Controlling atmospheric carbon dioxide The atmospheric concentration of carbon dioxide (CO2) has varied substantially over the past million years in tandem with the glacial cycle. Although it is widely agreed that upwelling of Southern Ocean water is a key factor, the finer details about what caused these CO2 variations are of great importance for understanding climate. Ai et al. identified three modes of change in Southern Ocean upwelling, adding a third to two previously recognized ones. This new mode can help explain better the relative timing of the glacial and CO2 cycles. Science, this issue p. 1348 Changes in wind-driven Southern Ocean upwelling made atmospheric CO2 a delayed climate amplifier during glacial cycles. Previous studies have suggested that during the late Pleistocene ice ages, surface-deep exchange was somehow weakened in the Southern Ocean’s Antarctic Zone, which reduced the leakage of deeply sequestered carbon dioxide and thus contributed to the lower atmospheric carbon dioxide levels of the ice ages. Here, high-resolution diatom-bound nitrogen isotope measurements from the Indian sector of the Antarctic Zone reveal three modes of change in Southern Westerly Wind–driven upwelling, each affecting atmospheric carbon dioxide. Two modes, related to global climate and the bipolar seesaw, have been proposed previously. The third mode—which arises from the meridional temperature gradient as affected by Earth’s obliquity (axial tilt)—can explain the lag of atmospheric carbon dioxide behind climate during glacial inception and deglaciation. This obliquity-induced lag, in turn, makes carbon dioxide a delayed climate amplifier in the late Pleistocene glacial cycles.
The dynamical evolution of the solar system is chaotic with a Lyapunov time of only ∼5 Myr for the inner planets. Due to the chaos it is fundamentally impossible to accurately predict the solar system’s orbital evolution beyond ∼50 Myr based on present astronomical observations. We have recently developed a method to overcome the problem by using the geologic record to constrain astronomical solutions in the past. Our resulting optimal astronomical solution (called ZB18a) shows exceptional agreement with the geologic record to ∼58 Ma (Myr ago) and a characteristic resonance transition around 50 Ma. Here we show that ZB18a and integration of Earth’s and Mars’ spin vector based on ZB18a yield reduced variations in Earth’s and Mars’ orbital inclination and Earth’s obliquity (axial tilt) from ∼58 to ∼48 Ma—the latter being consistent with paleoclimate records. The changes in the obliquities have important implications for the climate histories of Earth and Mars. We provide a detailed analysis of solar system frequencies (g and s modes) and show that the shifts in the variation in Earth’s and Mars’ orbital inclination and obliquity around 48 Ma are associated with the resonance transition and caused by changes in the contributions to the superposition of s modes, plus g–s mode interactions in the inner solar system. The g–s mode interactions and the resonance transition (consistent with geologic data) are unequivocal manifestations of chaos. Dynamical chaos in the solar system hence not only affects its orbital properties but also the long-term evolution of planetary climate through eccentricity and the link between inclination and axial tilt.
periods are caused by the variations in eccentricity, axial tilt, and precession of Earth's rotation and orbit. As part of the ongoing supercontinent cycle
The biological and geological future of Earth can be extrapolated based on the estimated effects of several long-term influences. These include the chemistry at Earth's surface, the cooling rate of the planet's interior, gravitational interactions with other objects in the Solar System, and a steady increase in the Sun's luminosity. An uncertain factor is the influence of human technology such as
The…
(tilt) of the Moon's orbit either adds to (major standstill) or subtracts from (minor standstill) the inclination of Earth's rotation axis (23.439°). The effect
A lunar standstill or lunistice (reminiscent of solstice) is the relative position of the Moon furthest north or furthest south from the celestial equator (measured as an angle expressed in degrees called declination of a celestial coordinate system, analogous to latitude). The Moon comes to an apparent so-called standstill as it changes at that point direction of moving between northern and south
A more detailed explanation is best considered in terms of the paths of the Sun and Moon on the celestial sphere, as shown in the first diagram. This shows the abstract sphere surrounding the Earth at the center. The Earth is oriented so that its axis is vertical.
The Sun is, by definition, always seen on the ecliptic (the Sun's apparent path across the sky) while Earth is tilted at an angle of e = 23.5° to the plane of that path and completes one orbit around the Sun in 365.25636 days, slightly longer than one year due to precession altering the direction of Earth's inclination.
The Moon's orbit around Earth (shown dotted) is inclined at an angle of i = 5.14°…
May. This variation reflects the inclination of the Earth's axis and its revolution about the … Sun. Third, the wobble of the Earth's axis of rotation has varied through time, thereby … consists of a system of cups whose rate of rotation is recorded by a speed indicator which
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