EAS Exam 3

Carbon Cycle can be partitioned into organic and inorganic carbon

Inorganic Carbon

C-containing compounds that lack C-H or C-C bonds (typically contain C-O bonds instead)
Typically gases, inorganic acids, and rock material
Examples
• CO2 – carbon dioxide
• CaCO3 – calcium carbonate
• H 2 CO3 – carbonic acid

Organic Carbon (CH2 0)

C-containing compounds with one or more C-H or C-C bonds
Biological Molecules like alcohols, lipids/fats, carbohydrates, or proteins
Examples
• C 2 H 6 O – Ethanol
• CH 3 (CH 2 ) nCOOH – generic Lipid
• RCH(NH 2 )COOH – generic protein
• C 6 H 12 O6 - glucose

Reservoir - a pool of material at a particular time, expressed in terms of mass

Flux - Rate of inflow or outflow (mass yr-1 )

Steady state - condition in which the state of a system component is constant with time (inflow rate = outflow rate) for which residence time can be determined

Where is all of the carbon on Earth?

99.9% of carbon on Earth is sequestered in rock (limestone, carbon-rich shales, coal and oil deposits)

Other 0.1% of carbon is stored in oceans, atmosphere, living biomass

Keeling Curve

Can observe seasonal changes (red curve below) in CO 2 through the Keeling Curve!

Photosynthesis → 6𝐶𝑂! + 6𝐻! 𝑂 → 𝐶" 𝐻#! 𝑂" + 6𝑂!

Spring/Summer → (CO2 is drawn down/decreases)

Respiration → 𝐶" 𝐻#! 𝑂" + 6𝑂! → 6𝐶𝑂! + 6𝐻! 𝑂

Fall/Winter → (CO2 is accumulating/builds up in atmosphere)

CO2 info

CO2 more easily dissolves into surface water in cooler regions

Good exam question topic: CO 2 can be transported to different parts of the ocean from downwelling and upwelling

Downwelling: Cold/Salty (Denser) waters sink in polar regions. Carries dissolved CO2 into deep ocean (Thermohaline Circulation)
Upwelling: bring deep, cold ocean water to surface, waters warm, and some of
dissolved CO2 released back to atmosphere

CO2 Ocean carbon cycle pumps (short answer question - one for each)

Biological Carbon Pump - organic

❗Phytoplankton use sunlight for energy and dissolved inorganic nutrients to transform dissolved CO 2 into organic carbon; Organic carbon passes through consumers (zooplankton/bacteria) via food web...feeding, producing waste, dying, decomposing moves carbon into deep ocean (Organic Carbon Cycle)

Physical Carbon Pump - inorganic

CO 2 can be transported to different parts of the ocean from downwelling and upwelling

❗As CO2 dissolves in the ocean, it becomes available to phytoplankton that fix it into organic carbon via photosynthesis

Carbonate Pump - inorganic

❗CO 2 can be fixed into Calcium Carbonate (CaCO 3) shelled creatures skeletal structure; Sink to deep ocean floor and form limestone sediments, trapping carbon for millions of years. (Inorganic Carbon Cycle)

As CO2 dissolves in the ocean, it also can be used to form calcium carbonate shells (CaCO3) instead of being fixed biologically via photosynthesis

Inorganic Carbon Cycle

Inorganic carbon cycle - primarily functions over long-time scales (i.e. long-term is greater than 1 million years!)

CO2 Reservoir Movement

CO2 Removed from atmosphere during silicate weathering/ burial of weathered minerals
CO2 Returned to atmosphere through volcanism (volcanism driven by subduction of tectonic plates at Earth’s surface)

Weathering and Metamorphism (Understand and be able name reactants and products of…)

CaSiO_3 + CO_2 → ← CaCO_3 + SiO_2

CaSiO_3 - Wollastonite
CO_2 - Carbon dioxide
CaCO_3 - Calcium carbonate
SiO_2 - Silica

Cycles through:

Volcanic eruptions (CO_2(g))
Precipitation and direct dissolution (CO_2(g) → H_2CO_3(l))
Chemical weathering (H_2CO_3(l) → HCO_3(l))
Precipitation of CaCO_3 (HCO_3(l) → CaCO_3(s))
Subduction (CaCO_3(s))
Melt and rise of magma (CaCO_3(s) → CO_2(g))

H_2CO_3 - Carbonic acid
HCO_3 - Carbonate ion
CaCO_3 - Calcium carbonate

Know what ions are released during weathering

Calcium and Bicarbonate ions released during either weathering reaction are used by organisms to form calcium carbonate shells/skeletons in oceans. (Carbonate Pump)
Acidic rainfall
Negative feedback loop

Paleoclimatology

Paleoclimate Archive - Geologic and biologic materials that preserve evidence of past changes in climate

Paleoclimate Archive Examples
• Trees
• Corals
• Stalagmites
• Sediment Cores
• Ice Cores

Paleoclimate Proxies - Physical, chemical, and biological materials preserved within paleoclimate archives that can be analyzed

Biological Paleoclimate Proxies
includes the remains of living
organisms...
• Pollen
• Foraminifera
• Plant macrofossils (leaves, flowers, plant fragments visible to the eye)

Chemical Paleoclimate Proxy: Stable oxygen isotopes

Isotopes are atoms of the same element that have different numbers of neutrons
Isotopes of the same element have the same number of protons
Differences in the number of neutrons means isotopes have different masses
Oxygen-18 is a rare form - Found in 1 in every 500 atoms of oxygen
The ratio (relative amount) of the light (16O) and heavy (18O) oxygen in water molecules change with the climate (Specifically during the hydrological cycle!)
Isotopic Records built by comparing how many Oxygen 18’s (18O) versus Oxygen 16’s (16O) are found in fossils, ocean/lake waters, rain/snow, and ice at different time scales

What Climate Processes influence the ratio of heavy and light oxygen isotopes (Hydrological Cycle)

Evaporation - Water molecules containing LIGHT oxygen ( 16O) evaporate from the surface of the ocean more easily than heavy oxygen ( 18O) water molecules
- 16O evaporates more easily than 18O
Condensation - Heavy oxygen ( 18O) containing water molecules can condense into rainfall more easily than light oxygen ( 16O)
- 18O is preferentially removed by precipitation

Oxygen Isotopic Records: Glacials

18 O/16 O ratio ---> can tell us about past temperature or rainfall variability

16 O likes to be in gas phase (evaporate easily)

18 O likes to be in liquid phase (rains out)

INTERGLACIAL - Ocean water would contain more 16O because as ice sheets melt, the water with 16O is returned to the ocean

GLACIAL - 16O’s ‘locked’ on land in Glaciers/Ice sheets Ocean is ’heavier’ → a more 18O’s in ocean than interglacial periods. Harder to evaporate 18O’s

Ratio of 18O/16O in Foraminifera fossils is dependent on seawater temperature and extent of glaciers

“Heavier” values (more positive) during glacial times in foraminifera shells (i.e. there are more Oxygen-18’s in the ocean than normal!)

Climate in Ice ages impact amount/type of oxygen isotopes found in oceans (foraminifera) and ice

Oxygen Isotopic Records: Nuclear Forces

Strong nuclear force (keeps atom’s nucleus together)

Weak nuclear force (facilitates nuclear decay...)

Nuclear Decay/Radioactive Decay

Unstable atomic nucleus loses energy/emits energy in the form of radiation

Result: Transmutation...An atom changes from one element toanother!

Radioactive Decay - Elements undergo radioactive decay to form stable nuclei... These are called Radioactive Elements

When atoms undergo radioactive decay...it changes from one element to another...and this happens on a very measurable time scale!

Because we know in a laboratory setting how long it takes for the original element (Uranium) to decay to the new element (Thorium)...we can ‘date’ paleoclimate archives and find out hold they are!
This is called “radiometric dating”

Climate/Radiative Forcings

The change in energy flux (W/m2 ) in the atmosphere caused by natural or anthropogenic factors

Radiative forcing is a measure of the influence a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system. Earth’s surface temperature depends on this balance...

Shifting the balance causes Earth’s average temperatures to become warmer or cooler...

Positive Forcing = Warming effect

Negative Forcing = Cooling effec

The change in energy flux (W/m2) in the atmosphere caused by natural or anthropogenic factors

Factors = potential climate change mechanism

Factors to know for the exam:

Milankovitch Cycles

3 orbital forcings are used to explain leaving and entering Earth’s Ice Ages over the last~1,000,000 years
These 3 Orbital Forcings impact the amount and distribution of incoming solar radiation reaching Earth’s surface
Will not ask names or times of orbital cycles, but you need to know this slide, and that they come together to change the concentration of radiation at different latitudea nd explains how we have gone in/out of ice ages

Sun Spots

Sunspots are areas that appear dark on the surface of the Sun. They appear dark because they are cooler than other parts of the Sun’s surface
They appear dark because they are cooler than other parts of the Sun’s surface
During a grand minimum, solar magnetism diminishes, sunspots appear infrequently and less ultraviolet radiation reaches Earth. Grand minimums can last several decades to centuries

Plate Tectonics

Silicate weathering rate - atmospheric CO2 is negative coupling
Cenozoic uplift of Himalayan Mountains accelerated silicate weathering and may have triggered global cooling

Ocean Circulation Change

Major Volcanic Eruptions

Ejection of Ash Material from volcanic eruptions impacts Earth’s Climate
- Main Reaction: Sulfur Dioxide to Sulfuric Acid (creates Sulfate Aerosols)
Sulfate aerosols increase albedo of clouds, reducing solar radiation reaching Earth’s Surface → Effect: Short Term Cooling

Forest Fires

Dense wildfire smoke can temporarily block sunlight near the ground, causing regional temperatures to drop by several degrees
Wildfire smoke can also have global cooling effects by making clouds in the lower atmosphere (troposphere) more reflective or blocking sunlight in the upper atmosphere, similar to what a volcanic eruption does

Changes in atmospheric greenhouse gas

Geological time scale

We are currently in the Cenozoic Era, the Quaternary Period, and the Holocene Epoch

Younger Dryas (12,900 - 11,700 years ago)

Sudden return to glacial conditions which temporarily reversed the gradual climatic warming after the Last Glacial Maximum (LGM: 27 – 20k years ago)

Named after alpine-tundra wildflower (leaves abundant in paleoclimate sediment records in N.H.)

Sudden: Took only decades

Consequences:

Decline in Greenland temperature by ~4 – 10°C
Advancement of glaciers in N.H.
Drier conditions over N.H.

“8,200 Year Event” – Lake Agassiz

Lake Agassiz released into the North Atlantic by the Gulf Stream.

Releasing huge amounts of freshwater into North Atlantic Ocean disrupts deep ocean circulation/formation of deep water masses

Holocene Climate Optimum

Increased strength of north tropical monsoons

Orbital configurations – 8% stronger summer insolation (tropics & subtropics)

Larger temperature gradient contrast between the ocean and surrounding land

Drives stronger winds + increased precipitation from increased evaporation (warmer than average temperatures)

Medieval Warm Period (MWP)

Warm climatic conditions in North Atlantic Region (Years: 950 – 1250) (European Middle Ages)

Paleoclimate proxy records show peak warmth occurred at different times for different regions, which indicate that the MWP was not a globally uniform event

Possible causes of the MWP include

increased solar activity
decreased volcanic activity and
changes in ocean circulation

Little Ice Age (LIA)

Regional cooling pronounced in North Atlantic Region (Years: ~1300 – 1850)

Paleoclimate proxy records show peak cooling occurred at different times for different regions, which indicate that the LIA was not a globally uniform event

Possible causes of the LIA include

Cyclic lows in solar radiation
increased volcanic activity and
changes in ocean circulation