Effects of Climate Variability on the Morphodynamics of Uruguayan Sandy Beaches
Effects of long-term trends in climatic variability on the morphodynamics of a reflective and a dissipative sandy beach in Uruguay (SW Atlantic Ocean) were analyzed. The Atlantic Multidecadal Oscillation (AMO) alternates between warm and cold cycles with a periodicity of roughly 70 years, with a shift toward a warm phase since 1995, resulting in an increase of sea surface temperature in the study area. Wind speed anomalies (WSA) also increased through time and were associated with an increasing speed of southerly winds, particularly after 1997. Beach morphodynamics showed no statistically significant trends in grain size, but long-term morphodynamic patterns differed between beaches: the dissipative beach showed an increase in swash and beach width, Dean's parameter, and the Beach Index (a measure of beach morphodynamic state). At the same time, the slope decreased, augmenting the beach's dissipative characteristics. The reflective beach showed an increase in slope and swash width through time, and a decrease in the Beach Index, indicating an intensification of reflective characteristics. Long-term morphodynamic changes were more evident in the dissipative beach and related to climate forcing (e.g. WSA). A higher resilience was observed in the reflective beach, even though an increasing frequency of storms is affecting both beaches. Accelerating erosion, rising sea levels, and expanding urban development in the Uruguayan coast could affect biodiversity and critical habitats. Multidisciplinary investigation programs and conservation strategies are needed to mitigate negative anthropogenic effects on these ecosystems.