River‐discharge dynamics in the Southern Central Andes and the 1976–77 global climate shift

Abstract

Recent studies have shown that the 1976–77 global climate shift strongly affected the South American climate. In our study, we observed a link between this climate shift and river‐discharge variability in the subtropical Southern Central Andes. We analyzed the daily river‐discharge time series between 1940 and 1999 from small to medium mountain drainage basins (102–104 km2) across a steep climatic and topographic gradient. We document that the discharge frequency distribution changed significantly, with higher percentiles exhibiting more pronounced trends. A change point between 1971 and 1977 marked an intensification of the hydrological cycle, which resulted in increased river discharge. In the upper Rio Bermejo basin of the northernmost Argentine Andes, the mean annual discharge increased by 40% over 7 years. Our findings are important for flood risk management in areas impacted by the 1976–77 climate shift; discharge frequency distribution analysis provides important insights into the variability of the hydrological cycle in the Andean realm.

Applications of SAR Interferometric Coherence Time Series: Spatiotemporal Dynamics of Geomorphic Transitions in the South‐Central Andes

“…The semiarid to arid conditions of the Quebrada del Toro and Pocitos basins result in generally high SAR coherence values (Figures a and c). During the wet season, rainstorms penetrate into the Quebrada del Toro (mean annual rainfall ~1 m/year) and more rarely into the Pocitos region (~0.2 m/year), resulting in most of the sediment transport occurring during this time period (Castino et al, ). Low coherence values, correspondingly, are focused during the wet season (Figures b and d).…”

“…The Quebrada del Toro in particular serves as a representative example of the climatic and topographic gradients found throughout the south‐central Andes (e.g., Bookhagen & Strecker, , ; Castino et al, , ; Purinton & Bookhagen, ; Tofelde et al, , ). The lower Quebrada del Toro is typified by a steep gorge with relatively high precipitation, moderate vegetation, and a steep hillslope gradient (Figure ).…”

“…As moisture impinges on the eastern flanks of the orogen, a pronounced orographic rainfall effect is generated (Bookhagen & Strecker, 2008;Castino et al, 2016). This strong E-W climatic gradient across the south-central Andes is superposed by a weaker and more gradual along-strike (N-S) rainfall gradient from the central to south-central Andes along the eastern Andean front (Boers et al, 2015;Castino et al, 2016;Vera et al, 2006). The climate systems that deliver precipitation into the south-central Andes are highly seasonal, with wet austral summers (NDJFMA) and dry austral winters (MJJASO).…”

Measuring Decadal Vertical Land-level Changes from SRTM-C (2000) and TanDEM-X (~ 2015) in the South-Central Andes

“…1) to identify and measure areas of dh in gravel-bed channels specifically and then across the landscape. Here, steep gradients in elevation (~1-4 km), rainfall (~0.1-1 m/yr), and vegetation (sub-tropical forests and croplands to arid, succulent-covered slopes) cause high rates of mass transfer (Bookhagen and Strecker, 2012;Savi et al, 2016;Schildgen et al, 2016), further influenced by climate change (Castino et al, 2016a(Castino et al, , b, 2017 and anthropogenic modification (gravel mining and weirs). To conclude, we discuss caveats driven by remaining uncertainties prevalent in spaceborne DEMs collected over complex topography.…”

“…Locally, the aggrading and incising patches may be related to braided channel avulsion and subsequent rapid incision into the unconsolidated bed material during frequent high-discharge events brought by convective rainfall in the summer monsoon (Castino et al, 2016a(Castino et al, , b, 2017. In map-view (Fig.…”