Probable conexión entre el comportamiento del campo magnético terrestre y cambios climáticos durante el cenozoico tardío

ORGEIRA, MARÍA J.; DUHAU, S.; GOGORZA, C. S.; SINITO, A.M.

Montevideo

Congreso; Latinmag 2013; 2013

LATINMAG

Although solar activity and orbital cycles are the most important climate forcing, other variables are becoming significant in recent times. The sun activity is clearly a significant driver of changes, not only in climate but in the behaviour of the ionosphere and the magnetosphere, and external magnetic field (Courtillot et al, 2007). This field modulates the incoming cosmogenic ray flux which is recognized as a potential driver of climate. Geomagnetic field variations found at irregular intervals over the past few millennia seem to be Latinmag Letters, Volume 3, Special Issue (2013), OD01, 1-4. Proceedings Montevideo, Uruguay OD01 - 2/4 correlated with significant climate events in eastern North Atlantic region (Courtillot et al, 2007). Due to this, a mechanism according to which the internal magnetic field itself could somewhat trigger significant climate changes is suggested; possibly through the cosmic ray/low cloud connection, during periods of extreme tilt of the geomagnetic dipole, climate changes could take place. Then, the geomagnetic field can modulate the incoming of cosmogenic ray flux. Meanwhile, there is a correlation between cosmogenic ray and cloud cover; higher cosmogenic ray flux lead to more low clouds and thus higher albedo and, as a consequence, lower earth surface temperatures. But the process is no simply and the mentioned relation seems to follow a geographycal pattern, with areas of highly significant correlation and almost no correlation in other areas. Briefly, there are two main hypotheses proposed about the influence of the geomagnetic field; the more simply one which indicates that the lower field intensity would promote more radiation income (including cosmic), more cloud formation, which could induce cold weather. And the other associating the subject to the presence of jerks, and it is related to simultaneous sudden changes in intensity and direction of the geomagnetic field. This takes into account the inclination of the dipole, it means the equatorial component. If this component is important, cosmic radiation would reach lower latitudes, where there is more moisture and that produce more clouds and cooler climate, which can happen with increases or decreases in intensity of the geomagnetic field. A combination of both processes is also posible. On the other hand, when the axial dipole intensity is high, the influence on climate is directly linked to solar activity; during periods of minimum solar activity the weather cools and conversely, with maximum activity heats up. The present contribution shows some examples with positive and negative correlation between geomagnetic field and paleoclimate behavior, taking into account the hypothesis proposed at present