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Stadials and interstadials are phases dividing the Quaternary period, or the last 2.6 million years. Stadials are periods of colder climate while interstadials are periods of warmer climate.
Each Quaternary climate phase is associated with a Marine Isotope Stage (MIS) number, which describe alternation between warmer and cooler temperatures as measured by oxygen isotope data. Stadials have even MIS numbers and interstadials odd MIS numbers. The current Holocene interstadial is MIS 1 and the Last glacial maximum stadial is MIS 2.
Marine Isotope Stages are sometimes further subdivided into stadials and interstadials by minor climate fluctuations within the overall stadial or interstadial regime, which are indicated by letters. The odd-numbered interstadial MIS 5, also known as the Sangamonian interglacial, contains two periods of relative cooling, and so is subdivided into three interstadials (5a, 5c, 5e) and two stadials (5b, 5d). A stadial isotope stage like MIS 6 would be subdivided by periods of relative warming, and so in that case the first and last subdivisions would be stadials; MIS 6a, 6c and 6e are stadials while 6b and 6d are interstadials.
Generally, stadials endure for a thousand years or less, and interstadials for less than ten thousand years, while interglacials last for more than ten thousand and glacials for about one hundred thousand.
While the MIS 1 interstadial encompasses the entirety of the present Holocene interglacial, the Wisconsin glaciation encompasses MIS 2, 3, and 4.
Glacials and Interglacials refer to the 100kyr cycles associated with Milankovitch cycles, while stadials and interstadials are defined by the actual oxygen-isotope temperature record.
The Bølling Oscillation and the Allerød Oscillation, where they are not clearly distinguished in the stratigraphy, are taken together to form the Bølling/Allerød interstadial, and dated from about 14,700 to 12,700 years before the present.
The Oldest, Older, and Younger Dryas are three stadials that occurred during the warming since the Last Glacial Maximum. The Older Dryas occurred between the Bølling and Allerød interstadials. All three periods are named for the arctic plant species, Dryas octopetala, which proliferated during these cold periods.
Greenland ice cores show 24 interstadials during the one hundred thousand years of the Wisconsin glaciation. Referred to as the Dansgaard-Oeschger events, they have been extensively studied, and in their northern European contexts are sometimes named after towns, such as the Brorup, the Odderade, the Oerel, the Glinde, the Hengelo, or the Denekamp.