ИСТИНА

The Sun's role in climate variability is now a subject of debates, especially in the context of understanding contribution of solar forcing to modern global warming. Besides, there are some evidences of the approaching new Grand Solar Minimum with Little Ice Age climatic conditions (K.G. McCracken and J. Beer, JGR, 119, 2379-2387, 2014; N.-A. Morner, Natural Science, 7, 510-518, 2015). This expectation is based on the occurrence of the extended solar minimum of 2006-2009 (McCracken and Beer, 2014). To investigate the possible Sun-climate connection we analyzed the regional tree-ring chronologies covering the period from 1445 to 2005. A total of 36 timber cores of scots pine were sampled near the northern tree-line at Loparskaya station (68.6 N, 33.3 E), including the oldest living pine with more than 560 years of age. Ring widths were measured with a precision of 0.01 mm by using a self-developed image analysis system (scanner and relevant software) (Kanatjev et al., Instruments and Experimental Technicues, 57, 214-217, 2014). The data were processed using modern methods adpoted in dendrochronology (cross-dating and standardization) with the help of COFECHA and ARSTAN programs. The analysis revealed significant cooling events, coinciding with the Spoerer (1400-1540), Maunder (1645-1715), Dalton (1790-1830), and Gleissberg (1880-1910) Grand Solar Minima. The application of MTM-spectrum analysis and continuous wavelet transform for the Loparskaya tree-ring chronology identified the existence of the main cycles of solar activity (11, 20-25, and ~ 100 years). The main solar factors acting on climate and atmosphere are solar radiation and cosmic rays, influencing the cloud cover of the atmosphere. As solar and cosmic ray proxies we used sunspot number and Be^10 cosmogenic isotope records respectively. To examine the relationship in time-frequency scale between tree-ring growth and solar activity, the cross wavelet transform and wavelet coherence were applied to the time series. The wavelet coherence analysis revealed a strong coherence in the 8-13 and 20-30 year bands indicating a possible link between solar activity and climate change on a regional scale. Our results demonstrate the possibility of using polar tree-ring widths as indicators of solar and climate changes in the past.