New paper shows major glacier was smaller than the present during the Medieval Warming Period

A paper published today in the journal Climate of the Past used radiocarbon dating to determine the age of trees uncovered in 2003 by retreat of a major glacier located in Southern Patagonia. The authors conclude that the glacier was smaller than the present during the Medieval Warming Period, and that the trees were covered by advance of the glacier during the Little Ice Age from 460 to 250 years ago.

Clim. Past, 8, 403-414, 2012
www.clim-past.net/8/403/2012/
doi:10.5194/cp-8-403-2012


Little Ice Age advance and retreat of Glaciar Jorge Montt, Chilean Patagonia

A. Rivera^1,2, M. Koppes³, C. Bravo¹, and J. C. Aravena^4
1Centro de Estudios Científicos (CECS), Valdivia, Chile
²Departamento de Geografía, Universidad de Chile, Santiago, Chile
³Department of Geography, University of British Columbia, Vancouver, Canada
⁴Centro de Estudios del Cuaternario Fuego-Patagonia y Antártica (Fundación CEQUA) Conicyt Regional R07C1002., Punta Arenas, Chile


Abstract. Glaciar Jorge Montt (48°20' S/73°30' W), one of the main tidewater glaciers of the Southern Patagonian Icefield (SPI), has experienced the greatest terminal retreat observed in Patagonia during the past century, with a recession of 19.5 km between 1898 and 2011. This retreat has revealed trees laying subglacially until 2003. These trees were dated using radiocarbon, yielding burial ages between 460 and 250 cal yrs BP. The presence of old growth forest during those dates indicates that Glaciar Jorge Montt was upvalley of its present position before the commonly recognized Little Ice Age (LIA) period in Patagonia. The post-LIA retreat was most likely triggered by climatically induced changes during the 20th century; however, Glaciar Jorge Montt has responded more dramatically than its neighbours. The retreat of Jorge Montt opened a 19.5 km long fjord since 1898, which reaches depths in excess of 390 m. The bathymetry is well correlated with glacier retreat rates, suggesting that dynamic responses of the glacier are at least partially connected to near buoyancy conditions at the ice front, resulting in high calving fluxes, accelerating thinning rates and rapid ice velocities.

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