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The stable oxygen isotopic composition of precipitation (δ18Op) is used as a proxy for modern and past atmospheric, biologic, and surface processes. Although the physical processes that fractionate 18O in vapor are known, regional controls of δ18Op are not well understood. Here we present results from a limited‐domain general circulation model (REMOiso) to quantify regional controls on modern (1976–1999) interannual and spatial variations of δ18Op across four Andean domains spanning 50° latitude. Results are compared to observed δ18Op from meteorological stations. Simulated annual amount‐weighted mean δ18Op ranges between −4 and −7‰ (0–5°S), −8 and −20‰ (14°S–26°S), −4 and −8.5‰ (30°S–35°S), and −7 to −10‰ (45°S–50°S). Relationships between climate and δ18Op on interannual timescale vary along the Andes and are tied to changes in precipitation and large‐scale dynamics. In the northern Andes, interannual variations in δ18Op are mainly associated with precipitation amounts driven by low‐latitude sea surface temperature and Amazon Basin conditions. In the north central Andes, δ18Op correlates with precipitation amount and wind trajectory, which is related to the position of the Bolivian High. In the south central Andes, δ18Op variability is mainly influenced by precipitation amounts that are controlled by the position and strength of the westerlies. In the southern Andes, interannual δ18Op variability is linked to the intensification and weakening of the South Pacific High. The regional climate‐δ18Op relationships are discussed in the context of pre‐Quaternary sedimentary δ18O proxy records.

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Constraining the pre‐Neogene history of the Puna plateau is crucial for establishing the initial conditions that attended the early stage evolution of the southern extent of the Andean plateau. We apply high‐ to low‐temperature thermochronology data from plutonic rocks in northwestern Argentina to quantify the Paleozoic, Mesozoic and early Tertiary cooling history of the Andean crust. U‐Pb crystallization ages of zircons indicate that pluton intrusion occurred during the early mid‐Ordovician (490–470 Ma) and the late Jurassic (160–150 Ma). Lower‐temperature cooling histories from40Ar/39Ar analyses of K‐feldspar vary substantially. Basement rocks underlying the western Puna resided at temperatures below 200°C (<6 km depth) since the Devonian (∼400 Ma). In contrast, basement rocks underlying the southeastern Puna were hotter (∼200–300°C) throughout the Paleozoic and Jurassic and cooled to temperatures of <200°C by ∼120 Ma. The southeastern Puna basement records a rapid cooling phase coeval with active extension of the Cretaceous Salta rift at ∼160–100 Ma that we associate with tectonic faulting and lithospheric thinning. The northeastern Puna experienced protracted cooling until the late Cretaceous with temperatures <200°C during the Paleocene. Higher cooling rates between 78 and 55 Ma are associated with thermal subsidence during the postrift stage of the Salta rift and/or shortening‐related flexural subsidence. Accelerated cooling and deformation during the Eocene was focused within a narrow zone along the eastern Puna/Eastern Cordillera transition that coincides with Paleozoic/Mesozoic structural and thermal boundaries. Our results constrain regional erosion‐induced cooling throughout the Cenozoic to have been less than ∼150°C, which implies total Cenozoic denudation of <6–4 km.

The response of summer precipitation in the western United States to climate variability remains a subject of uncertainty. For example, palaeoclimate records indicate the North American Monsoon (NAM) was stronger and spatially more extensive during the Holocene, whereas recent modelling suggests a weakened NAM response to increasing temperatures. These illustrate diverging pictures of the NAM response to warming. Here, we examine summer precipitation in the southwestern US related to Last Interglacial insolation forcing. Using a high-resolution climate model, we find that Eemian insolation forcing results in overall wetter conditions throughout most of the southwestern US, but significantly drier than present conditions over Arizona. The overall wetter conditions are associated with a northward shift of the anticyclonic circulation aloft and increased moisture in the lower and mid-troposphere during the Eemian. Increased advection of Gulf of Mexico moisture is responsible for increasing precipitation in New Mexico and the northern edges of the NAM region. Drier conditions over Arizona are likely related to reduced local convection associated with reduced vertical moisture transport. These results highlight the spatial complexity of the NAM response to increasing radiative forcing and allow a better understanding of monsoon dynamics and variability in response to a warming climate.