Anthropogenic and natural contributions to the Southeast Pacific precipitation decline and recent megadrought in central Chile

Abstract

Within large uncertainties in the precipitation response to greenhouse gas forcing, the Southeast Pacific drying stands out as a robust signature within climate models. A precipitation decline, of consistent direction but of larger amplitude than obtained in simulations with historical climate forcing, has been observed in central Chile since the late 1970s. To attribute the causes of this trend, we analyze local rain gauge data and contrast them to a large ensemble of both fully coupled and sea surface temperature‐forced simulations. We show that in concomitance with large‐scale circulation changes, the Pacific Decadal Oscillation explains about half of the precipitation trend observed in central Chile. The remaining fraction is unlikely to be driven exclusively by natural phenomena but rather consistent with the simulated regional effect of anthropogenic climate change. We particularly estimate that a quarter of the rainfall deficit affecting this region since 2010 is of anthropogenic origin. An increased persistence and recurrence of droughts in central Chile emerges then as a realistic scenario under the current socioeconomic pathway.

Assessing glacier melt contribution to streamflow at Universidad Glacier, central Andes of Chile

“…Estimations of the future runoff trend and melt contribution from Universidad Glacier are beyond the scope of this work. However, the possibility of increased persistence and recurrence of droughts in central Chile (Bosier et al, 2016) would increase the hydrological importance of Universidad Glacier in the future and therefore more research is needed in order to address these issues.…”

“…Hence, glacier runoff becomes critical to maintaining flows in the Tinguiririca River during years when summer drought extends into autumn, e.g. in the period 2010-2015 (Bosier et al, 2016), and in dry winters when snowpack accumulation at highelevation sites is small. Research by Gascoin et al (2011) and Pourrier et al (2014) on glaciers of the arid Andes has revealed the hydrological importance of glaciers to the north of the Tinguiririca Basin.…”

“…The 2009/2010 hydrological year is of significance as it marks the beginning of a period of extreme aridity (2010)(2011)(2012)(2013)(2014)(2015) in central and southern Chile (Bosier et al, 2016) which extended into 2017 according to data from the Dirección General de Aguas de Chile (Chilean Water Cadastre, DGA) and Dirección Meteorológica de Chile (National Weather Service, DMC).…”

Dendrohydrology and water resources management in South-Central Chile: Lessons from the Río Imperial streamflow reconstruction

“…These proxy records can provide time series at yearly resolution, capable of delivering historical information on natural variability, estimations of return periods of extreme events such as droughts, and on the correlation with large-scale climatic forcings (Meko and Woodhouse, 2011;Sauchyn et al, 2011). In Chile, dendrohydrology has already been utilized for streamflow reconstruction in four major rivers: Maule (35 (Urrutia et al, 2011)), Biobío (37 (Muñoz et al, 2016)), Puelo (41 (Lara et al, 2008)), and Baker (47 (Lara et al, 2015)). To date, however, these studies have not yet been fully utilized for 5 watershed planning and management.…”

“…Therefore, there is need to extend the observational record to better understand longterm (e.g. centuries to millennia) variability and trends in streamflow, thus providing useful information for hydrological assessment of governmental and private planning initiatives within watersheds of SCC (Lara et al, 2015;Muñoz et al, 2016).…”