Reverse weathering as a long-term stabilizer of marine pH and planetary climate

Isson, Terry T.; Planavsky, Noah J.

doi:10.1038/s41586-018-0408-4

Cited by 197 publications

(171 citation statements)

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“…Authigenic clay formation in the oceans—reverse weathering—is a relatively minor part of the modern global carbon cycle, but it is likely to have been more important earlier in Earth's history (Isson & Planavsky, ). The switch to a biologically controlled Si cycle—where the majority of SiO 2 fluxes in the oceans are biogenic—caused a dramatic drop in dissolved marine Si concentrations (Siever, ).…”

Section: Discussionmentioning

confidence: 99%

“…Reverse weathering in essence recycles carbon within the ocean‐atmosphere reservoir. This process makes carbon export from the system less efficient by increasing the amount of silicate weathering required to sequester an equal amount of carbon relative to a system with less extensive reverse weathering (Isson & Planavsky, ). Thus, all else being equal, an increase in reverse weathering will elevate the amount of carbon in the ocean‐atmosphere reservoir and thus baseline p CO 2 levels (Figures and ).…”

Section: Climate Regulation Through the Carbon Cyclementioning

confidence: 99%

“…Direct bottom‐water temperature and pH controls on mineral dissolution rates ought to establish a negative feedback with atmospheric CO 2 levels as well, but the chemistry of porewaters (and waters within fractured oceanic crust) can evolve significantly with depth, and do not necessarily reflect surface water conditions. Reverse silicate weathering feedback . The flux of CO 2 to the ocean‐atmosphere system derived from reverse weathering is sensitive to marine pH conditions and thus p CO 2 (Isson & Planavsky, ; Sillén, , ). This link results in a stabilizing climate feedback.…”

Section: Climate Regulation Through the Carbon Cyclementioning

confidence: 99%

“…Elevated rates of degassing have been predicted from geophysical models for the Precambrian relative to the modern (e.g., Holland, ; O'Neill et al, ; Tajika & Matsui, ), and on this basis carbonate export tied to silicate weathering must be proportionally larger. Higher dissolved silica and iron levels that are hallmark features of the Precambrian ocean gave rise to conditions that favored enhanced rates of reverse weathering, and dampened marine weathering rates (Isson & Planavsky, ). By this framework, it follows that the ratio of terrestrial to marine silicate weathering rates would have been higher in the Precambrian.…”

Section: Evolution Of the Global Carbon Cyclementioning

confidence: 99%

“…Reverse silicate weathering feedback. The flux of CO 2 to the ocean-atmosphere system derived from reverse weathering is sensitive to marine pH conditions and thus pCO 2 (Isson & Planavsky, 2018;Sillén, 1961Sillén, , 1967. This link results in a stabilizing climate feedback.…”

Section: Mass Balance and Stabilizing Feedbacksmentioning

confidence: 99%

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Evolution of the Global Carbon Cycle and Climate Regulation on Earth

Isson

Planavsky

Coogan

et al. 2020

Global Biogeochemical Cycles

108

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The existence of stabilizing feedbacks within Earth's climate system is generally thought to be necessary for the persistence of liquid water and life. Over the course of Earth's history, Earth's atmospheric composition appears to have adjusted to the gradual increase in solar luminosity, resulting in persistently habitable surface temperatures. With limited exceptions, the Earth system has been observed to recover rapidly from pulsed climatic perturbations. Carbon dioxide (CO2) regulation via negative feedbacks within the coupled global carbon‐silica cycles are classically viewed as the main processes giving rise to climate stability on Earth. Here we review the long‐term global carbon cycle budget, and how the processes modulating Earth's climate system have evolved over time. Specifically, we focus on the relative roles that shifts in carbon sources and sinks have played in driving long‐term changes in atmospheric pCO2. We make the case that marine processes are an important component of the canonical silicate weathering feedback, and have played a much more important role in pCO2 regulation than traditionally imagined. Notably, geochemical evidence indicate that the weathering of marine sediments and off‐axis basalt alteration act as major carbon sinks. However, this sink was potentially dampened during Earth's early history when oceans had higher levels of dissolved silicon (Si), iron (Fe), and magnesium (Mg), and instead likely fostered more extensive carbon recycling within the ocean‐atmosphere system via reverse weathering—that in turn acted to elevate ocean‐atmosphere CO2 levels.

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Section: Discussionmentioning

confidence: 99%

Section: Climate Regulation Through the Carbon Cyclementioning

confidence: 99%

Section: Climate Regulation Through the Carbon Cyclementioning

confidence: 99%

Section: Evolution Of the Global Carbon Cyclementioning

confidence: 99%

Section: Mass Balance and Stabilizing Feedbacksmentioning

confidence: 99%

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Evolution of the Global Carbon Cycle and Climate Regulation on Earth

Isson

Planavsky

Coogan

et al. 2020

Global Biogeochemical Cycles

108

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Ocean alkalinity, buffering and biogeochemical processes

Middelburg

Soetaert

Hagens

2019

Preprint

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Alkalinity, the excess of proton acceptors over donors, plays a major role in ocean chemistry, in buffering and in calcium carbonate precipitation and dissolution. Understanding alkalinity dynamics is pivotal to quantify ocean carbon dioxide uptake during times of global change. Here we review ocean alkalinity and its role in ocean buffering as well as the biogeochemical processes governing alkalinity and pH in the ocean. We show that it is important to distinguish between measurable titration alkalinity and charge balance alkalinity that is used to quantify calcification and carbonate dissolution and needed to understand the impact of biogeochemical processes on components of the carbon dioxide system. A general treatment of ocean buffering and quantification via sensitivity factors is presented and used to link existing buffer and sensitivity factors. The impact of individual biogeochemical processes on ocean alkalinity and pH is discussed and quantified using these sensitivity factors. Processes governing ocean alkalinity on longer time scales such as carbonate compensation, (reversed) silicate weathering, and anaerobic mineralization are discussed and used to derive a close-to-balance ocean alkalinity budget for the modern ocean. Plain Language SummaryThe ocean plays a major role in the global carbon cycle and the storage of anthropogenic carbon dioxide. This key function of the ocean is related to the reaction of dissolved carbon dioxide with water to form bicarbonate (and minor quantities of carbonic acid and carbonate). Alkalinity, the excess of bases, governs the efficiency at which this occurs and provides buffering capacity toward acidification. Here we discuss ocean alkalinity, buffering, and biogeochemical processes and provide quantitative tools that may help to better understand the role of the ocean in carbon cycling during times of global change.This reequilibration following the principles of le Chatelier (1884) provides resistance to, but does not entirely eliminate, changes in ocean carbon chemistry. Oceanic uptake of anthropogenic carbon dioxide has caused increases in dissolved carbon dioxide and total inorganic carbon concentrations and decreases in carbonate ions and ocean pH, that is, ocean acidification (Gattuso & Hansson, 2011). Ocean acidification has consequences for further ocean carbon dioxide uptake, the precipitation and dissolution of carbonate minerals, and for the functioning and survival of marine organisms (Kroeker et al., 2013). It is therefore important that we understand and are able to quantify the buffering, that is, resistance, of the ocean in

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When Did Life Likely Emerge on Earth in an RNA‐First Process?

et al. 2019

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The widespread presence of ribonucleic acid (RNA) catalysts and cofactors in the Earth′s biosphere today suggests that RNA was the first biopolymer to support Darwinian evolution. However, most “path‐hypotheses” to generate building blocks for RNA require reduced nitrogen‐containing compounds not made in useful amounts in the CO2−N2−H2O atmospheres of the Hadean. We review models for Earth′s impact history that invoke a single ∼1023 kg impactor (Moneta) to account for measured amounts of platinum, gold, and other siderophilic (“iron‐loving”) elements on the Earth and Moon. If it were the last sterilizing impactor, by reducing the atmosphere but not the mantle Moneta, would have opened a “window of opportunity” for RNA synthesis, a period when RNA precursors rained from the atmosphere onto land holding oxidized minerals that stabilize advanced RNA precursors and RNA. Surprisingly, this combination of physics, geology, and chemistry suggests a time when RNA formation was most probable, ∼120±100 million years after Moneta′s impact, or ∼4.36±0.1 billion years ago. Uncertainties in this time are driven by uncertainties in rates of productive atmosphere loss and amounts of sub‐aerial land.

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Reverse weathering as a long-term stabilizer of marine pH and planetary climate

Cited by 197 publications

References 106 publications

Evolution of the Global Carbon Cycle and Climate Regulation on Earth

Evolution of the Global Carbon Cycle and Climate Regulation on Earth

Ocean alkalinity, buffering and biogeochemical processes

When Did Life Likely Emerge on Earth in an RNA‐First Process?

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