Recent lake level variability in Patagonia, Argentina

PASQUINI, A.I.; LECOMTE, K.L.; DEPETRIS, P.J.

Malargïe, Mendoza

Simposio; Simposio sobre: Variaciones Climáticas en América del Sur durante el Holoceno tardío.; 2006

PAGES-IANIGLIA

As a geomorphologic relict of Pleistocene glaciations, a string of numerous proglacial lakes borders the Patagonian Andes (South of ~38ºS). We have inspected the anomalous departures from seasonal variations in instrumental records (at most ~45 years-long) collected in several lakes: Lacar, Mascardi, Steffen, Escondido, Puelo, Vinter, Argentino, and Rico. Lakes north of 41ºS show maximum gage (water) level during (southern) winter months; lakes between ~42ºS and ~45ºS appear as transitional; lakes south of ~50ºS show maximum gage level in early fall. Most lakes show a pronounced level fluctuation throughout the available yearly records and, in general, violate homoscedacity. Lake Argentino shows narrow water level variability (5-9%), and most vary between 20 and 30%. Seasonal Kendall test shows that, in general, there are no trends in anomalous lake water levels (i.e., desesasonalized). Lake Mascardi (mostly fed by meltwater from the retreating Tronador Glacier) is a contrasting example, showing a decreasing trend in level anomalies during summer months. Likewise, the Manso River (both, feeding and draining the Mascardi) shows a decreasing trend in historical discharge anomalies.  The harmonic analysis of anomalous lake levels shows interannual and decadal periodicities in lakes Mascardi, Escondido, Lacar, and Argentino. In addition, a quasi-decadal oscillation was also observed in lakes Steffen, Puelo, and Vinter. There are indications that there is a significant coherence between water level anomalies among lakes and also with ENSO occurrences in the Pacific. The associated phase spectra indicate that there are 12-15 months lags between ENSO occurrences and its effect on anomalous lake water levels.