Marine Isotope Stage 2

Marine Isotope Stage 2
Name	Marine Isotope Stage 2
Other names	Last Glacial Maximum (part), LGM
Start	~29,000 years BP
End	~14,000 years BP
Period	Late Pleistocene
Notable locations	Laurentide Ice Sheet, Fennoscandian Ice Sheet, Patagonian Ice Sheet

Marine Isotope Stage 2 is a late Pleistocene cold interval traditionally spanning roughly 29,000–14,000 years before present that includes the Last Glacial Maximum and major continental ice-sheet expansions. It is defined in the marine oxygen isotope record and is correlated with terrestrial records from glacial deposits, loess sequences, and speleothems across regions such as North America, Europe, Asia, and the Southern Hemisphere. Researchers link this interval to well-dated stratigraphic markers used in studies by institutions like the British Geological Survey, Lamont–Doherty Earth Observatory, and the Max Planck Institute.

Definition and chronology

Marine Isotope Stage 2 is identified in benthic and planktonic oxygen isotope stacks derived from cores collected by programs such as the Integrated Ocean Drilling Program, Ocean Drilling Program, and Deep Sea Drilling Project, and is tied to radiometric frameworks developed by laboratories at Columbia University, University of Cambridge, and ETH Zurich. Chronologies for the interval draw on calibration against radiocarbon chronologies produced by the University of Groningen and accelerator mass spectrometry facilities at Lawrence Livermore National Laboratory, and are tuned to astronomical solutions by Milanković researchers following work by Berger and Loutre and the astronomical timescales used at the Institut de Physique du Globe de Paris. Boundary definitions are synchronized with ice-core timelines from the Greenland Ice Sheet Project and Antarctic projects such as EPICA and Vostok.

Paleoclimate and global ice extent

During this interval, global climate proxies indicate colder sea-surface temperatures and expanded ice sheets, with ice-sheet reconstructions mapping the Laurentide Ice Sheet, Eurasian Ice Sheet, and West Antarctic Ice Sheet at their maxima in reconstructions published by NASA, USGS, and the Norwegian Polar Institute. Sea-level reconstructions by the University of Hawaii and University of New South Wales show minima that exposed continental shelves such as the Bering Land Bridge and Sahul Shelf, affecting ocean circulation systems studied by Scripps Institution of Oceanography and the Woods Hole Oceanographic Institution. Atmospheric circulation shifts inferred from Greenland ice cores, Speleothem records from the Max Planck Institute and isotope-enabled Earth system models from NCAR demonstrate changes in the Atlantic Meridional Overturning Circulation linked to Heinrich events documented in North Atlantic marine records.

Regional expressions and proxy records

In North America, glacial geomorphology documented by the U.S. Geological Survey and Canadian Geological Survey records the lobate margins of the Laurentide Ice Sheet, while loess deposits studied at the Chinese Academy of Sciences and loess–paleosol sequences in Europe recorded by the Geological Survey of Finland preserve aeolian signals. Marine sediment cores from the North Atlantic collected by the Alfred Wegener Institute, sedimentary sequences from the Mediterranean studied by the Consiglio Nazionale delle Ricerche, and foraminifera assemblages analyzed by the Smithsonian Institution provide regional sea-surface temperature reconstructions. Southern Hemisphere expressions are informed by pollen records at the Australian National University, glacier chronologies in Patagonia by the Universidad de Magallanes, and ice-core isotopes from the British Antarctic Survey.

Causes and forcings

Forcing mechanisms invoked include orbital forcing quantified by astronomers at Observatoire de Paris, greenhouse gas concentration changes recorded in ice cores by the National Oceanic and Atmospheric Administration and Scripps Institution of Oceanography, and ice-sheet dynamics modeled by teams at the University of Bristol and Potsdam Institute for Climate Impact Research. Feedbacks involving albedo effects tied to ice extent mapped by the European Space Agency, dust radiative forcing evidenced in Antarctic cores analyzed by the Alfred Wegener Institute, and ocean circulation feedbacks represented in simulations by the Geophysical Fluid Dynamics Laboratory are all implicated. Episodic meltwater pulses associated with proglacial lakes studied by the University of Minnesota and catastrophic drainage events reconstructed by researchers at the University of Toronto have been proposed as triggers for abrupt climatic shifts within the interval.

Human and ecological impacts

Human populations across regions such as Europe, Siberia, Beringia, and Australia (research led by institutions including the Max Planck Institute for Evolutionary Anthropology, Australian National University, and University of Alaska Fairbanks) experienced range contractions, technological adaptations, and migratory responses evident in archaeological records curated by the British Museum, Smithsonian Institution, and National Museum of Denmark. Megafaunal changes documented in paleontological collections at the Natural History Museum, Los Angeles County Museum of Natural History, and Museo Nacional de Ciencias Naturales correlate with vegetational shifts reconstructed from pollen archives at Wageningen University and the University of Göttingen. Coastal and marine ecosystems altered by sea-level lowstands influenced human foraging zones documented in shell midden records held by the University of Cape Town and Museo de La Plata.

Research methods and key sites

Key research methods include oxygen isotope stratigraphy developed from cores by the Ocean Drilling Program, radiocarbon dating advances at the University of Oxford Radiocarbon Accelerator Unit, luminescence dating applied by the University of Melbourne, and cosmogenic nuclide exposure dating pioneered by Columbia University and ETH Zürich. Prominent study sites include North Atlantic cores from the Iceland Basin, Antarctic ice cores from EPICA Dome C, Laurentide deglacial sequences in the Hudson Highlands, speleothem records from Soreq Cave, loess sections in the Chinese Loess Plateau, and Patagonian glacier moraine chronologies at Lago Argentino. Collaborative networks such as PAGES, INQUA, and CLIVAR coordinate multinational field campaigns and synthesis efforts that continue to refine the temporal and spatial understanding of this glacial interval.

Category:Late Pleistocene