Milankovitch theory

Much of the variation in these time series for the past 700 kyr can be described by a combination of a 100 kyr cycle plus additional cycles with periods of 20 and 40 kyr. This result immediately suggests that the ice-age cycles are caused by variations in the amount and seasonality of solar radiation reaching the Earth (insolation), because the 20, 40, and 100 kyr periods of climate history match the periods of cyclic variations in Earth s orbit and axial tilt, line hypothesis that these factors control climate was proposed by Milutin Milankovitch in the early part of the 20th century and is widely known as "Milankovitch Theory." It is now generally accepted that the Milankovitch variations are the root cause of the important 20 and 40 kyr climate cycles. The 100 kyr cycle, however, proves to be a puzzle. The magnitude of the insolation variation at this periodicity is relatively trivial, but the 100 kyr cycle dominates the climate history of the last 700 kyr. Further,... 

An important illustration of the high level of uncertainty of theoretical estimates about the causes of climate change is the recent re-evaluation of the role of Milankovitch mechanisms as the main factor in climatic paleodynamics. The Milankovitch mechanism links climatic change with changes in the orientation of the Earth in its orbit around the Sun. According to Milankovitch theory (Crowley... 

Winograd, I.J., Szabo, B.J., Coplen, T.B. and Riggs, A.C., 1988, A 250,000-year climatic record from Great Basin vein calcite Implications for Milankovitch theory. Science 242 1275-1280. 

At a coarse level of time resolution, episodes of speleothem growth record relatively wet periods in semi-arid climates, or relatively warm periods in cool temperate climates. The precise dating of speleothems allows them to be used to test Milankovitch theory and to calibrate the timing of palaeo-climate fluctuations. Counting of physical or chemical laminae allows the duration of climatically significant intervals to be determined. 

Farley and Patterson (1995) and Patterson and Farley (1998) interpreted the variability of the He accumulation in deep-sea sediments to directly reflect the cyclicity of the accretion rate of IDPs, i.e. changes in delivery of IDPs from space. This interpretation supports a recent hypothesis by Muller and MacDonald (1995, 1997a,b,c) that the accretion rate of cosmic dust to the earth varies with the 100 ka cycle of Earth s inclination and may be responsible—in contrast to the widely accepted Milankovitch theory—for forcing the 100 ka climate cycle. 

Imbrie J, Hays JD, Martinson DG, McIntyre A, Mix AC, Morley JJ, Pisias NG, Prell W L, Shackleton NJ (1984) The orbital theory of Pleistocene climate Support from a revised chronology of the marine record. In Milankovitch and Climate, Vol. 1. Berger A, Imbrie J, Hays J, Kukla G, Saltzman B (eds) D. Reidel, Boston p 269-305... 

To test Milankovitch s theory, it was not enough to know the dates of a few past ice ages. The theory predicted that the climate system has an unsteady pulse, with ice ages of varying severity, in which the three major rhythms should be discernible. To take this pulse. 

Milankovitch, M. Mathematische Klimalehre und astronomische Theorie der Klimaschwankungen. In Kdppen-Geiger Handbuch der Klimatologie 1, Teil A, Berlin (1930). Verlag Gebr. Borntraeger. 

Milankovitch, M. (1920). Theorie mathematique des phenomenes ther-miques produits par la radiation solaire. Academic Yugoslave des Sciences et des Art de Zagreb, Gauthier-Villars. 

The prevalent theory is that these major fluctuations in global climate, associated with the glacial cycles, were caused by variations in insolation at critical latitudes and seasons. In particular, ice sheet growth and retreat is thought to be sensitive to high northern-latitude summer insolation as proposed by Milankovitch in his original astronomical theory. 

The second type of models includes a representation of the seasonal cycle, and has been used to investigate the orbital theory of Milankovitch. In this case, the seasonal variations in orbital insolation are resolved. However, as for the first type of models, past changes in ice cover are assumed to follow the simulated variations in the extent of perennial snow. This approach assumes that ice cover and the powerful ice albedo feedback are governed only by temperature, as the extent of snow in these models is fixed to the latitude with a temperature of 0°C. In reality, the growth and decay of land-based ice sheets are governed by the balance of accumulation and ablation. Therefore, when investigating changes in ice cover, it is necessary to include an appropriate representation of the dynamics and mass balance of ice sheets in the model. 

Milankovic, Milutin (1879-1958) Serbian civil engineer and geophysicist, best known for his theory of ice ages, relating variations of the earth s orbit and long-term climate change, now known as Milankovitch cycles. 

Merrihue CM, Turner G (1966) J Geophys Res 71 2852 Milankovitch M (1920) Theorie Mathematique des Phenomenes Thermique produits par la radiation solaire. Gauthier-Villaris, Paris Nyquist LE (1977) Phys Chem Earth 10 103 Odom AL, Rink WJ (1988) Geology 17 55 Pal DK, Tuniz C, Moniot RK, Kruse TH, Herzog GF (1982) Science 218 787... 

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