Lithologic Controls on Silicate Weathering Regimes of Temperate Planets. (arXiv:2008.11620v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hakim_K/0/1/0/all/0/1">Kaustubh Hakim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bower_D/0/1/0/all/0/1">Dan J. Bower</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tian_M/0/1/0/all/0/1">Meng Tian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Deitrick_R/0/1/0/all/0/1">Russell Deitrick</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Auclair_Desrotour_P/0/1/0/all/0/1">Pierre Auclair-Desrotour</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kitzmann_D/0/1/0/all/0/1">Daniel Kitzmann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dorn_C/0/1/0/all/0/1">Caroline Dorn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mezger_K/0/1/0/all/0/1">Klaus Mezger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Heng_K/0/1/0/all/0/1">Kevin Heng</a>
The atmospheres of temperate planets may be regulated by geochemical cycles.
Silicate weathering provides essential negative feedback to the
carbonate-silicate cycle (carbon cycle) to maintain temperate climates on Earth
and possibly on Earth-sized temperate exoplanets. The intensity of weathering
is normally attributed to the kinetics of weathering reactions of individual
minerals. The implementation of a transport-controlled weathering model shows
that when the CO$_2$ volume mixing ratio decreases or surface temperature
increases, equilibrium thermodynamics rather than kinetics exerts a strong
control on weathering. Modeling the weathering of all minerals in a given rock
instead of individual minerals is crucial. The transition between kinetically-
and thermodynamically-limited regimes of weathering is strongly sensitive to
rock lithology. Application of this model to Earth suggests that global mean
continental granite and seafloor basalt weathering rates are likely limited by
the supply of fresh rocks, yet regional weathering rates can be influenced by
both kinetics and thermodynamics. Consideration of total dissolved inorganic
carbon as a proxy for weathering results in another CO$_2$ drawdown regime:
CO$_2$ dissolution, where aqueous bicarbonate and carbonate ions produced by
rock weathering are lower in concentration than aqueous CO$_2$. Upper limits to
weathering as a function of lithology are provided to calculate the maximum
impact of weathering on the carbon cycle. The temperature-sensitivity of the
thermodynamically-limited silicate weathering provides a potential positive
feedback to the carbon cycle which may shift the inner edge of the habitable
zone.
The atmospheres of temperate planets may be regulated by geochemical cycles.
Silicate weathering provides essential negative feedback to the
carbonate-silicate cycle (carbon cycle) to maintain temperate climates on Earth
and possibly on Earth-sized temperate exoplanets. The intensity of weathering
is normally attributed to the kinetics of weathering reactions of individual
minerals. The implementation of a transport-controlled weathering model shows
that when the CO$_2$ volume mixing ratio decreases or surface temperature
increases, equilibrium thermodynamics rather than kinetics exerts a strong
control on weathering. Modeling the weathering of all minerals in a given rock
instead of individual minerals is crucial. The transition between kinetically-
and thermodynamically-limited regimes of weathering is strongly sensitive to
rock lithology. Application of this model to Earth suggests that global mean
continental granite and seafloor basalt weathering rates are likely limited by
the supply of fresh rocks, yet regional weathering rates can be influenced by
both kinetics and thermodynamics. Consideration of total dissolved inorganic
carbon as a proxy for weathering results in another CO$_2$ drawdown regime:
CO$_2$ dissolution, where aqueous bicarbonate and carbonate ions produced by
rock weathering are lower in concentration than aqueous CO$_2$. Upper limits to
weathering as a function of lithology are provided to calculate the maximum
impact of weathering on the carbon cycle. The temperature-sensitivity of the
thermodynamically-limited silicate weathering provides a potential positive
feedback to the carbon cycle which may shift the inner edge of the habitable
zone.
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