(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.

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

LONG-TERM SOLAR ACTIVITY VARIATIONS AS A STIMULATOR OF

SHARP CLIMATE CHANGES

International Conference “50 years of International Geophysical Year andElectronic Geophysical Year”, 16-19 September, 2007, Suzdal, Russia

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.

Long-term cyclicity of solar Long-term cyclicity of solar activityactivity

● ● 11-11-year cycle of sunspot numbersyear cycle of sunspot numbers ((Schwabe)Schwabe)

● ● 22-23-year cycle of solar magnetic 22-23-year cycle of solar magnetic polarity changespolarity changes ( (Hale)Hale)

● ● 80-90-year cycle of amplitude 80-90-year cycle of amplitude modulation of 11-year cycles modulation of 11-year cycles ((Gleissberg)Gleissberg)

●● 180180--230-230-year cycleyear cycle ( (~~210-210-year - year - deVries)deVries)

● ● 2300-2400-year cycle2300-2400-year cycle ( (Hallstattzeit)Hallstattzeit)

Record of variations of sunspot numbers W.

Evidence of 11- , 22-23-, and 80-90 year solar activity

variations

80-90 year cycle

22-23 year cycle

11-year cycle

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

1010BeBe

Recording of cosmic rays and Recording of cosmic rays and cosmogenic isotopes generationcosmogenic isotopes generation

Atmosphere10Be

Galactic cosmic rays

14C

Earth surface

14СО2

Neutron monitor

Variations of 14C concentration in tree-ringsand the Earth’s magnetic dipole moment

during the Holocene

Geomagneticdipole

Maunderminimum

Homericminimum

~5200-5400 years minimum

~7200 years minimum

The Holocene

Maunderminimum

Homericminimum

~5200-5400 years minimum

~7200 years minimum

Low solar activity

High solar activity

Δ14C

Variations of 14C concentration in tree-ringsand the Earth’s magnetic dipole moment during the Holocene

Variations of 14C concentration relating tosolar activity

2300-2400 yearvariations of 14C concentration

High solar activity

The Holocene

Low solar activity

Variations of aerosols inGreenland ice2300-2400 year cyclicityin atmospheric circulation

Global glaciers extension

Swiss alpine glaciersretreat

2300-2400 year solarcyclicity (Δ14C variationsfiltered in 2000-3000 yearperiod range)

Long-term solar activity variations and climate change during the Holocene

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 subfossiltrees collected in northernFinnish Lapland

Changes in high-latitude timber line location in northern Canada

Reconstructed summer temperature changes in northern CanadaTimber line change in Scandinavia and Canada shows cold time

intervals similar to glacier expansion time intervals

What could be reason for sharp cooling events during the high solar activity time intervals?

Possible reason: ice-rafting events in the North Atlanticduring Ice Age and the Holocene developed during warmclimate condition (high solar activity)

Ice-rafting event abruptly change the North Atlantic overturning circulationand displace the position of northern edge of the Gulfstream to the South and develop of sharp climatic cooling.

Ice-rafting events during the Holocene [Bond et al. 2002]

12 3

4 566

7

Changes of solar activity and ice-rafting events during the Holocene

High solar activity

Solar activity (Δ14C)

Low solar activity

Ice-raftingevents(IRE)

Grand solaractivityminima

Beginning of IRE correlate well with time intervals of high solar activity and sharp climate changes

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

Solar activity (10Be), temperature changes, and ice-rafting eventsdevelopment over the past 40 ky in the North Atlantic region

Solar activity

Temperature changes

Ice-raftingevents

Sharp climatechanges correlate wellwith solaractivity variations anddevelopment of ice-raftingevents

ConclusionThe influence of long-term solar activity variations on climatic parameters at time scales from 40,000 to 10,000 years ago (the Pleistocene) and frommodern 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 oftwo 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.

ConclusionПроведен 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, аименно, 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.