Global Cycles, Paleoceanography, and Human Impacts

Global Biogeochemical Cycle

The complete pathway that a chemical element of compound follws through the Earth’s four major resevoirs, often returning to the starting point.

6 Key Nutrients for Life

Carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulphur.

Box Model

A simple graphical representation of a biogeochemical cycle. Includes flux: how much material is transferred between reservoirs and how fast, reservoirs: where and how much material (concentration) is stored and for how long, and pathways of transfer and processes controlling transfer.

Whole Earth Global Cycles

Closed systems which maintain mass balance.

Dynamic Equilibrium

Opposing processes in global cycles maintain a balanced state.

Forcing Event

Initial push within one part of the system that causes the system to temporarily move away from dynamic equilibrium. Opposing processes need time to adjust to a new equilibrium stat and maintain balance.

Tipping Point

A critical threshold in the Earth system where a small push can trigger rapid, dramatic change.

Carbon

The foundation for life and on of the essential major nutrients for life, exchanges between all four of Earth’s main systems, most is stored in the geosphere.

Residence Time

The amount of time a material spends in a particular reservoir, depends on size and flux rates.

Carbon Sinks

Reservoirs that collect and store carbon, of special interest due to anthropogenic rise in greenhouse gas concentration in the atmosphere.

Great Oxidation Event

The period in Earth’s history when the atmosphere began to transform from reducing to oxidizing, occurring about 2.4 billion years ago. Only reaching present day levels around 600 million years ago.

Ferruginous

Describes Archean oceans which were dominant in reduced Fe(II), which is very soluble, with high iron concentrations in the seawater.

Sulphidic

Describes oceans after the great oxygenation events, characterized by increased sulfur concentrations due to weathering of high-sulfur reduced minerals, high delivery of sulphate to oceans, and microbial use of sulphate as an oxidizing agent for respiration, producing an H₂S byproduct.

Paleoceanography

The study of the physical, chemical, and biological state of past oceans, closely linked to paleoclimatology because the oceans, atmosphere, and climate are inter-connected.

Sediment Archives

sediments making up the seafloor which respond to and preserve past oceanographic changes. Include cosmogenic, lithogenic, authigenic, and biogenic sediments.

Sediment Proxies

A measurable property of a sedimentary archive that responds to changes in the marine environment in clear and predictable ways. Indirectly describe “target parameters” that characterize the physical, chemical, and biological stat of the past oceans because they cannot be measured directly in the sediments. Must be calibrated in the modern ocean before they can be applied to the reconstruction of pas ocean environments.

Ocean Temperature Proxy

Assemblages and magnesium/carbon ratios in foraminifera.

Ocean Circulation Proxy

Nd isotopes of Iron-manganese crusts.

Asteroid Ejecta Proxy

Ir in clay and organic-rich sediment

Quaternary Period

A period in Earth’s history which began 2.58 million years ago when permanent ice sheets formed in the northern hemisphere and contains our current glacial-interglacial climate regime.

Quaternary Climate Reconstruction

Proxies based on ¹⁸O/¹⁶O and Mg/ca records of foraminifera allow changes in ice sheet volume (sea level) and ocean temperature to be reconstructed. Showing that glacial-interglacial climate change is paced by Earth’s orbital cycles, also providing a timescale for reconstructions.

Phanerozoic Eon

An eon in earth’s history (after about 540 mya) which was dominated by warm, greenhouse climates that were ice-free. This includes early cenozoic until the late Cenozoic (~66 to ~32 mya)

Late Cenozoic

The period in Earth’s history (the last ~32 mya) characterized by global cooling and the growth of polar ice sheets leading up to the Quaternary ice age and glacial-interglacial climate regime.

Reconstruction Timescales

Assigned using Earth’s orbitally-driven solar radiation cycles, magnetostratigraphy, biostratigraphy, and radiometric dating.