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

Glaciar Jorge Montt (48 20 0 S/73 30 0 W), one of the main tidewater glaciers of the Southern Patagonian Ice- field (SPI), has experienced the greatest terminal retreat ob- served in Patagonia during the past century, with a reces- sion of 19.5 km between 1898 and 2011. This retreat has re- vealed 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 Lit- tle 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 re- treat 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 dy- namic 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 ve- locities.

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