The neoglaciation ("renewed
glaciation") describes the documented cooling trend in the
Earth's climate during the
Holocene, following the retreat of the
Wisconsin glaciation, the
most recent glacial period. Neoglaciation has followed the hypsithermal or
Holocene Climatic Optimum, the warmest point in the Earth's climate during the current
interglacial stage, excluding the
global warming-induced temperature increase starting in the 20th century. The neoglaciation has no well-marked universal beginning: local conditions and
ecological inertia affected the onset of detectably cooler (and wetter) conditions.
Driven inexorably by the
Milankovitch cycle, cooler summers in higher latitudes of North America, which would cease to completely melt the annual snowfall, were masked at first by the presence of the slowly disappearing continental ice sheets, which persisted long after the astronomically calculated
moment of maximum summer warmth: "the neoglaciation can be said to have begun when the cooling caught up with the warming", remarked
E. C. Pielou.[1] With the close of the "
Little Ice Age" (mid-14th to late 19th centuries), neoglaciation appears to have been reversed in the late 20th century, evidently caused by
anthropogenicglobal warming. Neoglaciation had been marked by a retreat from the warm conditions of the
Climatic Optimum and the advance or reformation of
glaciers that had not existed since the last
ice age. In the mountains of western North America, montane glaciers that had completely melted reformed shortly before 5000
BP.[2] The most severe part of the best documented neoglacial period, especially in Europe and the North Atlantic, is termed the "
Little Ice Age".
In North America, neoglaciation had ecological effects in the spread of
muskeg on flat, poorly drained land, such as the bed of recently drained
Lake Agassiz and in the
Hudson Bay lowlands, in the retreat of grassland before an advancing forest border in the
Great Plains, and in shifting ranges of forest trees and
diagnostic plant species (identified through
palynology).
^E.C. Pielou 1991:291; S.C. Porter and G.H. Denton, "Chronology of the neo-glaciation in the North American cordillera", American Journal of Science265 (1967:177-210), noted in E.C. Pielou, After the Ice Age: The Return of Life to Glaciated North America (Chicago: University of Chicago Press) 1991:15 note 13. Pielou discusses the neoglaciation in ch. 14 "The Neoglaciation" pp 291-310.
^Pielou 1991:291;
geomorphology of
glacial moraines suggest that mountain glaciers in
British Columbia have advanced and receded twice more recently, with advances peaking about 2800 BP and 300 BP (noting G.H. Denton and W. Karlen, ""Holocene climatic variations— their pattern and possible cause", Quaternary Research3 1973:155-205), and J.M. Ryder and B. Thomson, "Neoglaciation in the southern Coast Mountains of British Columbia: chronology prior to the Late Neoglacial Maximum", Canadian Journal of Earth Sciences23 1986:273-87.
^Gavin, Daniel G.; Henderson, Andrew C.G.; Westover, Karlyn S.;
Fritz, Sherilyn C.; Walker, Ian R.; Leng, Melanie J.; Hu, Feng Sheng (2011). "Abrupt Holocene climate change and potential response to solar forcing in western Canada". Quaternary Science Reviews. 30 (9–10): 1243–1255.
Bibcode:
2011QSRv...30.1243G.
doi:
10.1016/j.quascirev.2011.03.003.
^Menounos, Brian; Osborn, Gerald; Clague, John J.; Luckman, Brian H. (2009). "Latest Pleistocene and Holocene glacier fluctuations in western Canada". Quaternary Science Reviews. 28 (21–22): 2049–2074.
Bibcode:
2009QSRv...28.2049M.
doi:
10.1016/j.quascirev.2008.10.018.
^Osborn, Gerald; Menounos, Brian; Ryane, Chanone; Riedel, Jon; Clague, John J.; Koch, Johannes; Clark, Douglas; Scott, Kevin; Davis, P. Thompson (2012). "Latest Pleistocene and Holocene glacier fluctuations on Mount Baker, Washington". Quaternary Science Reviews. 49: 33–51.
Bibcode:
2012QSRv...49...33O.
doi:
10.1016/j.quascirev.2012.06.004.