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02 février 2017
Extreme storms during the last 6500 years from lagoonal sedimentary archives in the Mar Menor (SE Spain)
Extreme storms during the last 6500 years from lagoonal sedimentary archives in the Mar Menor (SE Spain)

Fig. 1. Grain  size  population  from  the  Mar  Menor  MM2record with clay (< 2 μm), silt (> 2 and < 63 μm), and sand fraction (> 63 μm). Shaded areas mark the main variations of the sand fraction.

Storms and tsunamis, which may seriously endanger  human  society,  are  amongst  the  most  devastating  marine catastrophes that can occur in coastal areas. 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 the Mar Menor (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 BP. No comparable events have been observed during the 20thand  21st  centuries.  The  results  indicate  little  likelihood  ofa  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  acontrol  by  a  climatic  mechanism  for  periods  of  increased storm activity. Spectral analyses performed on the sand percentage  revealed  four  major  periodicities  of  1228±327, 732±80, 562±58, and 319±16 years.


Amongst the wellknown proxies that have revealed a millennial-scale climate variability during the Holocene, the ice-rafted debris (IRD) indices in the North Atlantic developed by Bond et al. (1997, 2001) present a cyclicity of 1470±500 years, which matchesthe 1228±327-year periodicity evidenced in the Mar Menor, considering the respective uncertainties in the periodicities. Thus,  an  in-phase  storm  activity  in  the  western  Mediterranean  is  found  with  the  coldest  periods  in  Europe  and with the North Atlantic thermohaline circulation. However, further  investigations,  such  as  additional  coring  and  high-resolution coastal imagery, are needed to better constrain the main cause of these multiple events.

L. Dezileau, A. Pérez-Ruzafa, P. Blanchemanche, J-P. Degeai, O.Raji, et al.

Reference :  Clim. Past, 12, 1389–1400, 2016

#102 - Màj : 16/03/2017
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