EAR Test 2

paleoclimate

studies examine changes in Earth’s
climate system through time
• Uses “proxies” of past environments to reconstruct
physical and biological changes related to climate
• Shed light on historic rates and magnitude of climate
change to help understand current and future changes

archives

deposits or settings in which scientists
can find information about past climates

proxies

materials
and/or
properties
contained in
archives that
we use to infer
past climate

Bedload

rolling,
sliding, and saltation

Suspended load

floating fine-grained
particles

Dissolved load

individual ions

Rainfall, wind, and ice erode rock and transport material in…

…granular and dissolved forms

Biological proxies example

What was living at the time the sediment was deposited?

Foraminifera

calcite shell-bearing organisms

Diatoms

silica shell-bearing organisms

Geochemical proxy example

Texture of sediment

ocean crust is recycled…

…subduction

Sensitivity test

altering one boundary
condition at a time to reveal the individual
impact of each variable on the system

Much of the paleoclimate information we have
from the past ~170 Ma…

…is from ocean cores

On continents, lake sediments…

are excellent archives of paleoclimate

Contain both biological and geochemical proxies

Most lake sediment records com from…

… the Northern Hemisphere

Proxy

their chemistry can tell us
about past climate changes

Speleothems

layers formed drop-by-drop from rainwater absorbing Co2 from soil and limestone absorbing rainwater

Tree ring proxies

Total ring width
• Earlywood width (spring/summer)
• Latewood width (fall)
• Density of rings
• Composition (carbon and oxygen)
• Damage (frost, fire, insects)

Corals also have…

…have annual banding, which can tell us about fluctuations in
ocean conditions (including temperature)

Phenology

timing of leaf out (in fall) and flowering (in spring)

tephras

Volcanic eruptions leave ash
deposits in sediments and ice

radioactive

this means that the isotope is
unstable, and will eventually lose a particle

parent isotope

original, non radioactive isotope

daughter isotope

isotope after loosing particle

rate of decay

the ratio of daughter
to parent to determine the age

Half-life

time needed for half
of the parent isotopes to decay
to the daughter isotopes

Climate Models

Represent the
atmosphere and ocean
system as grid cells
• Move fluxes of water,
mass, and energy
between these grid cells
• More complex models
have ecosystem gas
fluxes from ocean and
land

Control run

simulation of the present-day climate
• Test if the model does a good job!

Boundary conditions

the input to the model used to drive the
climate system
• Example – position of continents, ice sheets, sea-level, etc

Experimental run

perturb some aspect of the climate system in
the mode (alter greenhouse gases, solar radiation, etc)

test against geologic record:

see if existing paleodata support
the model

acid

A solution with a high concentration of hydrogen ions,

that is, with a pH less than 7.

Anion

A negatively charged ion.

Base

A solution with a low concentration of hydrogen ions,

that is, with a pH greater than 7.

Biological pump

A transfer of C02 and nutrients from the surface

waters to the deep ocean as a result of photosynthesis in shallow

waters, of the settling of organic matter, and of decomposition in

deep waters. This process operates on a much faster time scale (days

to months) than the thermohaline circulation of the oceans.

Biological sulfate reduction A metabolic pathway in w

Biomass

The total combined weight of organic material in each

trophic level. In terrestrial ecosystems the biomass is reduced by

90 to 99% at each higher trophic level.

Biosphere

The part of the Earth system that directly supports

life, including the oceans, atmosphere, land surface, and soils.

Carbonate metamorphism

A chemical reaction occurring at

high temperatures and pressures between sedimentary carbonate

minerals and silica-rich sediments that forms calcium silicate

ruinerals and releases C02.

Cation

A positively charged ion.

characteristic response time

How long a reservoir takes to

respond measurably to large imbalances in inflow or outflow, calculated

in the same way as residence time.

Coal

A hydrogen- and carbon-bearing compound produced

under high-pressure and high-temperature conditions of burial

deep within the solid Earth; a fossil fuel formed from high concentrations

of organic matter in terrestrial sediments.

Consumers

Organisms, such as animals, that are incapable of

utilizing solar energy directly but must instead consume plants or

other photosynthesizers to utilize the chemical energy stored in

plant tissues.

Denitrification

The conversion of fixed nitrogen into N2 or

NzO by bacteria.

Fixed nitrogen

Compounds containing a nitrogen atom bonded

to something other than another nitrogen atom.

Inorganic carbon

Carbon not associated with compounds that

are typically formed by living organisms and that do not contain

carbon-carbon or carbon-hydrogen bonds.

Limestone

A sedimentary rock composed largely of calcium

carbonate minerals, mainly calcite.

Methanogenesis

Methane production carried out by certain

bacteria.

Nitrogenase

An enzyme used by nitrogen-fixing organisms to

convert N2 into fixed nitrogen.

Nutrient

Substances normally obtained in the diet that are

essential to organisms.

Organic carbon

Carbon associated with compounds that are

typically formed by living organisms and that contain carboncarbon

or carbon-hydrogen bonds.

oxidized carbon

Carbon that, in compounds, is combined

with oxygen. The carbon atoms in skeletons composed of CaC03

and in atmospheric C02 are oxidized carbon.

Petroleum

A hydrogen- and carbon-bearing compound produced

under high-temperature conditions of burial deep (3-4 km)

within the crust; afossilfuel formed from high concentrations of

organic matter in marine sediments.

Photic zone

The portion of the oceans where there is sufficient

sunlight for photosynthesis; about the upper 100 m of the water

column.

pH

A measure of acidity, defined as the negative logarithm (to

the base 10) of the hydrogen ion concentration (in moles per

liter). Acids have pH values less than 7, and bases have pH values

greater than 7. A pH of 7 is defined as neutral.

Photosynthesis

The process by which an organism such as a

green plant uses sunlight, carbon dioxide, and water to produce

organic matter and oxygen.

Primary producer

A plant (or other type of photosynthesizer

or chemosynthesizer) that provides energy used by consumers.

Primary productivity

The amount of organic matter produced

by photosynthesis in a unit time over a unit area of Earth's surface;

also called productivity.

Redfield ratio

The ratios of the nutrient elements that marine

organisms incorporate into their tissues; these ratios appear

to be nearly identical in all species of photoplankton. For these

organisms, the atomic ratio of carbon:nitrogen:phosphorus is

very nearly 106:16:1.

Reduced carbon

Carbon that, in compounds, is combined

mainly with other carbon atoms, hydrogen, or nitrogen; organic

carbon is a form of reduced carbon. Reduced carbon tends to be

reactive in the presence of oxygen gas.

Residence time

The average length of time a substance spends

in a given reservoir that is at a steady state with respect to the

processes that add and remove the substance to and from the reservoir.

Residence time is calculated as the ratio of the reservoir size

to the rate of inflow or outflow (which are equal at steady state).

Steady state

A condition in which the state of a system component

is unchanging in time. A reservoir is in steady state when the

rates of inflow and outflow are equal

Zooplankton

Free-floating, marine consumers, including

small invertebrates and microorganisms that cannot photosynthesize

and therefore feed on phytoplankton.

continental crust

A layer of rock averaging 30 km thick,
having the composition of granite, that constitutes the
continents.

Ocean crust

5–10 kilometers thick, has an
average composition like that of basalt, and is higher
in density (3.2 g/cm 3
).

Mantle

richer in heavy ele-
ments like iron (Fe) and magnesium (Mg) and has
an even higher density (> 3.6 g/cm3
). The mantle
extends 2,890 kilometers into Earth’s interior, almost
halfway to its center at a depth of 6,370 kilometers.

Lithosphere

Earth’s rigid outer rocky shell, made of the crust and the solid outer part of the upper mantle. It extends to a depth of about 60 miles (100 km) and is broken into separate tectonic plates

astenosphere

• A zone of the earth's mantle that lies beneath the lithosphere and consists of several hundred kilometers of deformable rock.

• The lower layer of the earth's crust, below the lithosphere. It is estimated as from fifty to several hundred miles thick. It is less rigid than the lithosphere, but still rigid enough to transmit some transverse seismic waves.

technonic plates

massive slabs of solid rock made of Earth’s lithosphere (crust plus upper mantle) that move slowly over time. They range from a few hundred to thousands of kilometers across, and their boundaries are where much earthquake and volcanic activity happens.

divergent margins

tectonic plate boundaries where two plates move away from each other, leading to the formation of new oceanic crust as magma rises from the mantle. This process often occurs at mid-ocean ridges, such as the Mid-Atlantic Ridge

convergent margins

areas where tectonic plates move toward each other, often leading to one plate being forced beneath another in a process called subduction. This interaction can result in significant geological activity, including earthquakes and volcanic eruptions.

subduction

A geologic process in which one edge of one crustal plate is forced below the edge of another.

Continental collision

a geological process where two continental plates converge, leading to significant crustal thickening and the formation of mountain ranges, such as the Himalayas from the collision of the Indian and Eurasian plates. This process occurs over millions of years and involves the destruction of subduction zones, resulting in the crumpling and uplifting of the crust.

Transform fault margins

boundaries where tectonic plates slide past each other horizontally, without creating or destroying crust. A well-known example is the San Andreas Fault in California, which connects different tectonic features and is characterized by lateral movement

magnetic field

a vector field near a magnet, electric current, or changing electric field where magnetic forces can be observed. It is often shown with magnetic field lines (flux) and is measured in teslas (T).

Paleomagnetism

the study of ancient Earth's magnetic fields recorded in rocks and sediments, which helps scientists understand the history of plate tectonics and the movement of continents over time. It involves analyzing the magnetic properties of rocks to determine their formation and the orientation of the Earth's magnetic field at that time.

magnetic lineations

patterns of magnetic anomalies on the Earth's surface, which are often associated with the movement of tectonic plates and the history of the Earth's magnetic field. These lineations can indicate the age of oceanic crust and help in understanding plate tectonics and geological processes.

Seafloor spreading

the process where new oceanic crust forms along mid-ocean ridges and then spreads out laterally as it cools. It was proposed in 1960 by geophysicist Harry H. Hess and is a key part of plate tectonics.

polar position hypothesis

suggests that the latitudinal position of continents influences their climate, particularly regarding glaciation; ice sheets are expected to form on continents located at polar or near-polar latitudes. This hypothesis is part of the explanation for Earth's glaciation history but does not account for all variations in climate over time

Gondwana

a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia, Zealandia, Arabia, and the Indian subcontinent.

Pangea

a supercontinent that existed during the late Paleozoic and early Mesozoic eras, forming from earlier landmasses about 335 million years ago and beginning to break apart around 175–200 million years ago. It was surrounded by a global ocean called Panthalassa

evaporites

water-soluble sedimentary mineral deposits formed by the evaporation of water, leading to the concentration and crystallization of minerals. They typically occur in arid environments where evaporation exceeds water inflow, resulting in deposits like halite (rock salt) and gypsum

red beds

sedimentary rocks, typically consisting of sandstone, siltstone, and shale, that are predominantly red in color due to the presence of ferric oxides.

spreading rate
hypothesis

suggests that the rate at which new oceanic crust is formed at mid-ocean ridges influences geological processes, including volcanic activity and the release of carbon dioxide. This hypothesis is linked to the concept of seafloor spreading, where tectonic plates move apart, affecting the Earth's climate over millions of years.

hot spots

are volcanic areas thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. As tectonic plates move over a hotspot, they can form a chain of volcanoes, with volcano ages getting progressively older away from the hotspot.

mass wasting

also known as mass movement, refers to the downhill movement of soil, rock, and debris due to the force of gravity. It can occur suddenly, like landslides, or gradually, such as soil creep, and is influenced by factors like water, slope steepness, and vegetation.

Cretaceous

a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas.a geological period that lasted from about 143.1 to 66 Ma (million years ago).

Warm saline bottom water

water masses that are warmer than typical bottom water, which is usually cold and dense. This type of water can occur due to the intrusion of warmer water masses, affecting the overall circulation and characteristics of bottom water in oceanic environments.

CO2 saturation

As CO2 concentrations rise, the atmosphere gradually
reaches the point at which further CO 2 increases have
little effect in trapping additional back radiation from
Earth’s surface.

transgressions

the rise of sea levels over land, leading to the flooding of coastal areas and the deposition of marine sediments.

regressions

a geological process occurring when areas of submerged seafloor are exposed during a drop in sea level.

eustatic state level

the global average sea level

thermal expansion coefficient

a measure of how much a material expands or contracts when its temperature changes, typically expressed as the change in length per degree of temperature change. Different materials have different coefficients, with metals generally having values between 10 to 30 x 10⁻⁶/K.

hypsometric
curve

a graph showing the proportion of land area at different elevations, plotted as relative area versus relative height. On a hypsometric curve for the whole Earth, there are two maxima of frequencies at 100 m and 4,700 m.

methane clathrate

a solid “ice-like” material where methane gas is trapped inside a crystal structure made of water. It is found under ocean sediments (about 1100 m below the sea surface) and can release methane gas when temperatures increase.

permafrost

soil or underwater sediment which continuously remains below 0 °C for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years.

fractionation

the partitioning of isotopes between two compounds or phases during physical and chemical processes, resulting in different ratios of heavy to light isotopes. It occurs due to isotope exchange reactions and kinetic processes, leading to deviations from equilibrium that are influenced by temperature and reaction rates.

Monterey hypothesis

a major increase in coastal upwelling, per-
haps driven by stronger winds caused by long-term climate
cooling, buried enough organic carbon along the margins of
the Pacific to reduce atmospheric CO2, cool global climate,
and allow ice to build up on Antarctica

equilibrium line

the elevation on a glacier where snow and ice accumulation equals the amount lost from melting and sublimation. Above it is the accumulation zone, and below it is the ablation zone (so its position helps show whether a glacier is growing or shrinking).

Milankovitch theory

says long-term changes in Earth’s orbit and tilt change how much solar energy (insolation) reaches the planet, which helps pace the timing of glacial and interglacial periods (ice ages). It’s mainly driven by three cycles: eccentricity, obliquity, and precession.