Mean Sea Level Trends Based on Tide Gauge Records and Their Possible Morphological Effects on the Coastline of Southern Rio de Janeiro (SE Brazil)

The present work analyzes mean sea level (MSL) measurements recorded by a tide gauge installed at Ilha Fiscal (Guanabara Bay, Rio de Janeiro, SE Brazil). For this purpose, a time series spanning 54 years (1963–2017) was processed and filtered for one (yearly averages), four, and twelve (monthly averages) elements per year. In addition, possible climate teleconnections were verified through the SOI, TSA, and AMM indices for the same period, resulting in non-existent or weak correlations. MSL trends were calculated using first, second, and third-degree polynomials. Sea level projections for 2100 were compared with scenarios proposed by the Intergovernmental Panel on Climate Change (IPCC). The lowest MSL rising rate, 2.42 mm/year, was determined through linear regression (first-degree polynomial), with a slight deceleration from 1989 to 2016 (1.93 mm/year). The contours of possible future coastlines of the southern Rio de Janeiro area were drawn, illustrating the implications of shoreline retreat ranging between ~ 40 and ~ 500 m by 2100. In general, the projection for the end of this century points to relevant impacts on the studied area, including breaching the Marambaia barrier island central sector, where an opening as wide as 12–14 km could develop.