Climate controls on Andean precipitation δ 18 O interannual variability

The stable oxygen isotopic composition of precipitation (δ 18 O p ) is used as a proxy for modern and past atmospheric, biologic, and surface processes. Although the physical processes that fractionate 18 O in vapor are known, regional controls of δ 18 O p 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 δ 18 O p across four Andean domains spanning 50° latitude. Results are compared to observed δ 18 O p from meteorological stations. Simulated annual amount‐weighted mean δ 18 O p 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 δ 18 O p 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 δ 18 O p are mainly associated with precipitation amounts driven by low‐latitude sea surface temperature and Amazon Basin conditions. In the north central Andes, δ 18 O p correlates with precipitation amount and wind trajectory, which is related to the position of the Bolivian High. In the south central Andes, δ 18 O p variability is mainly influenced by precipitation amounts that are controlled by the position and strength of the westerlies. In the southern Andes, interannual δ 18 O p variability is linked to the intensification and weakening of the South Pacific High. The regional climate‐δ 18 O p relationships are discussed in the context of pre‐Quaternary sedimentary δ 18 O proxy records.