Browsing by Author "Rojas, Maisa"

Now showing 1 - 6 of 6
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    An improved land biosphere module for use in reduced complexity Earth System Models with application to the last glacial
    (2017) Eichinger, Roland; Shaffer, Gary; Albarran, Nelson; Rojas, Maisa; Lambert, Fabrice
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    An improved land biosphere module for use in the DCESS Earth system model (version 1.1) with application to the last glacial termination
    (2017) Eichinger, Roland; Shaffer, Gary; Albarran, Nelson; Rojas, Maisa; Lambert, Fabrice
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    Diversifying Chile's climate action away from industrial plantations
    (2021) Hoyos-Santillan, Jorge; Miranda, Alejandro; Lara, Antonio; Sepulveda-Jauregui, Armando; Zamorano-Elgueta, Carlos; Gomez-Gonzalez, Susana; Vasquez-Lavin, Felipe; Garreaud, Rene D.; Rojas, Maisa
    As president of the Climate Change Conference of the Parties, Chile has advocated for developing ambitious commitments to mitigate greenhouse gas emissions to achieve carbon-neutrality by 2050. However, Chile's motivations and ambitious push to reach carbon-neutrality are complicated by a backdrop of severe drought, climate change impacts (i.e., wildfires, tree mortality), and the use of industrial plantations as a mitigation strategy. This has become more evident as widespread and severe wildfires have impacted large areas of industrial plantations, transforming the land-use, land-use change, and forestry sector from a carbon sink to a net carbon source. Consequently, Chile must diversify its climate actions to achieve carbon-neutrality. Nature-based solutions, including wetlands-peatlands and oceans, represent alternative climate actions that can be implemented to tackle greenhouse gas emissions at a national level. Diversification, however, must guarantee Chile's long-term carbon sequestration capacity without compromising the ecological functionality of biodiverse treeless habitats and native forest ecosystems.
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    Emergence of robust precipitation changes across crop production areas in the 21st century
    (2019) Rojas, Maisa; Lambert, Fabrice; Ramírez Villegas, Juián; Challinor, Andrew J,
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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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    Radiocarbon bomb-peak signal in tree-rings from the tropical Andes register low latitude atmospheric dynamics in the Southern Hemisphere
    (2021) Ancapichun, Santiago; De Pol-Holz, Ricardo; Christie, Duncan A.; Santos, Guaciara M.; Collado-Fabbri, Silvana; Garreaud, Rene; Lambert, Fabrice; Orfanoz-Cheuquelaf, Andrea; Rojas, Maisa; Southon, John; Turnbull, Jocelyn C.; Creasman, Pearce Paul
    South American tropical climate is strongly related to the tropical low-pressure belt associated with the South American monsoon system. Despite its central societal role as a modulating agent of rainfall in tropical South America, its long-term dynamical variability is still poorly understood. Here we combine a new (and world's highest) tree-ring C-14 record from the Altiplano plateau in the central Andes with other C-14 records from the Southern Hemisphere during the second half of the 20th century in order to elucidate the latitudinal gradients associated with the dissemination of the bomb C-14 signal. Our tree-ring C-14 record faithfully captured the bomb signal of the 1960's with an excellent match to atmospheric C-14 measured in NewZealand but with significant differences with a recent record from Southeast Brazil located at almost equal latitude. These results imply that the spreading of the bomb signal throughout the Southern Hemisphere was a complex process that depended on atmospheric dynamics and surface topography generating reversals on the expected north-south gradient in certain years. We applied air-parcelmodeling based on climate data to disentangle their different geographical provenances and their preformed (reservoir affected) radiocarbon content. We found that air parcel trajectories arriving at the Altiplano during the bomb period were sourced i) from the boundary layer in contact with the Pacific Ocean (41%), ii) fromthe upper troposphere (air above the boundary layer, with no contact with oceanic or continental carbon reservoirs) (38%) and iii) fromthe Amazon basin (21%). Based on these results we estimated the Delta C-14 endmember values for the different carbon reservoirs affecting our recordwhich suggest that the Amazon basin biospheric C-14 isoflux could have been reversed fromnegative to positive as early as the beginning of the 1970's. Thiswould imply amuch faster carbon turnover rate in the Amazon than previouslymodelled. (c) 2021 Elsevier B.V. All rights reserved.