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Abstract. Extreme ocean waves in the Caribbean

Abstract. The aim of this study is to determine the contribution and importance of cold fronts and storms to extreme waves in different areas of the Colombian Caribbean in an attempt to determine the extent of the threat posed by the flood processes to which these coastal populations are exposed. Furthermore, the study wishes to establish the actions to which coastal engineering constructions should be subject. In the calculation of maritime constructions, the most important parameter is the height of the wave. For this reason, it is necessary to establish the design wave height to which a coastal engineering structure should be resistant. This wave height varies according to the return period considered. The significant height values for the areas focused on in the study were calculated in accordance with Gumbel's extreme value methodology. The methodology was evaluated using data from the reanalysis of the spectral National Oceanic and Atmospheric Administration (NOAA) WAVEWATCH III® (WW3) model for 15 points along the 1600 km of the Colombian Caribbean coastline (continental and insular) between the years 1979 and 2009. The results demonstrated that the extreme waves caused by tropical cyclones and those caused by cold fronts have different effects along the Colombian Caribbean coast. Storms and hurricanes are of greater importance in the Guajira Peninsula (Alta Guajira). In the central area (consisting of Baja Guajira, and the cities of Santa Marta, Barranquilla, and Cartagena), the strong impact of cold fronts on extreme waves is evident. However, in the southern region of the Colombian Caribbean coast (ranging from the Gulf of Morrosquillo to the Gulf of Urabá), the extreme values of wave heights are lower than in the previously mentioned regions, despite being dominated mainly by the passage of cold fronts. Extreme waves in the San Andrés and Providencia insular region present a different dynamic from that in the continental area due to their geographic location. The wave heights in the extreme regime are similar in magnitude to those found in Alta Guajira, but the extreme waves associated with the passage of cold fronts in this region have lower return periods than those associated with the hurricane season.

ResumenSe analizaron series mensuales del transporte de sedimento en suspensión de siete ríos del Caribe colombiano, con el fin de proporcionar un estimativo actualizado, detectar los cambios recientes y los patrones de variabilidad del transporte de sedimento en suspensión. En su conjunto, estos ríos transportan un promedio de ~146,3 x10 6 t a -1 de sedimentos en suspensión hacia el litoral Caribe colombiano. El mayor aporte proviene del río Magdalena, con 142,6 x10 6 t a -1 , que corresponden a 38 % del total de los sedimentos en suspensión estimados para el litoral Caribe. La tasa anual del transporte de sedimentos en suspensión de estos sistemas fluviales ascendió hasta 36 % entre 2000 y 2010. El análisis espectral basado en la transformada de ondícula (wavelet) evidenció lapsos de intensa variabilidad entre los periodos 1987-1990 y 1994-2002, en los cuales las principales componentes oscilatorias aparecieron de manera simultánea. Las bandas anual, semianual y 'cuasi-decadal' aparecieron como las principales componentes oscilatorias en la variabilidad del transporte de sedimento en suspensión, mientras que las bandas 'cuasibienal' e interanual constituyeron una fuente de variabilidad de segundo orden. Se considera que los mecanismos forzadores climáticos y oceanográficos asociados con las oscilaciones detectadas mediante el análisis espectral definen un marco de variabilidad de mediano a largo plazo para el transporte de sedimentos en suspensión.Palabras clave: transporte de sedimentos en suspensión, mar Caribe, variabilidad hidrológica, análisis espectral basado en la transformada de ondícula. Suspended sediment load in Colombian Caribbean Rivers: Magnitude, trends and variability AbstractThe data on the monthly average of suspended sediment load from seven rivers in northern Colombia (Caribbean alluvial plain) draining into the Caribbean Sea were analysed to quantify the magnitudes, to estimate long-term trends, and to evaluate the variability patterns. These rivers deliver an average of ~146.3 x10 6 t yr -1 of suspended sediments to the Colombian Caribbean littoral. The largest sediment supply is provided by the Magdalena River, with a mean suspended sediment load of 142.6 x10 6 t yr -1 , which is 38% of the total fluvial discharge estimated for the Caribbean littoral. Between 2000 and 2010, the annual suspended sediment load of these rivers increased to 36%. The wavelet spectral analyses highlighted periods of intense variability between the periods of 1987-1990 and 1994-2002, where the major oscillation processes appeared simultaneously. The semi-annual, annual and quasi-decadal bands were the main factors controlling the suspended sediment load variability of these fluvial systems, whereas the quasi-biennial and interannual bands constituted second order sources of variability. The climatic/oceanographic drivers associated to the oscillations identified through the wavelet spectral analyses defined a medium/long term framework of variability for the suspended sediment load.

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