Recent lake level variability in Andean Patagonian, Argentina.

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

GLOBAL AND PLANETARY CHANGE

Elsevier

Año: 2008 vol. 63 p. 290 - 298

0921-8181

Abstract: A long series of lakes (~150) borders the Patagonian Andes (south of ~38ºS), most of which are a geomorphologic relict of Pleistocene glaciations. Employing instrumental records, we inspected lake water level departures from seasonal variations in seven proglacial lakes: Lacar, Mascardi, Steffen, Escondido, Puelo, Vinter, and Argentino. Lakes north of ~42ºS show maximum gage (water) level during (austral) winter months; lakes between ~42º and ~45ºS appear as transitional; the lake south of ~50ºS (Argentino) shows maximum water level in early autumn. Most lakes show moderate level fluctuation throughout yearly records and, in general, show heteroscedacity. Furthermore, Hurst exponents reveal a persistent (i.e., long-term memory effect) behavior in all water level series. In most lakes there are no trends in desesasonalized mean and maximum water levels (Seasonal Kendall test). Lake Mascardi-Manso River system (mostly fed by melt water from the retreating Manso Glacier) is a contrasting example that shows a decreasing trend during summer months that we ascribe to the also declining ice volume. The harmonic analysis (Fourier and wavelet transform) of desesasonalized mean and maximum water level time series shows interannual and decadal periodicities that we link to the occurrence of El Niñ and/or the Antarctic Oscillation. The associated phase spectrum indicates that there is ~13-month lag between ENSO occurrences and its effect on anomalous lake water levels. Increased snow accumulation during (austral) winters usually follows the (austral) summertime El Niñ events, which normally result in increased melt water volume that occurs with about one-year delay during the following (austral) spring/summer.