The Thermal Effects of Magma On Ocean Heating Through Ice Ages Cycles, With Particular Reference to Interglacial Events
25 Pages Posted: 25 Oct 2018 Last revised: 8 Mar 2019
Date Written: October 2, 2018
The direct heating of oceans by volcanism is estimated using current knowledge, and extended to consider its variation through ice age cycles. The crude estimate of the current effect is c.0.7W/m2, from c.100,000 volcanoes releasing magma volumes that would raise sea levels c. 8mm pa without compensating effects. A doubling of this level can deliver the minimum incremental heat required to produce an interglacial event over 7Ka, assuming no losses. Such an effect is strongly supported by the empirical evidence available. The primary cause of this sustained interglacial increase in emissions is suggested to be increasing solid gravitational tides caused by the maximum variation of the 100Ka Milankovitch orbital eccentricity cycles, assisted by the unloading effects of >100m ocean level reduction at this time. The interglacial surges are ultimately limited by the powerful feedback from warming oceans, through evaporative cooling and increasing cloud albedo, reducing insolation to create a new higher thermal equilibrium, maintained until reducing gravitational stress, hence volcanic activity, return emissions to ice age lows. Significant volcanic peaks occuring at obliquity and precessional Milankovitch maximums may also be due to oscillations induced by the effects of these motions on Earth's visco-elastic mantle. Other lesser causes of crustal deformation have been identified that can create shorter and weaker volcanic variability, and hence climate variability, driving the variable atmospheric equilibrium temperatures that characterise the ice age cycle. To determine the above with greater precision will require improved sub aerial volcano data and correlation of their activity with climate change.
Keywords: Magma, Interglacial, Climate, Gravitational Tides, Milankovitch
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