The global and persistent millennial-scale variability in the thermoluminescence profiles of shallow and deep Mediterranean sea cores

In this paper we present the thermoluminescence (TL) profile in the last 7500 y, measured in the upper part of the deep Tyrrhenian sea core CT85-5. This core was dated with tephroanalysis and radiocarbon techniques: a constant sedimentation rate (10 cm/ky) was found up to 200 cm. The sampling interval adopted for obtaining the TL profile is 2.5 mm, corresponding to 25 y. Using different spectral-analysis methods, we show the presence of a millennial-scale variability, corresponding to an average period of about 1315 y. This oscillation has been noted also in other climatic indices measured in North Atlantic sea sediment cores and in the Greenland GISP2 ice core. This result indicates that this millennial oscillation is the expression of climate changes of worldwide extent. We show that this millennial periodicity persisted during the last deglaciation. The transition to Holocene was determined in our core by the oxygen isotope ratio d 18O measured in Globigerina bulloides. The fact that the observed TL changes do not have a local character is also suggested by the excellent agreement between this deep sea TL profile of the uppermost part of the core and the TL profile measured in the shallow Ionian sea GT89-3 core over the last 2500 y, with a time resolution of 3.096 y

The sunspot cycle recorded in the thermoluminescence profile of the GT89/3 Ionian sea core

We measured the thermoluminescence (TL) depth profile of the GT89O3 shallow-water Ionian sea core. This profile has been transformed into a time series using the accurate sedimentation rate previously determined by radiometric and tephroanalysis methods. The TL measurements were performed in samples of equal thickness of 2 mm, corresponding to a time interval of 3.096 y. The TL time series spans A1800 y. The DFT power spectral densities in the decadal periodicity range of this TL series show significant periodicities at 10.7, 11.3 and 12 y closely similar to the periodicities present in the sunspot number series. These results confirm that the TL signal in recent sea sediments faithfully records the solar variability, as we previously proposed

22 year cycle in the planktonic 18 of a shallow-water Ionian sea core

The d18 O profile of Globigerinoides ruber was measured in the GT90/3 Ionian sea core between 1205 and 1898 AD. The high temporal resolution of 3.87 y allowed us to determine the presence in the time series of an 11 y component with an amplitude of 0.07‰, at significance level of 99% (by Monte Carlo singular spectrum analysis, MC-SSA). Here we focus attention on the 22 y periodicity in the time series and we show that SSA principal components (PCs) 15 and 16 carry this oscillation, in phase with the Hale solar cycle, obtained by inverting the odd cycles of the sunspot number series. This result shows that the even and odd Schwabe cycles do not have the same influence on this climatic record

Cosmic ray secular variations in terrestrial records and aurorae

The rediscovery that the Sun and the solar wind can undergo important changes on historical time scales has brought into question the stability of the cyclic behavior of past time series of solar and solar-terrestrial origin. It was found by Vector Fourier analysis that the solar 11 year cycle is present in the series of 10Be, delta 180, in ice cores and of thermoluminescence (TL) in sea sediments during the last Millennia with a frequency modulation, related to the Sun behavior, as tested by comparison with the Sunspot number R sub z series. It was shown that the cyclogram of the series of yearly Aurorae from 1721 to 1979 linear-regression-corrected-for-R sub z is straight for the periodicity zeta=11,1y, which indicates that such periodicity is constant in time corresponding to the only line present in the 11y band. The maxima of this component appear at the same time together with the high speed solar wind streams taking place in coronal holes situated in high heliolatitudes. It is evidenced that the 11 year cycle has undergone frequency oscillations on a time scale of two centuries, although it is very difficult to determine the periodicities with high accuracy

Cosmic rays 10Be biennal data and their relationship to aurorae and sunspots

The galactic cosmic ray (C.R.) variations which should give information on three dimensional aspects of the heliospheric magnetic fields and on the solar wind, which modulate their influx into the Solar System were studied. In order to decode the information from the C.R. series it is necessary to know the mechanisms through which the modulation is produced. It it clear that a balance of effects with sources at different heliospheric latitudes results in the modulated C.R. intensity. It is found that the modulation of 10Be in polar ice may be due to at least two main contributions: (1) negative and in phase with the Solar flare activity modulating the cosmic ray flux in Forbush-type decreases, and (2) positive in phase with the appearance of large wind streams situated at both polar coronal holes. It is found that the high heliolatitude activity is related to a stable periodicity of 11.1y whereas the low heliolatitude activity contributes to the wondering of the solar cycles

On the half-life of 44Ti by results in meteorites

Measurements of the 44Ti half-life display a large spread ranging from 46.4 to 66.6 years. The activity of this radioisotope measured in eight meteorites (chondrites) fell in the time interval 1883-1992 and calculated at the time of fall by the different values of T1O2 shows that the shorter values are not reliable, if it is assumed that the average cosmic-ray intensity has remained the same during the past two centuries. The low activity of the cosmogenic isotope 44Ti has been determined by means of a selective Ge-NaI (Tl) g-spectrometer with a very low background (about 1 count per day in the g-peak at 1157 keV of 44Sc in equilibrium with its parent 44Ti). The high stability of this system allows long-lasting runs (A107 s ), in order to achieve the standard deviation of counting up to A10%. PACS 94.40.Vf – Cosmic-ray effects in meteorites and terrestrial matter

Cosmogenic isotopes and geomagnetic signals in a Mediterranean sea sediment at 35000 y BP

In this paper we present the results on the relative changes of the geomagnetic field intensity measured in the Tyrrhenian sea core CT85-5 between 23 and 51 ky BP in order to investigate the origin of the enhancement of the cosmogenic isotope 10Be concentration, recently reported in the same core at 35 ky BP