Lecture 2: Earth as a Self-Regulating System

Gaia hypothesis

Earth as a self-regulating system through feedback.

Geosphere

Solid Earth, including rocks and minerals.

Hydrosphere

Water components, including oceans and ice.

Biosphere

All living organisms on Earth.

Atmosphere

Layer of gases surrounding Earth.

Steady state

Condition where system variables remain constant.

Fluxes

Movement of energy and matter between reservoirs.

Residence times

Average time matter spends in a reservoir.

Positive feedback

Amplifies initial changes in a system.

Negative feedback

Dampens or reduces changes in a system.

Reservoirs

Storage locations for matter and energy.

Plate tectonics

Movement of Earth's plates relative to each other.

Divergent boundaries

Where tectonic plates move apart.

Convergent boundaries

Where tectonic plates move towards each other.

Subduction zones

Areas where oceanic crust is destroyed.

Volcanic eruptions

Release of gases like CO2 into atmosphere.

Chemical weathering

Process removing CO2 from the atmosphere.

Cryosphere

Frozen water components of the Earth.

Stromatolites

Fossilized evidence of early life, 3.5 Ga.

Feedback mechanisms

Processes that regulate Earth's systems.

Earth's interior

Includes magmas and gases beneath the surface.

Abiotic oxygen generation

Oxygen produced by non-living processes.

Weak Young Sun

Early Earth CO2 source compensating for solar output.

Divergent Plate Boundaries

Locations where tectonic plates pull apart.

Mid-Atlantic Ridge

Example of divergent plate boundary formation.

Carbon Degassing

Release of CO2 from Earth's reservoirs.

Submarine Volcanoes

Underwater volcanoes contributing to CO2 emissions.

Anthropogenic Emissions

Human-induced CO2 from fossil fuels and cement.

GtCO2

Gigatonne of CO2, equals one billion tonnes.

Natural Emissions

CO2 released from natural processes like volcanism.

Mount Pinatubo

Volcano in the Philippines, significant eruption in 1991.

Flux

Mass transfer rate, measured in kg/year.

Reservoir

Storage of mass, measured in M units.

Steady State

Condition where input equals output flux.

Perturbation

Change in system affecting concentration over time.

Input Flux (Jin)

Mass entering the reservoir per unit time.

Output Flux (Jout)

Mass leaving the reservoir per unit time.

Unbalanced Fluxes

Condition where Jin exceeds Jout, not steady state.

Hydrosphere Interaction

Seawater alters rock composition at mid-ocean ridges.

Black Smokers

Hydrothermal vents releasing hot metal-rich fluids.

White Smokers

Hydrothermal vents with different mineral compositions.

Geosphere

Earth's solid outer layer interacting with hydrosphere.

Carbon Reservoirs

Natural storage locations for carbon in Earth.

Residence Time

Average time a particle stays in a system.

Steady State

Input equals output in a system.

Global CO2 Emissions

CO2 released from fossil fuels and cement.

Atmospheric CO2 Reservoir

Atmosphere holds 750 Mt of CO2.

Photosynthesis

Process plants use to absorb CO2.

Food Chain

Pathway through which energy and nutrients flow.

Chemical Weathering

Natural process releasing CO2 into the atmosphere.

Carbonic Acid

CO2 dissolved in water forms this acid.

Marine Organisms

Organisms that incorporate salts like CaCO3.

Ocean CO2 Absorption

One-third of human-emitted CO2 absorbed by oceans.

Ocean Acidification

Decreasing pH due to rising CO2 levels.

Positive Feedback

Reinforces initial changes in a system.

Negative Feedback

Counters or dampens initial changes in a system.

Albedo Effect

Reflectivity of Earth's surface affecting temperature.

Global Thermostat

Chemical weathering regulates atmospheric CO2 levels.

Fluxes

Flows between or within Earth's reservoirs.

Interconnected Reservoirs

Solid Earth, hydrosphere, biosphere, atmosphere are linked.

Anthropogenic CO2 Increase

Human activities significantly raise atmospheric CO2.

Research on Feedback Mechanisms

Active study of climate system interactions.

Mauna Loa Observatory

Location for monitoring atmospheric CO2 levels.

Carbon Cycle Processes

Includes photosynthesis, respiration, decay, and weathering.

Terrestrial Ecosystems

Land-based systems that absorb CO2.

Oceanic CO2 Sink

Oceans absorb CO2, slowing atmospheric increase.