Patagonian Ice Sheet
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The Patagonian Ice Sheet was a large elongated and narrow ice sheet that covered all of Chile south of approximately present-day Puerto Montt during the Last Glacial Maximum. Some maps have the Patagonian Ice Sheet connected to the icecaps of the Altiplano by continuous glaciers all the way through the Andes.
The ice sheet extended beyond the crest of the Andes into Argentina, but because of the dryness of the climate it did not reach beyond present-day lakes such as the Yagagtoo, Musters, and Colhue Huapi. At its peak (about 18,000-17,500 years ago1), the Patagonian Ice Sheet covered about 480,000 km² of land with an estimated ice-volume of more than 500,000 km³ (1), of which about 4 % remains glaciated today in two separated portions known as the Northern and Southern Patagonian Ice Fields. The ice-volume reduction contributed to the global sea-level rise with about 1.2 meters(1). However, during the first glacial period at the beginning of the Pleistocene ice extended to the present-day Argentine coast. With each successive glaciation it is known that the ice has stopped further and further to the west, with aridity always serving as the decisive factor halting glacier spread: it is believed that the east-west precipitation gradients during glacial periods were even steeper than the extremely steep ones of present-day Patagonia.
Unlike the Laurentide Ice Sheet or the ice sheets of Northern Europe, the Patagonian Ice Sheet did not cause major extinctions or loss of biodiversity. This is because the flora remaining to the north of the ice was isolated by the Atacama Desert and was able to speciate easily wherever suitable microclimates occurred. In fact, most of the original Antarctic flora survives today on land occupied by the ice sheet. However, there are indications that during the last deglaciation (17,500 years ago), the rapid melting of the northern most extension of the Patagonian Ice Sheet resulted in a dramatic release of fresh-water to the adjacent ocean, decreasing its salinity (2) and altering its circulation (3), resulting in significant ecological changes both locally and remotely (3).
[edit] References
(1) Hulton, N.R.J., R.S. Purvesa, R.D. McCullocha, D.E. Sugdena, M.J. Bentleyb. 2002. The Last Glacial Maximum and eglaciation in southern South America. Quaternary Science Reviews , vol. 21, 233–241.
(2) Lamy, F., J. Kaiser, U. Ninnemann, D. Hebbeln, H. W. Arz, J. Stoner. 2004. Antarctic Timing of Surface Water Changes off Chile and Patagonian Ice Sheet Response. Science, vol. 304, 1959-1962.
(3) De Pol-Holz, R., O. Ulloa, L. Dezileau, J. Kaiser, F. Lamy and D. Hebbeln. 2006. Melting of the Patagonian Ice Sheet and deglacial perturbations of the nitrogen cycle in the eastern South Pacific. Geophysical Research Letters, vol. 33, L04704, doi:10.1029/2005GL024477.
