Climate-induced rhythmic oscillations in a stable glacier: Patagonia's Perito Moreno Glacier

DEPETRIS, P.J., PASQUINI, A.I.

Puerto Madryn

Congreso; XIV REUNION ARGENTINA DE SEDIMENTOLOGÍA; 2014

Asociación Argentina de Sedimentología

. In a long-term framework, most world glaciers are currently retreating, although a few appear stable or, sometimes, even advancing. Perito Moreno is a fast-flowing water-calving glacier in the Patagonian Andes, known for its stability and the concurrent rhythmic dynamics that causes the periodic ice-damming of Brazo Rico(a branch of Lake Argentino),and the ensuing collapse of the glacial terminus at the Magallanes peninsula. The system drains to the Atlantic Ocean through the Santa Cruz River. Main climatic variables appear to be coherent with ENSO; trend analysis of the 57 years-long Santa Cruz River flow series shows a significant discharge increase attributable to (austral) wintertime precipitation and springtime melt water. Here we show that the glacier?s high-frequency ice-blocking is driven by the interaction of El Niño-Southern Oscillation (ENSO) and the Antarctic Oscillation (AAO)both of which may be coupled or decoupled, with the AAO reinforcing or lessening the effect of ENSO over the southern Pacific region. The sporadic occurrence of La Niña (reinforced by a weak or positive AAO) or the absence of an El Niño event may delay or preclude damming events. Although a similar system may be active elsewhere, Moreno?s rhythm appears as a remarkable high-frequency controlling mechanism determined by specific climatic variables.