WAVELET ANALYSIS OF LATE HOLOCENE STALAGMITERECORDS FROM ORTIGOSA CAVES IN NORTHERN SPAIN

摘要

We have deduced short-term climatic changes from millennial to annualscales from the study of laminae thickness and radiocarbon analysis of Holocenestalagmite records from two caves in Ortigosa de Cameros (Iberian Range, northernSpain). Speleothems are made up of dark compact laminae (DCL) and white porouslaminae (WPL) of seasonal origin. Couplets seasonality is deduced from monitoringcalcite laminae growth, drip water rates, and soil organic matter flushed into the caves.The thickness variations of the couplets are analyzed using a continuous wavelettransform and the various periodicities at interannual, decadal, multidecadal, andcentennial scales are revealed from the wavelet power spectrum. The periodicities atdecadal, multidecadal and centennial scales, with periods around 9.7, 10.4, 14, 16, 22, 43,73, 83 and 180 years, are mainly related to solar activity. Among the interannualperiodicities, oscillations around the 2.4-yr-period may be linked to the Quasi-BiennialOscillation (QBO), whereas periods ranging from 4 to 7 years may be associated with theEl Nino-Southern Oscillation (ENSO) and/or the North Atlantic Oscillation (NAO).