Extreme storms during the last 6,500 years from lagoonal sedimentary archives in Mar Menor (SE SPAIN)

Amongst the most devastating marine catastrophes that can occur in coastal areas, are storms and tsunamis, which may seriously endanger human society. Many such events are known and have been reported for the Mediterranean, a region where high-frequency occurrences of these extreme events coincides with some of the most densely populated coastal areas in the world. In a sediment core from Mar Menor Lagoon (SE Spain), we discovered eight coarse grained layers which document marine incursions during periods of intense storm activity or tsunami events. Based on radiocarbon dating, these extreme events occurred around 5250, 4000, 3600, 3010, 2300, 1350, 650 and 80 years cal B.P.. No comparable events have been observed during the 20th and 21th centuries. The results indicate little likehood of a tsunami origin for these coarse grained layers, although historical tsunami events are recorded in this region. These periods of surge events seem to coincide with the coldest periods in Europe during the late Holocene, suggesting a control by a climatic mechanism for periods of increased storm activity. Spectral analyses performed on the sand % revealed four major periodicities of 1228 ±327, 732 ±80, 562 ±58, and 319 ±16 yr. Amongst the well-known proxies that have revealed a millennial-scale climate variability during the Holocene, the ice-rafted debris (IRD) indices in North Atlantic developed by Bond et al. (1997, 2001) present a cyclicity of 1470 ±500 yr, which matches the 1228 ±327 yr periodicity evidenced in the Mar Menor lagoon, considering the respective uncertainties on the periodicities. Thus, an in-phase storm activity in Western Mediterranean is found with the coldest periods in Europe and to the North Atlantic thermohaline circulation. However, further investigations, such as additional coring, high-resolution coastal imagery, are needed to better constrain the main cause of these multiple-events.