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| Marine Isotope Stage 8 | |
|---|---|
| Name | Marine Isotope Stage 8 |
| Type | Marine isotope stage |
| Period | Pleistocene |
| Time start | ~300 kyr BP |
| Time end | ~243 kyr BP |
| Preceding | Marine Isotope Stage 9 |
| Following | Marine Isotope Stage 7 |
Marine Isotope Stage 8 is a glacial interval in the Pleistocene identified in deep-sea oxygen isotope records and correlated with terrestrial glacial evidence across Eurasia, North America, and Antarctica. It is recognized in marine isotope stratigraphy used by Milankovitch-inspired paleoclimatology, and it is associated with major changes in ice volume, sea level, and vegetation shown in multiple proxy archives such as foraminifera assemblages, ice cores, and loess sequences.
MIS 8 corresponds to a cold stage characterized by expanded ice sheets, lowered global sea levels, and altered oceanic circulation documented in cores from the North Atlantic, South Atlantic, Indian Ocean, and Pacific Ocean. Interpretations of MIS 8 integrate datasets from the LR04 benthic stack, EPICA, Vostok Glacier, and regional studies in the British Isles, Scandinavia, Siberia, Greenland, and North America. Chronostratigraphic frameworks combine marine isotope stratigraphy with tephrochronology, U-Th dating, and cosmogenic nuclide exposure ages derived from moraines and erratics tied to glacial advances in areas studied by teams from institutions such as the British Geological Survey and the United States Geological Survey.
The timing of MIS 8 is defined within the Marine Isotope Stage nomenclature and commonly placed between approximately 300 and 243 thousand years before present, bounded by interglacials correlated with MIS 9 and MIS 7 as represented in the LR04 stack and tuned to the astronomical timescale of Milankovitch cycles. Boundaries are constrained by correlations among marine records from sites like ODP Site 983 and ODP Site 980, and high-resolution ice-core chronologies from Greenland Ice Sheet Project (GISP2) and Antarctic ice cores that provide oxygen isotope and greenhouse gas context; these correlations are refined using paleomagnetism and regional stratigraphic markers such as Last Interglacial equivalents and tephra layers identified by groups at the University of Copenhagen and University of Cambridge.
Global paleoclimate during this interval featured substantial cooling, reduced polar summer insolation, and reorganized thermohaline circulation evidenced in proxies from the North Atlantic Drift, Antarctic Circumpolar Current, and tropical upwelling zones off Peru and West Africa. Sea-level reconstructions based on coral terraces, oxygen isotopes, and geophysical models indicate fall in global mean sea level by tens of metres relative to interglacial highstands, with estimates refined by studies of raised coral reefs near Bermuda, submerged coastal sediments in Mediterranean basins, and sequence stratigraphy applied by researchers at the Smithsonian Institution and Scripps Institution of Oceanography.
Ice-sheet reconstructions attribute major expansions of the Laurentide Ice Sheet, peripheral advances in the Fennoscandian Ice Sheet, and enhanced growth of the Antarctic Ice Sheet during MIS 8, with outlet glacier behavior inferred from moraine complexes, drumlin fields, and glacial geomorphology in regions mapped by the Geological Survey of Canada and the Norwegian Polar Institute. Ice-sheet dynamics were modulated by bed conditions, ice-stream activity, and marine-terminating margin instability documented in studies integrating seismic reflection data from the North Sea and cosmogenic exposure ages from moraine sequences in Scotland and Alaska.
Proxy archives for MIS 8 include benthic and planktonic foraminiferal δ18O and δ13C records from IODP cores, pollen sequences from lacustrine sediments in the Caucasus and Iberian Peninsula, loess-paleosol successions across China and Central Europe, and speleothem records from caves investigated by teams at the Max Planck Institute for Chemistry and University of Oxford. Regional syntheses draw on data from Lake Baikal, coral reef terraces in the Caribbean, and peat sequences in Scandinavia, with multiproxy comparisons aided by international collaborations such as the PAGES project and regional working groups at the European Geosciences Union.
MIS 8 cooling is principally attributed to orbital forcing following the principles of Milankovitch, particularly minima in summer insolation at high northern latitudes, combined with greenhouse gas reductions observed in Antarctic ice cores from EPICA and Vostok Glacier, and feedbacks involving albedo, dust, and ocean circulation changes in the Atlantic Meridional Overturning Circulation. Additional forcings invoked include variations in volcanic aerosol loads documented by tephra correlations, ice-sheet topography feedbacks explored in coupled climate-ice-sheet models developed at the National Center for Atmospheric Research and MPI for Meteorology, and internal variability linked to modes studied by researchers at the Woods Hole Oceanographic Institution.
During MIS 8, hominin populations in Africa, Europe, and Asia experienced shifts in habitability reflected in archaeological records from Levalloiso-Mousterian and earlier Middle Pleistocene sites, with faunal turnovers evident in mammalian assemblages studied in the Fossil Record of France, Spain, and Kenya. Vegetation changes from palynological records document expansions of steppe, tundra, and cold-adapted biomes affecting megafauna distributions noted in paleontological collections at institutions like the Natural History Museum, London and the Smithsonian National Museum of Natural History.
The recognition of MIS 8 arose from marine oxygen isotope stratigraphy advanced by researchers at Lamont–Doherty Earth Observatory and others refining the LR04 stack; ongoing debates concern the exact phasing of regional glacial advances, the amplitude of sea-level change, and the role of CO2 versus insolation as pacing mechanisms. Outstanding questions include the timing of deglaciation transitions as recorded in cosmogenic nuclide datasets, the sensitivity of ice-sheet margins to ocean forcing as inferred from seismic and sedimentary records, and the integration of archaeological chronologies with paleoclimate datasets pursued by interdisciplinary consortia including the Quaternary Research Association and the International Ocean Discovery Program.