Study of climatic series by time-frequency analysis

Abstract

CEPHAG, BP 46 -38402 SAINT MARTIN DHERES

High‐frequency paleovariability in climate and CO2 levels from Vostok Ice Core Records

“…Of these tones we note the second harmonic of an orbital peak, 2f2, and the third harmonic, at 3.5 kyr, of 10.4 kyr = 1/(f• + f2), particularly prominent in the GLT results [Le Treut and Ghil, 1983;Ghil, 1985;Le Treut et al, 1988]. The well-known ice core peak near 2.5 kyr [Dansgaard et al, 1971;Benoist et al, 1982] appears to split into two sharp peaks, near 2.7 and 2.4 kyr. Pestiaux et al [1988] had also detected two combination tones near 2.5 kyr in their marine cores, but their respective orders were both 9, rather than 8, confirming the better resolution of the Vostok record and the sharper discrimination of our spectral methods.…”

“…These interactions may act in turn through both global albedo and sea level changes[Peltier, 1982] on equatorial sea surface temperature[Pisias and Rea, 1988] and on atmospheric CO2 levels[Barnola et al, 1987].The presence of frequencies higher than the orbital ones in both the GLT model and the Vostok temperature record suggests pushing the investigation toward still higher frequencies. In particular, it is well known from previous studies of ice cores from Greenland[Dansgaard et al, 1971] and from other parts of Antarctica[Benoist et al, 1982] that a peak near 2.5 kyr is quite prominent in •80 records from the ice. Hence we consider in Figure 3 frequencies between 0.1 and 0.65 cycles/kyr.…”

Paleoclimatic variability at frequencies ranging from 1 cycle per 10 000 years to 1 cycle per 1000 years: Evidence for nonlinear behaviour of the climate system

“…Denton and Karlen (1973) found a near-periodicity of 2.5 kyr in the postglacial waxing and waning of North American and European mountain glaciers. Dansgaard et al (1984) and Benoist et al (1982) found periodicities around 2.5 kyr in oxygen isotopic records from Greenland and Antarctic ice cores, respectively.…”