Climate controls on Andean precipitation delta O-18 interannual variability

• The stable oxygen isotopic composition of precipitation (O-18(p)) is used as a proxy for modern and past atmospheric, biologic, and surface processes. Although the physical processes that fractionate O-18 in vapor are known, regional controls of O-18(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 O-18(p) across four Andean domains spanning 50 degrees latitude. Results are compared to observed O-18(p) from meteorological stations. Simulated annual amount-weighted mean O-18(p) ranges between -4 and -7 (0-5 degrees S), -8 and -20 (14 degrees S-26 degrees S), -4 and -8.5 (30 degrees S-35 degrees S), and -7 to -10 (45 degrees S-50 degrees S). Relationships between climate and O-18(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 O-18(p) are mainly associated with precipitation amounts driven by low-latitude sea surface temperature and Amazon Basin conditions. In the north central Andes, O-18(p) correlates with precipitation amount and wind trajectory, which is related to the position of the Bolivian High. In the south central Andes, O-18(p) variability is mainly influenced by precipitation amounts that are controlled by the position and strength of the westerlies. In the southern Andes, interannual O-18(p) variability is linked to the intensification and weakening of the South Pacific High. The regional climate-O-18(p) relationships are discussed in the context of pre-Quaternary sedimentary O-18 proxy records.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Meteorologi och atmosfärforskning (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Meteorology and Atmospheric Sciences (hsv//eng)

Nyckelord

stable isotopes

central Andes

regional modeling

South America

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