Mid- to Late-Holocene Mediterranean climate variability: Contribution of multi-proxy and multi-sequence comparison using wavelet spectral analysis in the northwestern Mediterranean basin

Forcing and mechanisms underlying Holocene climate variability still remain poorly understood. This work review already published paleoclimatic time series and proposes an alternative way to compare them using spectral analysis. Such an approach may emphasize joint features between different signals and lead us closer to the causes of past climate changes. Seven paleoclimatic proxy records from 2 sequences from the Gulf of Lion were compiled. These paleoclimate time-series were supplemented with proxies of the Atlantic area, the solar activity and a sequence recording El Nino-Southern Oscillations (ENSO) past variability. A comparison of their frequency content is proposed using wavelet spectral analysis for unevenly sampled time series. A new algorithm is used in order to propagate the age model errors within wavelet power spectra. Two main groups of shared spectral features specific to the Mid- and Late Holocene (after 8200 yrs. cal BP) can be defined on the basis of the results of these analyses, an Atlantic spectral feature (similar to 1500 yrs) and two possible tropical Pacific spectral features (600-700 and 2000-2200 yrs). The Atlantic cyclic period is probably related to fluctuations of the Atlantic thermohaline circulation which would induce changes in the storm track extension and position thereby impacting upon precipitation and storminess over a millennial scale. The ENSO variability spectral features which are registered in the Gulf of Lion proxies, potentially highlight a possible link between the tropical Pacific and the western Mediterranean climates during the Mid to late Holocene that needs to be further investigated.