Browsing by Author "Houston, John"

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    High- and low-latitude forcings drive Atacama Desert rainfall variations over the past 16,000 years
    (2021) Gonzalez-Pinilla, Francisco J.; Latorre, Claudio; Rojas, Maisa; Houston, John; Ignacia Rocuant, M.; Maldonado, Antonio; Santoro, Calogero M.; Quade, Jay; Betancourt, Julio L.
    Late Quaternary precipitation dynamics in the central Andes have been linked to both high- and low-latitude atmospheric teleconnections. We use present-day relationships between fecal pellet diameters from ashy chinchilla rats (Abrocoma cinerea) and mean annual rainfall to reconstruct the timing and magnitude of pluvials (wet episodes) spanning the past 16,000 years in the Atacama Desert based on 81 C-14-dated A. cinerea paleomiddens. A transient climate simulation shows that pluvials identified at 15.9 to 14.8, 13.0 to 8.6, and 8.1 to 7.6 ka B.P. can be linked to North Atlantic (high-latitude) forcing (e. g., Heinrich Stadial 1, Younger Dryas, and Bond cold events). Holocene pluvials at 5.0 to 4.6, 3.2 to 2.1, and 1.4 to 0.7 ka B.P. are not simulated, implying low-latitude internal variability forcing (i.e., ENSO regime shifts). These results help constrain future central Andean hydroclimatic variability and hold promise for reconstructing past climates from rodent middens in desert ecosystems worldwide.
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    The role of the non-stationary Andean Dry Diagonal in paleoclimate reconstructions
    (2022) Houston, John; Latorre, Claudio
    Natural archives used to reconstruct past climates of the Atacama Desert sometimes lead to contradictory interpretations. One explanation for such contradictions is the non-stationary nature of the Andean Dry Diagonal (ADD), a narrow zone of precipitation minima between two large scale weather systems. The ADD bisects the Central Andes; to the north precipitation originates from the Atlantic Ocean via Amazonia, largely in summer, with extreme events linked to La Nina; to the south precipitation originates from the Pacific Ocean, dominated by winter storm events linked to El Nino. The dynamic nature of these weather systems implies that the position of the ADD is not stable over seasonal and longer periods. Climates currently found either north or south of the ADD may in the past have been displaced, intensified or weakened leading to changes in the position of the ADD. For example, along the coastal regions of Peru and Chile, El Nino currently modulates both winter and summer precipitation. Flood episodes caused by these precipitation events are manifested in sedimentary and other natural archives that have been used to reconstruct past climates, yet have at times, produced contradictory interpretations. The realization that ENSO has varying 'flavours' that are spatially distinct and associated with a mobile ADD may allow a more sophisticated approach to paleoclimate research that has the potential to resolve some of these difficulties.