Abstract
Abstract. The South Pacific Subtropical High (SPSH) is a predominant feature of the South American climate. The variability of this high-pressure center induces changes in the intensity of coastal alongshore winds and precipitation, among others, over southwestern South America. In recent decades, strengthening and expansion of the SPSH have been observed and attributed to the current global warming. These changes have led to an intensification of the southerly winds along the coast of northern to central Chile and a decrease in precipitation from central to southern Chile. Motivated by improving our understanding about the regional impacts of climate change in this part of the Southern Hemisphere, we analyzed SPSH changes during the two most extreme climate events of the last millennium, the Little Ice Age (LIA) and the Current Warm Period (CWP: 1970–2000), based on paleoclimate records and CMIP5/PMIP3 model simulations. In order to assess the level of agreement of general circulation models, we also compare them with ERA-Interim reanalysis data for the 1979–2009 period as a complementary analysis. Finally, with the aim of evaluating future SPSH behavior, we include 21st century projections under a Representative Concentration Pathway (RCP8.5) scenario in our analyses. Our results indicate that during the relative warm (cold) period, the SPSH expands (contracts). Together with this change, alongshore winds intensify (weaken) south (north) of ∼35∘ S; also, southern westerly winds become stronger (weaker) and shift southward (northward). Model results generally underestimate reanalysis data. These changes are in good agreement with paleoclimate records, which suggest that these variations could be related to tropical climate dynamics but also to extratropical phenomena. However, although models adequately represent most of the South American climate changes, they fail to represent the Intertropical Convergence Zone–Hadley cell system dynamics, emphasizing the importance of improving tropical system dynamics in simulations for a better understanding of its effects on South America. Climate model projections indicate that changes recently observed will continue during the next decades, highlighting the need to establish effective mitigation and adaptation strategies against their environmental and socioeconomic impacts.
Highlights
Climate conditions in South America (SA) are the result of the complex interactions among predominant atmospheric circulation patterns, orographic features, latitudinal differential radiation, and heat and water balances
Several paleoclimate records analyzed (Table 3, Fig. 2) indicate that important changes have occurred during the late Holocene along the western margin of South America
Our results suggest important relative changes in major climatic features of the western margin of South America during the late Holocene
Summary
Climate conditions in South America (SA) are the result of the complex interactions among predominant atmospheric circulation patterns, orographic features, latitudinal differential radiation, and heat and water balances. An intensification of coastal southerly winds and a decrease in precipitation have been observed in southwestern SA. These changes have been related to an intensified and southward-shifted SPSH as a response to the current global warming scenario (Falvey and Garreaud, 2009; Rahn and Garreaud, 2013; Ancapichún and Garcés-Vargas, 2015; Schneider et al, 2017; Boisier et al, 2018; Aguirre et al, 2018). Model projections indicate that this trend will continue during the 21st century for southerly wind intensity (e.g., Garreaud and Falvey, 2009; Belmadani et al, 2014; Aguirre et al, 2018), as well as for precipitation (e.g., Nuñez et al, 2008; Kitoh et al, 2011; Cabré et al, 2016)
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