Evidence of climate-driven changes on atmospheric, hydrological, and oceanographic variables along the Chilean coastal zone

Abstract

The Chilean coastal zone (CCZ) is subjected to a complex spectrum of anthropogenic, geophysical, biogeochemical, and climate-driven perturbations. Potentially affected variables including atmospheric sea level pressure (Pa), alongshore wind, sea surface temperature (SST), chlorophyll-a, rainfall, river discharge, relative mean sea level (RMSL), and wave climate are studied using in situ and satellite records, hindcasts, and reanalysis datasets. Linear temporal trends and correlations of anomalies are estimated between 18°S and 55°S along the CCZ. The comparison of some of the variables is achieved by means of a strict homogenization procedure on a monthly basis for 35 years. Our findings show that the poleward drift and strengthening of the Southeast Pacific Subtropical Anticyclone (SPSA) partially explains the increase in Pa and reduction in rainfall and river discharge. The enhancement of alongshore winds, also attributable to changes in the SPSA, increases coastal upwelling, which in turn could reduce SST and increase chlorophyll-a. Despite differential latitudinal responses, increasing wave heights and a southward rotation are evidenced. RMSL does not show significant variation as it is presumably affected by seafloor changes during the seismic cycle. Though some correlations are evidenced, the influence of climate variability at decadal scale (PDO, SAM) may be affecting the detected trends due to the short length of available data. Impacts on coastal communities, infrastructure, and ecosystems are discussed, aiming to highlight that coastal vulnerabilities and risk management should be based on the cumulative impacts of these variables.

River Runoff as a Major Driver of Anchovy (Engraulis ringens) Recruitment but Not of Common Sardine (Strangomera bentincki) in Central-South Chile

“…Periods of marked decrease in runoff levels could be detrimental to anchovy recruitment. Therefore, considering the current reduction of river runoff and freshwater input to the coastal zone in central-south Chile due to climate change and water use for anthropogenic activities (Garreaud et al, 2017(Garreaud et al, , 2019Grez et al, 2020), a decrease in recruitment level of anchovy is likely to occur during years of reduced runoff. Many studies have shown a relationship between freshwater input to the coastal system (through river runoff and/or precipitation) and recruitment variability of neritic fish populations (Quiñones and Montes, 2001;Lloret et al, 2004;Santojanni et al, 2006;Martín et al, 2008;Gillson, 2011;Meynecke et al, 2012).…”

“…The MegaDrought, 25% of which has been attributed to anthropogenic climate change (Boisier et al, 2016), produced a marked reduction in rainfall/runoff levels in central-south Chile. The reduction in freshwater discharge of major rivers like the Bio-Bio and Itata rivers produced a 25-75% decrease of nitrate and phosphate export to the coastal zone-nutrients which are essential for phytoplankton growth, larval development and feeding of sardine and anchovies (Grez et al, 2020). The high rainfall variability in the study area and climate model uncertainties make it difficult to predict the response of local rainfall to anthropogenic climate forcing (Boisier et al, 2016).…”

“…River runoff and precipitation in central-south Chile have a marked effect on physical, chemical and biological processes of marine ecosystems, maintaining high primary productivity rates in coastal waters (Masotti et al, 2018;Testa et al, 2018). Considering the Mega Drought (MD) that affected central-south Chile and significantly altered the spatial and temporal dynamics of runoff and precipitation levels during the 2010-2018 period (Garreaud et al, 2017(Garreaud et al, , 2019Grez et al, 2020), it is of great relevance to understand how river runoff fluctuations can influence recruitment dynamics of anchovy and common sardine, which are especially sensitive to environmental variability at all stages of their life cycle (Cubillos et al, 2007b;Yáñez et al, 2008;Gomez et al, 2012). The hypothesis of this study was formulated based on the premise that changes in freshwater input to the coastal zone at different time/spatial scales may be contributing to the triggering of marked changes in anchovy and common sardine population dynamics in central-south Chile.…”

Integrated Analysis of the Combined Risk of Ground Subsidence, Sea Level Rise, and Natural Hazards in Coastal and Delta River Regions

“…Additionally, local relative SLR can be significantly modulated in coastal regions by vertical ground motions (i.e., subsidence phenomena) either due to natural processes (e.g., global isostatic adjustment, tectonics, sediment consolidation and compaction, and upstream sediment load reduction) [4][5][6][7] or induced/influenced by human activities (e.g., groundwater extraction [8], land reclamation [9], building construction, and consolidation [10]). Ground deformations can be on the same order of magnitude (or greater) than climate-induced SLR [11]. However, in practice, coastal ground motions are often poorly known, and little information is practically available in many cases about the spatial and temporal evolution of ground motion.…”

“…Figure11. The tidal anomaly correlation computed from the combination of the four largest tidal constituent amplitudes (given by the detrended sum of the M2 + S2 + K1 + O1) as a proxy for the change in the approximate highest astronomical tide (δ-HAT) relative to detrended MSL in Hong Kong, with the marker size showing the relative magnitude according to the legend, in units of mm m-1.…”