8.4 Weathering's Role in Long-term Climate Regulation
2 min read•july 25, 2024
The regulates Earth's climate over millions of years. It involves interactions between rocks, water, and air, acting as a natural thermostat. This process has kept our planet habitable for billions of years, even helping recover from .
is a key part of this cycle. It removes CO2 from the air when rainwater reacts with rocks. The products of this reaction eventually form carbonate sediments in the oceans, locking away carbon for long periods.
Carbon-Silicate Cycle and Climate Regulation
Carbon-silicate cycle in climate regulation
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Carbon-silicate cycle operates as long-term geochemical process involving atmosphere, hydrosphere, and lithosphere interactions
Key processes encompass silicate rock weathering, weathering product transport to oceans, carbonate sediment deposition, carbonate rock subduction and metamorphism, and volcanic CO2 degassing
Cycle spans millions of years acting as Earth's climate thermostat through stabilizing
Maintained habitable conditions over billions of years and aided recovery from extreme climate events (Snowball Earth)
Silicate weathering as carbon sink
occurs when silicate minerals react with CaSiO3+2CO2+H2O→Ca2++2HCO3−+SiO2
Atmospheric CO2 dissolves in rainwater forming carbonic acid which reacts with silicate minerals removing CO2 from atmosphere
Dissolved cations and bicarbonate ions transport to oceans where marine organisms use them for shells Ca2++2HCO3−→CaCO3+CO2+H2O
results in one mole of CO2 permanently stored as carbonate sediment
Weathering process continually removes CO2 from atmosphere balancing volcanic emissions over geological timescales
Feedback Mechanisms and Anthropogenic Impacts
Weathering, climate, and tectonics feedback
Higher temperatures increase chemical weathering rates creating negative feedback loop with atmospheric CO2 levels
Increased rainfall enhances weathering rates contributing to more efficient CO2 drawdown
and mountain building expose fresh silicate rocks to weathering increasing overall CO2 consumption
produces fine-grained sediments enhancing chemical weathering efficiency
releases CO2 into atmosphere counterbalancing CO2 consumption by weathering
influenced by tectonic activity and weathering rates affects long-term carbon cycle balance
Anthropogenic impacts on weathering rates
reduces organic acid production in soils decreasing natural weathering rates
Agriculture increases exposure of minerals to weathering potentially enhancing CO2 consumption
accelerates chemical weathering of silicate and carbonate rocks but sulfuric acid contribution doesn't lead to net CO2 consumption
propose artificial acceleration of silicate weathering as geoengineering method for CO2 removal
in urban areas acts as small-scale carbon sink while reducing exposure of natural rock surfaces
increase exposure of fresh rock surfaces potentially accelerating weathering and CO2 consumption
may increase global weathering rates through rising temperatures and alter regional weathering intensity via precipitation pattern changes
Anthropogenic impacts occur on much shorter timescales than natural processes potentially disrupting long-term carbon-silicate cycle balance