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ENSO effects on δ 18 O, δ 2 H and d‐excess values in precipitation across the U.S. using a high‐density, long‐term network (USNIP)
Author(s) -
Welker Jeffrey M.
Publication year - 2012
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6298
Subject(s) - chemistry , precipitation , term (time) , analytical chemistry (journal) , meteorology , environmental chemistry , physics , quantum mechanics
RATIONALE Isotope (δ 18 O and δ 2 H values) ratios in precipitation have been central to understanding changes in Earth's climate as recorded in ice, coral, speleothems, lake varves and long‐lived plants. Understanding how climate phases (i.e. ENSO) affect the spatial and temporal patterns of δ 18 O and δ 2 H values in precipitation has, however, been uncertain across the USA. METHODS A spatial precipitation isotope network (USNIP) has been established that aims to: (1) characterize the δ 18 O, δ 2 H and d‐excess values in precipitation across the USA with the highest spatially dense network of measurements yet undertaken; (2) quantify the annual and seasonal patterns of precipitation δ 18 O and δ 2 H values that may be affected by ENSO climate phases; and (3) provide a new isotope database for scientific studies that can be incorporated into NEON, BASIN, GNIP, and IsoMAP. RESULTS On average, precipitation δ 18 O and δ 2 H values are very low in the northern Rocky Mountain region (~ −15‰ δ 18 O, and ~ −120‰ δ 2 H), and precipitation δ 18 O and δ 2 H values are relatively higher along the Gulf Coast (~ −5‰ δ 18 O and −10‰ δ 2 H) and in the Southeast. During El Niño periods the precipitation δ 18 O and δ 2 H values are lowest in northwest Montana, with precipitation that is depleted in 18 O and 2 H extending into northern Colorado, while moisture that is enriched in 18 O and 2 H continues to dominate the Gulf Coast. The annual average differences between the climate phases generally show especially depleted 18 O and 2 H in precipitation across the Rocky Mountain region during El Niño, compared with Neutral periods. CONCLUSIONS Detailed spatial and seasonal patterns of δ 18 O, δ 2 H and d‐excess values provide fine‐scale resolution not previously recognized. Climate phases of ENSO have major effects on the spatial patterns of δ 18 O, δ 2 H and d‐excess values, being especially important on a seasonal basis in the Desert Southwest. Copyright © 2012 John Wiley & Sons, Ltd.