Dominant ENSO frequencies during the Little Ice Age in Northern Patagonia: The varved record of proglacial Lago Frías, Argentina

The global character of the time interval known as the Little Ice Age (LIA) is at present relatively well established. However, the forcing mechanisms behind this cooling interval are still elusive. Investigations in annually laminated sediments have shown that varved sediments are among the best climate archives to tackle these questions. Proglacial Lago Frías in northern Patagonia is fed by the Tronador ice cap (3554 m). Previous investigations have shown that this glacier has reacted sensitively to climate change during the LIA, with well-identified major glacial advances between AD 1800–1850. Results of a multiproxy study of Lago Frías sediments reflect variations in the transport of glacially derived clay and silt to the basin that can be directly linked to changes in climate. Sedimentological evidence combined with a chronological model indicate variations in varve thicknesses showing two frequencies centered at 16.4 and 10.5 years that have been previously attributed to the solar cycles and the Tropical Atlantic Sea Surface Dipole (TAD), respectively. The main frequency is, however, located between 2.5 and 3.0 years pointing towards a dominant El Niño/Southern Oscillation (ENSO) signal. Thus, the Lago Frías record provides new insights about the complexity of the various forcing mechanisms behind the cooling during the LIA in an area with a paucity of high-resolution climate records.