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Saul
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There are a series of papers that support the assertion that geomagnetic excursions cause Younger Dryas magnitude abrupt climate change events.
There is a geomagnetic excursion that correlates with the Younger Dryas abrupt climate change and with similar abrupt climate change events.
Looking at how the geomagnetic field has changed in the past (the frequency of reversals, the change in the periodicity of excursions during the current ice epoch, and the periodicity of the Younger Dryas type abrupt climate events, the following hypothesis can be formed.
The periodicity of the forcing event that causes the geomagnetic excursion is around 12 kyr. The same forcing event (smaller magnitude) causes geomagnetic jerks which are secular geomagnetic field changes (regions on the planet surface that have stronger normal or reversed polarity in reference to the current geomagnetic field configuration.
It appears the cyclic event that is forcing the geomagnetic field is external. The field changes are too closely spaced to be due to internal changes in the planet. As the liquid core is conductive rapid field changes in the liquid core induce counter fields in the conductive liquid which inhibits rapid field changes.
The Paleoclimatic data shows that the Younger Dryas cooling event occurred over 15 years in three 5 years steps. The entire Younger Dryas cooling event was complete in 40 years. The planet cooled from interglacial warm to within 25% of the glacial temperatures. Temperature in the North America cooled by around 18F. What is interesting is the Younger Dryas is one of a series of similar cooling events, including the termination of past interglacial periods.
During the glacial period the external forcing event has less affect on the geomagnetic field and planetary temperature as the planet is already cold and vast regions of the planet's surface is covered with ice sheets which insulate the planet's surface from the cyclic forcing event, and planetary temperature is already very cold so increased GCR has less effect.
The affect of the external cyclic event that is forcing the geomagnetic event it appears is dependent on the earth’s axis tilt at the time of the event, timing of perihelion, the eccentricity of the earth’s orbit, the distribution of the continents on the surface of the planet, and the area of the planet’s surface covered by ice sheets.
http://www.paleomag.net/members/qingsongliu/References/EPSL/Thouveny%20excursions%20since%20400%20ka%20EPSL%202004.pdf
There is a geomagnetic excursion that correlates with the Younger Dryas abrupt climate change and with similar abrupt climate change events.
Looking at how the geomagnetic field has changed in the past (the frequency of reversals, the change in the periodicity of excursions during the current ice epoch, and the periodicity of the Younger Dryas type abrupt climate events, the following hypothesis can be formed.
The periodicity of the forcing event that causes the geomagnetic excursion is around 12 kyr. The same forcing event (smaller magnitude) causes geomagnetic jerks which are secular geomagnetic field changes (regions on the planet surface that have stronger normal or reversed polarity in reference to the current geomagnetic field configuration.
It appears the cyclic event that is forcing the geomagnetic field is external. The field changes are too closely spaced to be due to internal changes in the planet. As the liquid core is conductive rapid field changes in the liquid core induce counter fields in the conductive liquid which inhibits rapid field changes.
The Paleoclimatic data shows that the Younger Dryas cooling event occurred over 15 years in three 5 years steps. The entire Younger Dryas cooling event was complete in 40 years. The planet cooled from interglacial warm to within 25% of the glacial temperatures. Temperature in the North America cooled by around 18F. What is interesting is the Younger Dryas is one of a series of similar cooling events, including the termination of past interglacial periods.
During the glacial period the external forcing event has less affect on the geomagnetic field and planetary temperature as the planet is already cold and vast regions of the planet's surface is covered with ice sheets which insulate the planet's surface from the cyclic forcing event, and planetary temperature is already very cold so increased GCR has less effect.
The affect of the external cyclic event that is forcing the geomagnetic event it appears is dependent on the earth’s axis tilt at the time of the event, timing of perihelion, the eccentricity of the earth’s orbit, the distribution of the continents on the surface of the planet, and the area of the planet’s surface covered by ice sheets.
http://www.paleomag.net/members/qingsongliu/References/EPSL/Thouveny%20excursions%20since%20400%20ka%20EPSL%202004.pdf
Geomagnetic moment variation and paleomagnetic excursions since 400 kyr BP: a stacked record from sedimentary sequences of the Portuguese margin
A paleomagnetic study was performed in clayey-carbonate sedimentary sequences deposited during the last 400 kyr on the Portuguese margin (Northeast Atlantic Ocean). Declination and inclination of the stable remanent magnetization present recurrent deviations from the mean geomagnetic field direction. The normalized intensity documents a series of relative paleointensity (RPI) lows recognized in other reference records. Three directional anomalies occurring during RPI lows chronologically correspond to the Laschamp excursion (42 kyr BP),the Blake event (115-122 kyr BP) and the Icelandic basin excursion (190 kyr BP). A fourth directional anomaly recorded at 290 kyr BP during another RPI low defines the ‘Portuguese margin excursion’. Four non-excursional RPI lows are recorded at the ages of the Jamaica/Pringle Falls,Mamaku,Calabrian Ridge 1,and Levantine excursions. The RPI record is characterized by a periodicity of approx. 100 kyr,paleointensity lows often coinciding with the end of interglacial stages. This record sets the basis of the construction of an authigenic 10Be/9Be record from the same sedimentary sequences [Carcaillet et al.,this issue].
Spectral analyses of the RPI record reveal a dominant periodicity at 100 kyr,already reported
by other studies (e.g. [41,59,60]). The RPI and N18O records also present a phase shift of 18 kyr: RPI lows often coincide with the end of interglacial or interstadial stages. The geomagnetic moment loss (-30%) over the last two millennia deduced from archeomagnetic results (e.g. [38,39]) might foreshadow the next excursion for the end of our present interglacial, even though this loss started 2200 years ago from an exceptionally high geomagnetic moment value.
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