INVESTIGADORES
LECOMTE Karina Leticia
congresos y reuniones científicas
Título:
Hydroclimatic variability of Sierras Pampeanas river systems, Córdoba, Argentina: A sign of 20th century environmental change?
Autor/es:
PASQUINI, A.I.; LECOMTE, K.L.; DEPETRIS, P.J.
Lugar:
Miramar, Córdoba
Reunión:
Congreso; 3º Joint Meeting of IGCP 490 and ICSU/IUGS: Holocene environmental catastrophes in South America: From the lowlands to the Andes; 2005
Institución organizadora:
PAGES-CIGES
Resumen:
South America is subjected to the influence of various processes that impact on dominant hydrologic and climatic regimes. Noteworthy: a) the ENSO, b) the decadal signature controlled by the North Atlantic Oscillation, and c) the 15-18 year recurrence of the South American monsoon. These mechanisms are identified as relevant causes influencing anomalous rainfall and river discharge in the continent. The Sierras Pampeanas of Córdoba, Argentina, are composed of several mountain ranges with north-south orientation, cropping out between 29º 30´ and 33º 15´ S, and 63º 30´ and 65º 20´ W. The climate is semiarid with mean rainfall ranging from 500 to over 1,000 mm per year.             The Mann-Kendall trend analyses of monthly data collected in three (out of four) rainfall-gaging in the Sierras Pampeanas stations covering a record of about 55 years show a significant positive trend (p < 0.05). The seasonal Mann-Kendall test of rainfall data indicates that summer (southern hemisphere) months are responsible for this positive departure in rainfall. Moreover, studies of large rivers in the south of South America  (e.g. the Paraguay and the Paraná rivers) place the beginning of such positive trend in the early 1970s.             Rivers are rainfall integrators and mountainous catchments reflect accurately the climatic variability in areas larger than rain gages do. The discharge regime of two rivers in the region (out of six) shows significant (p < 0.05) positive Mann-Kendall trends for 60-year periods. As with rainfall, summer months show increasing trends in river discharge, although in some instances winter months (dry season) also show a significant increase.             Spectral Fourier analysis of deseasonalized discharge data (two rivers out of six) points out to two significant peaks (p < 0.001) in the period range of ~4 years and in the proximity of a decadal signal.             On the basis of the above results, we conclude that the Sierras Pampeanas of Córdoba exhibit one hydroclimatic signal that can be tied to the occurrence of ENSO events in the Pacific and another, with decadal recurrence, which seems associated with the North Atlantic Oscillation. Further, rainfall records indicate a significant increasing trend that could be interpreted as evidence of climatic change. Not all of the investigated rivers and rainfall records show, however, significant results. Hence, the existence of other factors participating in the climatic control of the region cannot be ruled out.