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South American (SA) societies are highly vulnerable to droughts and pluvials, but lack of long-term climate observations severely limits our understanding of the global processes driving climatic variability in the region. The number and quality of SA climate-sensitive tree ring chronologies have significantly increased in recent decades, now providing a robust network of 286 records for characterizing hydroclimate variability since 1400 CE. We combine this network with a self-calibrated Palmer Drought Severity Index (scPDSI) dataset to derive the South American Drought Atlas (SADA) over the continent south of 12°S. The gridded annual reconstruction of austral summer scPDSI is the most spatially complete estimate of SA hydroclimate to date, and well matches past historical dry/wet events. Relating the SADA to the Australia–New Zealand Drought Atlas, sea surface temperatures and atmospheric pressure fields, we determine that the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) are strongly associated with spatially extended droughts and pluvials over the SADA domain during the past several centuries. SADA also exhibits more extended severe droughts and extreme pluvials since the mid-20th century. Extensive droughts are consistent with the observed 20th-century trend toward positive SAM anomalies concomitant with the weakening of midlatitude Westerlies, while low-level moisture transport intensified by global warming has favored extreme rainfall across the subtropics. The SADA thus provides a long-term context for observed hydroclimatic changes and for 21st-century Intergovernmental Panel on Climate Change (IPCC) projections that suggest SA will experience more frequent/severe droughts and rainfall events as a consequence of increasing greenhouse gas emissions.
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Geotechnical Engineering in the Face of Climate Change: Role of Multi-Physics Processes in Partially Saturated Soils
Climate change is expected to alter the statistics of extreme events including rainfall storms, floods, droughts, and heatwaves. Climate-adaptive geotechnical structures warrant a quantitative assessment of the impacts of emerging and projected extreme patterns on the short and long-term behaviors of earthen structures. Furthermore, long-term changes to soil carbon and moisture due to non-extreme climate events should also be considered. While several large-scale studies have been conducted to evaluate various aspects of climate change, there is a clear gap in the state of knowledge in terms of assessing the resilience of geotechnical structures to changes in climatic trends (e.g., warmer climate, protracted droughts, intensified extreme precipitations, and sea level rise). The majority of the aforementioned climatic trends pose multi-physics problems involving thermo-hydro-mechanical (THM) processes in partially saturated soils and earthen structures. This review paper discusses how soil-atmospheric interactions and extreme event patterns in a changing climate can alter soil properties and loading conditions, affecting the performance of partially saturated geotechnical structures. We speculate how changes in climatic trends may weaken partially saturated earthen structures through strength reduction, drying, soil desiccation cracking, shrinkage, microbial oxidation of soil organic matter, fluctuation in the ground water table, land and surface erosion, and highly dynamic pore pressure changes. Each of these weakening processes is primarily induced by variations in the soil moisture and temperature. Finally, we discuss potential modes of failure imposed on partially saturated earthen structures by climatic trends.
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- PAR ID:
- 10065749
- Date Published:
- Journal Name:
- Proc. 2018 International Foundations Congress and Equipment Exposition, IFCEE 2018: Advances in Geomaterial Modeling and Site Characterization, Geotechnical Special Publication No. 295
- Page Range / eLocation ID:
- 353 to 364
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1061/9780784481585.035
