A hypothetical approach to determining the effect of palaeorotational rates on Earth's Neoproterozoic palaeoclimate

Revolving at a present rotation rate of approximately one revolution every 24 h, the Earth is regarded as a non-stationary sphere in space, covered with an extremely thin atmosphere in comparison with its radius. Apart from the frequency endorsed by the diurnal rotation rate, the Earth is also subject to other cycles on the seasonal and annual scales. Spatial and temporal climate variability are strongly influenced by these cycles. In this study the consequence of current and palaeorotational rates on the Earth's climate is explored. This is achieved by comparing results from atmospheric general circulation model (AGCM) simulations with present-day and palaeorotational rates. An estimated Neoproterozoic (900 Ma) palaeorotational rate related to an 18.2-h diurnal cycle has been introduced. To conserve internal energy balances in the Earth-atmosphere system, and to avoid uncertainties concerning palaeocontinental and ocean distribution, the present land-sea-atmosphere configuration has been retained. As a result of these constraints, only deviations in the average of planetary scale atmospheric circulation patterns, such as the vertical profile of the zonal average of meridional and zonal wind fields, are explored. Results are consistent with previous findings, suggesting an equatorward latitudinal shift of planetary scale circulation cells, accompanied by reduced wind speed components throughout the atmosphere, when the 900 Ma palaeorotational rate is employed in the AGCM simulation.