Marine isotopic stage
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Marine isotopic stages (MIS) are alternating warm and cool periods in the Earth's palaeoclimate, deduced from oxygen isotope data reflecting temperature curves derived from data from deep sea core samples.
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[edit] The significance of the data
Each stage is a period of higher or lower temperature on a graph of mean temperature (y-axis) versus millions, hundreds of thousands or thousands of years (x-axis). The cycles were found to correspond to terrestrial evidence of glacials and interglacials. A graph of the entire series of stages then revealed hitherto unknown and unsuspected advances and retreats of ice and also filled in the details of the stadials and interstadials. More recent core samples of today's glacial ice substantiated the cycles through studies of ancient pollen deposition. Currently a number of methods are making additional detail possible.
[edit] The number of stages
Each stage represents a glacial, interglacial, stadial or interstadial. Interglacials are odd-numbered; glacials are even numbered, one for each stage, starting from the present and working backward in time. For example, the Holocene is MIS1, or O-stage 1, or just stage 1. The previous interglacial is MIS5, or O-stage 5, or just stage 5.
Exceptionally, MIS2-4 refer to the last glacial, because when initially interpreted MIS3 looked like an interglacial.
Stadials and interstadials are identified by a letter following the corresponding glacial or interglacial: 5a, 5b, etc. The dates of the stages were obtained by calibrating the graph on known dates by other methods.
MIS 11 of approximately 400ka is the most similar to MIS 1. The difference that has puzzled scientists is the current rise in CO2 levels of MIS1, which according to natural trends based on past interglacials should have been steadily decreasing over the last 5000y.
[edit] Matching the stages to named periods
Matching the stages to named periods proceeds as new dates are discovered and new regions are explored geologically. Currently a timeline of glaciation for the Plio-Pleistocene exists and is finding its way gradually into ice age literature.
