O.M. Raspopov (1), V.A. Dergachev (2),

1. LONG-TERM SOLAR ACTIVITY VARIATIONS AS A STIMULATOR OF SHARP CLIMATE CHANGES O.M. Raspopov (1), V.A. Dergachev (2), (1) St.Petersburg Branch (Filial) of Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radiowaves Propagation of RAS, St.-Petersburg, Russia, oleg@or6074.spb.edu (2) Ioffe Physico-Technical Institute of RAS, St.Petersburg, Russia. International Conference “50 years of International Geophysical Year and Electronic Geophysical Year”, 16-19 September, 2007, Suzdal, Russia

2. It is known that deep solar activity minima are accompanied by sharp climate changes. For example, the Maunder minimum of solar activity (1645-1715) stimulated the beginning of the Little Ice Age. Goal of the presentation: to give experimental evidence that not only deep solar activity minima, but also a high solar activity level can lead to sharp global climate changes through stimulation of dynamic processes at the Earth’s surface.

3. Long-term cyclicity of solar activity ● 11-year cycle of sunspot numbers (Schwabe) ● 22-23-year cycle of solar magnetic polarity changes (Hale) ● 80-90-year cycle of amplitude modulation of 11-year cycles (Gleissberg) ● 180-230-year cycle (~210-year - deVries) ● 2300-2400-year cycle (Hallstattzeit)

4. 11-year cycle 22-23 year cycle 80-90 year cycle Record of variations of sunspot numbers W. Evidence of 11- , 22-23-, and 80-90 year solar activity variations

5. Relation between variations of sunspot numbers W and variations of galactic cosmic ray fluxes

6. Galactic cosmic rays 10Be Atmosphere 14C 10Be Recording of cosmic rays and cosmogenic isotopes generation 14СО2 Neutronmonitor  Earth surface

7. The Holocene ~7200 years minimum ~5200-5400 years minimum Homeric minimum Maunder minimum Geomagnetic dipole Variations of 14C concentration in tree-rings and the Earth’s magnetic dipole moment during the Holocene

8. ~7200 years minimum Variations of 14C concentration in tree-rings and the Earth’s magnetic dipole moment during the Holocene ~5200-5400 years minimum Homeric minimum Maunder minimum Variations of 14C concentration relating to solar activity Δ14C High solar activity 2300-2400 year variations of 14C concentration Low solar activity

9. Long-term solar activity variations and climate change during the Holocene The Holocene Variations of aerosols in Greenland ice 2300-2400 year cyclicity in atmospheric circulation Global glaciers extension Swiss alpine glaciers retreat High solar activity 2300-2400 year solar cyclicity (Δ14C variations filtered in 2000-3000 year period range) Low solar activity

10. Changes in high-latitude timber line location in Scandinavia and Canada Changes in high-latitude timber line location in Finnish Lapland Reconstructed summer temperature changes in Finnish Lapland Changes in high-latitude timber line location in northern Sweden Number of dated subfossil trees collected in northern Finnish Lapland Changes in high-latitude timber line location in northern Canada Reconstructed summer temperature changes in northern Canada Timber line change in Scandinavia and Canada shows cold time intervals similar to glacier expansion time intervals

11. What could be reason for sharp cooling events during the high solar activity time intervals? Possible reason: ice-rafting events in the North Atlantic during Ice Age and the Holocene developed during warm climate condition (high solar activity) Ice-rafting event abruptly change the North Atlantic overturning circulation and displace the position of northern edge of the Gulfstream to the South and develop of sharp climatic cooling.

12. Ice-rafting events during the Holocene [Bond et al. 2002] 4 5 7 6 6 2 3 1

13. Changes of solar activity and ice-rafting events during the Holocene High solar activity Solar activity (Δ14C) Low solar activity Grand solar activity minima Ice-rafting events (IRE) Beginning of IRE correlate well with time intervals of high solar activity and sharp climate changes

14. Sharp climate changes during the Pleistocene: Dangard-Oeschger and Henrich events

15. Solar activity (10Be), temperature changes, and ice-rafting events development over the past 40 ky in the North Atlantic region Sharp climate changes correlate well with solar activity variations and development of ice-rafting events Solar activity Temperature changes Ice-rafting events

16. Conclusion The influence of long-term solar activity variations on climatic parameters at time scales from 40,000 to 10,000 years ago (the Pleistocene) and from modern period to 10,000 years ago (the Holocene) has been analyzed. Comparative analysis of temperature oscillations and solar activity variations (variations in the concentration of cosmogenic 10Be isotopes in Greenland ice and 14C isotopes in tree rings) has revealed the solar influences on climate of two kinds. On the one hand, deep solar activity minima create conditions for sharp climate changes with the 2,400-2,300-year periodicity that manifest themselves in the most pronounced way during the Holocene. On the other hand, a high solar activity level and, hence, a high level of solar irradiance gives rise to dynamic processes at the Earth’s surface, such as ice-rafting events in the North Atlantic. Computer simulation has shown that these ice-rafting events can be caused by an increase in the surface ocean temperature, i.e., the condition created by high solar activity and solar irradiance levels. Ice-rafting events sharply change the character of the North Atlantic overturning circulation (NAOC), thus displacing the Northern edge of the Gulf Stream southwards, which leads to sharp climate changes of the global nature. Analysis of the experimental data has shown that a high solar activity level was responsible for development of ice-rafting events during both the Pleistocene and Holocene. Therefore, it can be concluded that both deep solar activity minima and a high solar activity level can create conditions for sharp climate changes.

17. Conclusion Проведен анализ воздействия долговременных вариаций солнечной активности на климатические параметры на временных шкалах от 40000 до 10000 лет назад (плейстоцен) и от современной эпохи до 10000 лет назад (голоцен). Сравнительный анализ температурных изменений и вариаций солнечной активности (вариации содержания космогенных изотопов 10Be в гренландском льду и 14C в кольцах деревьев) выявил двоякого рода солнечное воздействие на климатические изменения. С одной стороны, глубокие минимумы солнечной активности создают условия для резких климатических изменений, проявлявшихся особенно четко в голоцене с 2400-2300 -летней периодичностью. С другой стороны, высокий уровень солнечной активности и, следовательно, солнечной иррадиации создают условия для развития процессов на земной поверхности, а именно, массового сброса ледниковых масс в Северную Атлантику (ice-rafting events). Результаты моделирования свидетельствуют, что подобные сбросы ледяных масс могут быть стимулированы повышением поверхностной океанической температуры, т.е. условиями, создаваемыми высокой солнечной активностью и высоким уровнем солнечной иррадиации. Ice-rafting events резко изменяют характер North Atlantic overturning circulation (NAOC), отодвигая северную оконечность Гольфстрима к югу, что приводит к резким климатическим изменениям глобального характера. Проанализированные экспериментальные данные свидетельствуют, что высокий уровень солнечной активности стимулировал развитие ice-rafting events как в плейстоцене, так и в голоцене. Таким образом, как глубокие минимумы солнечной активности, так и высокий уровень солнечной активности могут создавать условия для развития резких климатических изменений.

18. Thank you for attention Спасибо за Ваше внимание