Search

Climatic signals were extracted from ring-width chronologies of Scots pines (Pinus sylvestris L.) from natural stands of the northern, middle, and southern parts of the boreal forest belt in Finland. The strength of the common growth signals (forcing factors) were quantified as a function of time. This was achieved by mean inter-series correlations, calculated over a moving 30-year window, both within and between the regional chronologies. Strong regional signals and also evidence for common forcings were found, especially between northern and central, central and eastern, as well as central/eastern and southern chronologies. Response function analyses revealed that growing season temperatures govern the growth rates of northern pines, while towards south, pine growth becomes less affected by temperatures, and more affected by e.g. precipitation. During some periods, growing conditions seem to have been favorable in the south, while they have been unfavorable in the north (growth inversions). Going from the north to the south, the variability of radial growth clearly decreases, and the variance of ring-width series becomes smaller. Growth variability in the four regions was compared during the common interval of the chronologies, from 1806 to 1991. The spectral densities of the northern, central, eastern and southern chronologies were also compared as functions of frequency, viz. cycles per year. The variance is much greater and there is more periodic behavior in the north than in the south in high, medium, as well as lower frequencies.

A comparison was performed of solar activity and terrestrial temperature records, both derived from tree rings (i.e., without dating uncertainties), with identification of detailed and highly quantified time- and time-scale-dependent characteristics of solar forcing on climate through the current interglacial in the context of oceanic variability. The tree-ring-derived temperature record from high latitudes of Europe (Lapland) exhibits persistent annual-to-millennial--scale variations, with multidecadal to multicentennial periodicities reminiscent of the Sun's periodicities. At millennial scales, cool temperatures coincided with large-scale glacial maxima. Moreover, millennial and bimillennial modes of climate variability were correlative with variations in sunspot numbers on similar scales, with near-century and near-zero lags, respectively. Although they were subtle in amplitude, the sub-Milankovitch--scale changes in the reception of the Sun's energy could thus suffice to noticeably modulate interglacial climate variations. The relative significance of timescale-dependent, Sun-climate linkages has likely varied during the mid and late Holocene times, respectively. Thus, the warmer and cooler paleotemperatures during the Medieval Climate Anomaly and Little Ice Age were better explained by solar variations on a millennial rather than bimillennial scale. The observed variations may have occurred in association with internal climate amplification (likely, thermohaline circulation and El Nino--Southern Oscillation activity). The near-centennial delay in climate in responding to sunspots indicates that the Sun's in fluence on climate arising from the current episode of high sunspot numbers may not yet have manifested itself fully in climate trends. If neglected in climate models, this lag could cause an underestimation of twenty-first-century warming trends. doi: 10.1130/B30088.1

The Holocene land/sea-level changes in Finnmark, North Norway, were determined with the help of radiocarbon dates of shells from raised beaches. The regression of the sea level below 25 m could be dated in the Varangerfjord area for the time interval 5500–3600 B.P:, and below 15 m for the outer coast of the Varanger peninsula after about 4500 B.P. In addition, dates from two lakes and a former dated peat at Tomaselv were used to determine the lowering of the sea level after 9000 B.P. It was shown that radiocarbon dates of charcoal samples from archaeological sites cannot directly be compared with the other dates and also that lichenometry cannot be used in the study of the Iand/sea-level changes of the area. The influence of corrected radiocarbon ages is also discussed. [ABSTRACT FROM PUBLISHER]