Marine isotope stage - AbsoluteAstronomy.com

Marine isotope stages marine oxygen-isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data

Oxygen isotope ratio cycle

Oxygen isotope ratio cycles are cyclical variations in the ratio of the abundance of oxygen with an atomic mass of 18 to the abundance of oxygen with an atomic mass of 16 present in some substances, such as polar ice or calcite in ocean core samples. The ratio is linked to water temperature of...

reflecting changes in temperature derived from data from deep sea core sample

Core sample

A core sample is a cylindrical section of a naturally occurring substance. Most core samples are obtained by drilling with special drills into the substance, for example sediment or rock, with a hollow steel tube called a core drill. The hole made for the core sample is called the "core hole". A...

s. The data is derived from pollen

Pollen

Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...

and foraminifera

Foraminifera

The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

(plankton

Plankton

Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

) remains in drilled marine sediment

Sediment

Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

cores, sapropel

Sapropel

Sapropel is a term used in marine geology to describe dark-coloured sediments that are rich in organic matter...

s, and other data that reflect historic climate; these are called proxies

Proxy (climate)

In the study of past climates is known as paleoclimatology, climate proxies are preserved physical characteristics of the past that stand in for direct measurements , to enable scientists to reconstruct the climatic conditions that prevailed during much of the Earth's history...

. The MIS timescale was developed from the pioneering work of Cesare Emiliani

Cesare Emiliani

Cesare Emiliani was an Italian-American scientist, considered one of the greatest geologists and micropaleontologists of the 20th century and the founder of paleoceanography, developing the timescale of marine isotope stages, which despite modifications remains in very wide use today.He...

in the 1950s, and is now widely used in archaeology

Archaeology

Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...

and other fields to express dating in the Quaternary

Quaternary

The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...

period (the last 2.6 million years), as well as providing the fullest and best data for that period for paleoclimatology

Paleoclimatology

Paleoclimatology is the study of changes in climate taken on the scale of the entire history of Earth. It uses a variety of proxy methods from the Earth and life sciences to obtain data previously preserved within rocks, sediments, ice sheets, tree rings, corals, shells and microfossils; it then...

or the study of the early climate of the earth, representing "the standard to which we correlate other Quaternary climate records". Emiliani's work in turn depended on Harold Urey

Harold Urey

Harold Clayton Urey was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934...

's prediction in a paper of 1947 that the ratio between oxygen-18

Oxygen-18

Oxygen-18 is a natural, stable isotope of oxygen and one of the environmental isotopes.18O is an important precursor for the production of fluorodeoxyglucose used in positron emission tomography...

and oxygen-16 isotopes in calcite

Calcite

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...

, the main chemical component of the shells and other hard parts of a wide range of marine organisms, should vary depending on the prevailing water temperature in which the calcite was formed.

Working backwards from the present, MIS 1 in the scale, stages with even numbers have high levels of oxygen-18 and represent cold glacial periods, while the odd-numbered stages are troughs in the oxygen-18 figures, representing warm interglacial

Interglacial

An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...

intervals. Over 100 stages have been identified, going currently back some 6 million years, and the scale may in future reach back up to 15 mya. Some stages, in particular MIS 5, are divided into sub-stages, such as "MIS 5a", with 5 a, c, and e being warm and b and d cold. A numeric system for referring to "horizons" (events rather than periods) may also be used, with for example MIS 5.5 representing the peak point of MIS 5e, and 5.51, 5.52 etc representing the peaks and troughs of the record at a still more detailed level. For more recent periods, increasingly precise resolution of timing continues to be developed.

Developing a timescale

In 1957 Emiliani moved to the University of Miami

University of Miami

The University of Miami is a private, non-sectarian university founded in 1925 with its main campus in Coral Gables, Florida, a medical campus in Miami city proper at Civic Center, and an oceanographic research facility on Virginia Key., the university currently enrolls 15,629 students in 12...

to have access to core-drilling ships and equipment, and began to drill in the Caribbean

Caribbean

The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

and collect core data. A further important advance came in 1967, when Nicholas Shackleton

Nicholas Shackleton

Sir Nicholas John Shackleton FRS was a British geologist and climatologist who specialised in the Quaternary Period...

suggested that the fluctuations over time in the marine isotope ratios that had then become evident were caused not so much by changes in water temperature, as Emiliani thought, but mainly by changes in the volume of ice-sheets, which when they expanded took up the lighter oxygen-16 isotypes in preference to the heavier oxygen-18. The cycles in the isotope ratio were found to correspond to terrestrial evidence of glacials and interglacials. A graph of the entire series of stages then revealed unsuspected advances and retreats of ice and also filled in the details of the stadials and interstadials

Stadial

A stadial is a period of lower temperatures during an interglacial separating the glacial periods of an ice age. Such periods are of insufficient duration or intensity to be considered glacial periods...

. More recent ice core

Ice core

An ice core is a core sample that is typically removed from an ice sheet, most commonly from the polar ice caps of Antarctica, Greenland or from high mountain glaciers elsewhere. As the ice forms from the incremental build up of annual layers of snow, lower layers are older than upper, and an ice...

samples of today's glacial ice substantiated the cycles through studies of ancient pollen

Pollen

deposition. Currently a number of methods are making additional detail possible. Matching the stages to named periods proceeds as new dates are discovered and new regions are explored geologically. The marine isotopic records appear more complete and detailed than any terrestrial equivalents, and have enabled a timeline of glaciation

Timeline of glaciation

There have been five known ice ages in the Earth's history, with the Earth experiencing the Quaternary Ice Age during the present time. Within ice ages, there exist periods of more severe glacial conditions and more temperate referred to as glacial periods and interglacial periods, respectively...

for the Plio

Pliocene

The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

-Pleistocene

Pleistocene

The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

to be identified. It is now believed that changes in the size of the major ice sheet

Ice sheet

An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...

s such as the historical Laurentide ice sheet

Laurentide ice sheet

The Laurentide Ice Sheet was a massive sheet of ice that covered hundreds of thousands of square miles, including most of Canada and a large portion of the northern United States, multiple times during Quaternary glacial epochs. It last covered most of northern North America between c. 95,000 and...

of North America are the main factor governing variations in the oxygen isotope ratios.

The MIS data also matches the astronomical data of Milankovitch cycles

Milankovitch cycles

Milankovitch theory describes the collective effects of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković, who worked on it during First World War internment...

of orbital forcing

Orbital forcing

Orbital forcing is the effect on climate of slow changes in the tilt of the Earth's axis and shape of the orbit . These orbital changes change the total amount of sunlight reaching the Earth by up to 25% at mid-latitudes...

or the effects of variations in insolation

Insolation

Insolation is a measure of solar radiation energy received on a given surface area in a given time. It is commonly expressed as average irradiance in watts per square meter or kilowatt-hours per square meter per day...

caused by cyclical slight changes in the tilt of the earth's axis of rotation - the "orbital theory". Indeed that the MIS data matched Milankovich's theory, which he formed during World War I, so well was a key factor in the theory gaining general acceptance, despite some remaining problems at certain points, notably the so-called 100,000-year problem

100,000-year problem

The 100,000-year problem is a discrepancy between past temperatures and the amount of incoming solar radiation, or insolation. The former rises and falls according to the strength of radiation from the sun, the distance from the earth to the sun, and the tilt of the Earth's poles...

. For relatively recent periods data from radiocarbon dating and dendrochronology

Dendrochronology

Dendrochronology or tree-ring dating is the scientific method of dating based on the analysis of patterns of tree-rings. Dendrochronology can date the time at which tree rings were formed, in many types of wood, to the exact calendar year...

also support the MIS data. The sediments also acquire depositional remanent magnetization which allows them to be correlated with earth's geomagnetic reversal

Geomagnetic reversal

A geomagnetic reversal is a change in the Earth's magnetic field such that the positions of magnetic north and magnetic south are interchanged. The Earth's field has alternated between periods of normal polarity, in which the direction of the field was the same as the present direction, and reverse...

s. For older core samples, individual annual depositions cannot usually be distinguished, and dating is taken from the geomagnetic information in the cores. Other information, especially as to the ratios of gases such as carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

in the athmosphere, is provided by analysis of ice core

Ice core

s.

The SPECMAP Project, funded by the US National Science Foundation

National Science Foundation

The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...

, has produced one standard chronology for oxygen isotope records, although there are others. This high resolution chronology was derived from several isotopic records, the composite curve was then smoothed, filtered and tuned to the known cycles of the astronomical variables. The use of a number of isotopic profiles was designed to eliminate 'noise' errors, that could have been contained within a single isotopic record. Another large research project funded by the US government in the 1970s and 1980s was Climate: Long range Investigation, Mapping, and Prediction

Climate: Long range Investigation, Mapping, and Prediction

Climate: Long range Investigation, Mapping, and Prediction, known as CLIMAP, was a major research project of the 1970s and 80s to produce a map of climate conditions during the last glacial maximum...

or CLIMAP, which to a large degree succeeded in its aim of producing a map of the global climate at the Last Glacial Maximum

Last Glacial Maximum

The Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...

, some 18,000 years ago, with some of the research also directed at the climate some 120,000 years ago, during the last interglacial. The theoretical advances and greatly improved data available by the 1970s enabled a "grand synthesis" to be made, best known from the 1976 paper Variations in the earth’s orbit: pacemaker of the ice ages (in Science
Science (journal)
Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....

), by J.D. Hays, Shackleton and John Imbrie

John Imbrie

John Imbrie is an American paleoceanographer best known for his work on the theory of ice ages.After serving with the 10th Mountain Division in Italy during World War II, Imbrie earned his bachelor's degree from Princeton University. He then went on to receive a Ph.D. from Yale University in 1951...

, which is still very widely accepted today, and covers the MIS timescale and the causal effect of the orbital theory.

Stages

The following are the start dates of the most recent MIS, in kya (thousands of years ago). The first figures are derived by Aitken & Stokes from Bassinot et al. (1994), with the figures in parentheses alternative estimates from Martinson et al. for stage 4 and for the others the SPECMAP figures in Imbrie et al. (1984). For stages 1-16 the SPECMAP figures are within 5 kya of the figures given here. All figures up to MIS 21 are taken from Aitken & Stokes, Table 1.4, except for the sub-stages of MIS 5, which are from Wright's Table 1.1.

MIS 1 - 11 kya, end of the Younger Dryas
Younger Dryas
The Younger Dryas stadial, also referred to as the Big Freeze, was a geologically brief period of cold climatic conditions and drought between approximately 12.8 and 11.5 ka BP, or 12,800 and 11,500 years before present...

marks the start of the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

, continuing to the present
MIS 2 - 24 near Last Glacial Maximum
Last Glacial Maximum
The Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...
MIS 3 - 60
MIS 4 - 71 (74)
MIS 5 - 130, includes the Eemian; usually sub-divided in a to e:
- MIS 5a - 84.74
- MIS 5b - 92.84
- MIS 5c - 105.92
- MIS 5d - 115.105
- MIS 5e - 130.115
MIS 6 - 190
MIS 7 - 244
MIS 8 - 301
MIS 9 - 334
MIS 10 - 364
MIS 11 427, the most similar to MIS 1.
MIS 12 - 474
MIS 13 - 528
MIS 14 - 568
MIS 15 - 621
MIS 16 - 659
MIS 17 - 712 (689)
MIS 18 - 760 (726)
MIS 19 - 787 (736)
MIS 20 - 810 (763)
MIS 21 - 865 (790)

Some older stages, in mya (millions of years ago):

MIS 22 - 1.03 mya, marking the end of the Bavelian period in Europe
MIS 62 - 1.75, end of the Tiglian
MIS 103 - 2.588, end of the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

and start of the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

, on the INQUA time scale (older definitions put this change at 1.806 mya - the MIS date is unaffected)

External links

Marine Isotope Substage 5e and the Eemian Interglacial, NJ Shackleton, 2003
650,000 years of greenhouse gas concentrations, RealClimate, 2005
Glacial variability over the last two million years, P Huybers, 2007
The polar paleoclimate signature of Marine Isotope Stage 31, Reed Scherer, 2007
Oceanic forcing of the Marine Isotope Stage 11 interglacial, Alexander J. Dickson , Christopher J. Beer , Ciara Dempsey , Mark A. Maslin , James A. Bendle , Erin L. McClymont & Richard D. Pancost, 2009
Last Time Carbon Dioxide Levels Were This High: 15 Million Years Ago, Aradhna Tripati, 2009
US NCDC
NASA SPECMAP

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Developing a timescale

Stages

See also

External links