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TitleThe Last Glacial Maximum
AuthorClark, P U; Dyke, A S; Shakun, J D; Carlson, A E; Clark, J; Wohlfarth, B; Mitrovica, J X; Hostetler, S W; McCabe, A M
SourceScience vol. 325, no. 5941, 2009 p. 710-714,
LinksSupplementary Data
Alt SeriesEarth Sciences Sector, Contribution Series 20080591
PublisherAmerican Association for the Advancement of Science (AAAS)
Mediapaper; on-line; digital
File formathtml; pdf (Adobe® Reader®)
AreaArctic; Antarctic; North America; Europe; Tibet; Tropics; Sub-Tropics; Southern Hemisphere
Lat/Long WENS-180.0000 180.0000 90.0000 -90.0000
Subjectssurficial geology/geomorphology; environmental geology; Pleistocene; Holocene; geological history; glacial history; glaciation; deglaciation; climate; climatic fluctuations; climatology; radiometric dating; helium isotopes; carbon isotopes; glaciers; ice sheets; sea level changes; Cordilleran Ice Sheet; Innuitian Ice Sheet; Laurentide Ice Sheet; West Antarctic Ice Sheet; East Antarctic Ice Sheet; Antarctic Peninsula Ice Sheet; Barents-Kara Ice Sheet; Greenland Ice Sheet; British-Irish Ice Sheet; Scandinavian Ice Sheet; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; time series
ProgramEnhancing resilience in a changing climate
Released2009 08 06
AbstractThe Last Glacial Maximum (LGM) is conventionally defined as the most recent interval in Earth history when global ice sheets reached their maximum integrated volume (1) (Fig. 1). More than 30 years ago, CLIMAP used then-existing stratigraphic information to infer that the LGM occurred 18,000 14C years ago (now known to be 21,000 calendar years ago), an age that remains in wide use today (2). This singular age implies that the LGM was a transient feature in Earth history, and that ice sheets never reached an equilibrium state with the climate system. More recent reconstructions of global sea level, however, suggest that the LGM persisted for several thousand years (3-5), corresponding to an extended interval of relatively stable climate (1). Because sea level is an integrated signal, however, it does not distinguish between globally synchronous ice-sheet maxima that may have been in equilibrium throughout this interval from temporally variable regional ice-sheet maxima that combined to produce a millennia-long sea-level lowstand.
Here we use existing relative sea level (RSL) data from far-field sites to constrain the timing of the LGM as occurring from 26,000 to 19,000 years ago (26-19 ka). We then draw upon ~4200 14C ages and ~500 cosmogenic surface exposure ages (CSEAs) that span the interval from 10-50 ka to constrain the timing of maxima in global ice-sheet extent (Fig. 1). For all but the Barents-Kara Ice Sheet, the spatial distribution of ages is sufficient to evaluate regional variability in the timing of maxima for different sectors of individual ice sheets. Because ice-sheet extent scales with ice volume (6), our constraints on regional variability in ice-sheet maxima allow us to directly evaluate the temporal evolution of individual ice-sheet contributions to global sea-level change.

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