October. The amplitude of the semi-annual harmonic has maximum amplitude of 6 cm but it is not significant at all stations. The barometric effect dominates the coastal semi-annual cycle, but it is insignificant in all the other sea level frequencies at the tide-gauges. The seasonal sea level cycle from altimetry confirms the results obtained from the tide-gauges and allows the identification of some dominant sea level forcing parameters such as the Panama-Colombia gyre driven by the wind stress curl and the Caribbean Low Level Jet modulating the sea level in the northern coast of South America and linked to the local upwelling. The basin average mean sea level rise from altimetry is 1.7±1.3 mm yr-1 for the period 1993-2010. Wind forcing changes causes the trends in the southern part of the basin, modulating the sea level through changes in the ocean circulation. Significant spatial and decadal variability of the trends is found. Secular coastal sea-level trends range from 1.3±0.2 mm yr-1 in Magueyes, where the steric contribution dominates, to 5.3±0.3 mm yr-1 in Cartagena, where other contributors including local vertical land movements are significant. Temporal changes in the sea level extremes are significant but in line with mean sea-level trends at each tide gauge. With the annual mean sea level removed, extremes range between 36 cm and 79 cm, the later recorded in Port Spain and caused by the largest tidal signal. The largest nontidal residual is 76 cm found in Magueyes, forced by a hurricane induced storm surge, however larger surges can occur in the basin. The interannual sea level signal and nontidal extremes correlate with El Nino-Southern Oscillation at different time and spatial scales. No correlation with the North Atlantic Oscillation is found at any frequency. The largest sea flooding probability in the Caribbean coasts is around October, when the different sea level contributors’ maximums interact. These sea flooding events are going to became more frequent in the future due to the secular mean sea level rise affecting the basin.