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Triple water‐isotopologue record from WAIS Divide, Antarctica: Controls on glacial‐interglacial changes in 17 O excess of precipitation
Author(s) -
Schoenemann Spruce W.,
Steig Eric J.,
Ding Qinghua,
Markle Bradley R.,
Schauer Andrew J.
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2014jd021770
Subject(s) - interglacial , holocene , geology , ice core , glacial period , climatology , ice sheet , oceanography , quaternary , paleoclimatology , precipitation , snow , atmospheric sciences , climate change , geomorphology , paleontology , geography , meteorology
Abstract Measurements of the 17 O excess of H 2 O were obtained from ice cores in West and East Antarctica. Combined with previously published results from East Antarctica, the new data provide the most complete spatial and temporal view of Antarctic 17 O excess to date. There is a steep spatial gradient of 17 O excess in present‐day precipitation across Antarctica, with higher values in marine‐influenced regions and lower values in the East Antarctic interior. There is also a spatial pattern to the change in 17 O excess between the Last Glacial Maximum (LGM) and Holocene periods. At coastal locations, there is no significant change in 17 O excess . At both the West Antarctic Ice Sheet Divide site and at Vostok, East Antarctica, the LGM to Early Holocene change in 17 O excess is about 20 per meg. Atmospheric general circulation model (GCM) experiments show that both the observed spatial gradient of 17 O excess in modern precipitation, and the spatial pattern of LGM to Early Holocene change, can be explained by kinetic isotope effects during snow formation under supersaturated conditions, requiring a high sensitivity of supersaturation to temperature. The results suggest that fractionation during snow formation is the primary control on 17 O excess in Antarctic precipitation. Variations in moisture source relative humidity play a negligible role in determining the glacial‐interglacial 17 O excess changes observed in Antarctic ice cores. Additional GCM experiments show that sea ice expansion increases the area over which supersaturating conditions occur, amplifying the effect of colder temperatures. Temperature and sea ice changes alone are sufficient to explain the observed 17 O excess glacial‐interglacial changes across Antarctica.