Ch. 5 Climate Change and Earth Systems

Earth-system interactions

The atmosphere, hydrosphere, lithosphere, and biosphere

Climate-regulation feedback.

A response that influences the original change and loops back to climate.

Positive feedback

A feedback that amplifies the original change.

Negative feedback

A feedback that dampens or reduces the original change.

Eutrophication

Nutrient enrichment that increases primary production especially algal growth.

Hypoxia

Low dissolved oxygen in water.

Dead zones

Areas of severe hypoxia in aquatic systems.

Eutrophication (arrow chain)

Excess nutrients -> algal growth increases -> organic matter increases -> decomposition increases -> dissolved O2 decreases.

Why warming increases dead-zone risk

Warmer water tends to hold less dissolved oxygen

Reservoir

A place where carbon is stored.

Flux

The movement of carbon from one reservoir to another.

Source

A reservoir or system that releases more carbon than it takes up.

Sink

A reservoir or system that takes up more carbon than it releases.

Residence time

How long carbon remains in a reservoir.

Slow carbon cycle timeframe

Occurs over thousands to millions of years.

Processes in the slow carbon cycle

Atmospheric CO2 -> chemical weathering -> transport by rivers to the ocean -> carbon becomes minerals and sediments -> sedimentary rock -> subduction -> metamorphism -> volcanic outgassing -> atmospheric CO2.

Weathering

A slow-carbon-cycle process and a long-term negative climate feedback.

Subduction

Carries carbon-bearing rock into Earth.

Metamorphism

A slow-carbon-cycle process that occurs after subduction and before volcanic outgassing.

Volcanic outgassing

Returns CO2 to the atmosphere.

Fast carbon cycle

Occurs over days to decades and moves carbon rapidly among the atmosphere

Processes in the fast carbon cycle

Photosynthesis removes CO2 from the atmosphere; respiration and decomposition return CO2 to the atmosphere; air-sea exchange moves CO2 between the atmosphere and surface ocean.

Fossil-fuel combustion in the carbon cycle

Rapidly transfers carbon from the slow cycle into the fast cycle.

Major carbon sinks

Vegetation, soils, and oceans

Ocean carbon cycle

The ocean stores and transports carbon through the biological pump, solubility pump, and ocean circulation.

Biological pump

Phytoplankton use CO2 in photosynthesis; carbon moves through the food web; dead organic matter and waste sink, some carbon is decomposed at depth and some carbon remains stored in the deep ocean or sediments

Solubility pump

Cold water dissolves more CO2 than warm water. Dense cold water can sink and carry dissolved carbon into deeper ocean waters

Seawater density

Density increases when water is colder and/or saltier.

Thermohaline circulation

Global ocean circulation driven by differences in temperature and salinity.

Basic thermohaline pattern

Warm shallow currents move poleward, cool and become denser, sink, travel as deep currents, and eventually rise again.

Effect of warming on CO2 solubility

Warming decreases CO2 solubility, so warmer water stores less dissolved CO2.

Stratification

The layering of water masses. Warming can increase stratification and reduce mixing between layers.

Effect of freshwater input on salinity

Freshwater input lowers salinity.

Effect of lower salinity on density

Lower salinity lowers water density.

Deep-water formation

The sinking of dense water into deeper ocean layers; changes in density can alter this process.

How climate warming can alter ocean carbon storage

Warming can decrease CO2 solubility, increase stratification, reduce mixing, lower salinity and density through freshwater input, alter deep-water formation, and change deep-ocean carbon storage.

The Blob

A North Pacific marine heat wave that began in 2013-2014, reached about 2.5 degrees C above typical conditions in some areas, and affected marine food webs and ecosystems along the Pacific coast.

Chapter 5 big idea

Climate change affects nutrient cycling, the carbon cycle, and ocean carbon storage through feedbacks, warming, and altered circulation.