Interannual-to-multidecadal hydroclimate variability and its sectoral impacts in northeastern Argentina

Abstract

Abstract. This study examines the joint variability of precipitation, river streamflow and temperature over northeastern Argentina; advances the understanding of their links with global SST forcing; and discusses their impacts on water resources, agriculture and human settlements. The leading patterns of variability, and their nonlinear trends and cycles are identified by means of a principal component analysis (PCA) complemented with a singular spectrum analysis (SSA). Interannual hydroclimatic variability centers on two broad frequency bands: one of 2.5–6.5 years corresponding to El Niño Southern Oscillation (ENSO) periodicities and the second of about 9 years. The higher frequencies of the precipitation variability (2.5–4 years) favored extreme events after 2000, even during moderate extreme phases of the ENSO. Minimum temperature is correlated with ENSO with a main frequency close to 3 years. Maximum temperature time series correlate well with SST variability over the South Atlantic, Indian and Pacific oceans with a 9-year frequency. Interdecadal variability is characterized by low-frequency trends and multidecadal oscillations that have induced a transition from dryer and cooler climate to wetter and warmer decades starting in the mid-twentieth century. The Paraná River streamflow is influenced by North and South Atlantic SSTs with bidecadal periodicities. The hydroclimate variability at all timescales had significant sectoral impacts. Frequent wet events between 1970 and 2005 favored floods that affected agricultural and livestock productivity and forced population displacements. On the other hand, agricultural droughts resulted in soil moisture deficits that affected crops at critical growth stages. Hydrological droughts affected surface water resources, causing water and food scarcity and stressing the capacity for hydropower generation. Lastly, increases in minimum temperature reduced wheat and barley yields.

Interannual and Long-Term Precipitation Variability Along the Subtropical Mountains and Adjacent Chaco (22–29° S) in Argentina

“…This extended record captures the main features in rainfall variability including the increase in precipitation in the 1970s that lasts for almost four decades to 2008, as registered not only by the interannual amplitudes, but also by the Rodionov shift test. This extended record is in agreement with multi-decadal precipitation variations derived by Lovino et al (2018) from the GPCP gridded dataset for the nearby northeastern Argentina region. According to these authors, the first PC, which ranges from 1905 to 2010 and accounts for 60% of the total variance, shows a persistent wet period between 1970 and 2005, followed by a dry period thenceforth.…”

“…The increase in precipitation over NWA (22 • -29 • S and 62.5 • -67 • W) since 1970s identified in the 34 records (Supplementary Material) compiled in this study, from the Chaco lowlands through the Andean mountain range, to high-elevation Prepuna, suggesting that this change in mean conditions respond to large-scales climate variability. Castino et al (2017) results reflect similar patterns in NWA, while Lovino et al (2018) show analogous variations in the nearby region of northeastern Argentina. According to our records, the positive trend in precipitation has leveled during the last years (from 2010s).…”

“…According to our records, the positive trend in precipitation has leveled during the last years (from 2010s). The interruption in the positive trend has also been identified in surrounding regions including the central-western Argentina (29 • -36 • S; Agosta and Compagnucci, 2012) and northeastern Argentina (Lovino et al, 2018). The recent changes in precipitation trends have been attributed by these authors to Pacific low-frequency SST variability.…”

Observed and Projected Changes in Temperature and Precipitation in the Core Crop Region of the Humid Pampa, Argentina

“…The large inter-annual variability observed in Figure 4, including water deficits and excesses, is characteristic of the central-northeastern region of Argentina and has cycles of 2-6 and 9 years [7]. As shown by Lovino et al ( [10] and references therein), most excesses were related to EN years, while deficits were related to LN years.…”

“…Consistently, southeastern South America (SSA) tends towards warmer and moister conditions, with a noticeable increase in the magnitude and frequency of extreme temperatures and heavy rainfall (e.g., [4,5]). In particular, centralnortheastern Argentina has been experiencing these significant climate changes since the 1960s [6,7]. The continuous increase in frequency and in intensity of heavy rainfall has caused great losses in agro-industrial production, severely damaged water management, and affected the urban centers in the region [8,9].…”