Triple water‐isotopologue record from WAIS Divide, Antarctica: Controls on glacial‐interglacial changes in 17Oexcess of precipitation
Triple water‐isotopologue record from WAIS Divide, Antarctica: Controls on glacial‐interglacial changes in 17Oexcess of precipitation
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DOI：
10.1002/2014jd021770
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发表时间：
2014-07
期刊：
影响因子：
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通讯作者：
S. Schoenemann;E. Steig;Q. Ding;Bradley R. Markle;A. Schauer
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作者：
S. Schoenemann;E. Steig;Q. Ding;Bradley R. Markle;A. Schauer
对东南极和西南极冰芯中的17 O过量H2O进行了测量。结合以前发表的东南极洲的结果，新数据提供了迄今为止最完整的南极17 Oexcess的时空视图。目前南极洲的降水量有一个陡峭的17 O过量的空间梯度，海洋影响区的值较高，东南极内陆的值较低。末次盛冰期（LGM）和全新世时期之间的17 O过量的变化也有一个空间格局。在沿海地区，17 O过量没有显著变化。在南极洲西部冰盖分水岭和南极洲东部的沃斯托克，末次冰期到全新世早期的17 O过量变化约为每兆20。大气环流模式（GCM）的实验表明，无论是在现代降水中观测到的17 O过量的空间梯度，和LGM的空间格局的变化，早全新世，可以解释动力学同位素效应在积雪形成过程中的过饱和条件下，需要一个高灵敏度的过饱和温度。结果表明，雪形成过程中的分馏是南极降水中17 O过量的主要控制因素。水分源相对湿度的变化在确定南极冰芯中观测到的冰期-间冰期17 O过量变化方面起着微不足道的作用。额外的GCM实验表明，海冰扩张增加了过饱和条件发生的区域，放大了较冷温度的影响。温度和海冰变化本身就足以解释南极洲观测到的17 O过量冰川-间冰期变化。
Measurements of the 17Oexcess of H2O 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 17Oexcess to date. There is a steep spatial gradient of 17Oexcess 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 17Oexcess between the Last Glacial Maximum (LGM) and Holocene periods. At coastal locations, there is no significant change in 17Oexcess. At both the West Antarctic Ice Sheet Divide site and at Vostok, East Antarctica, the LGM to Early Holocene change in 17Oexcess is about 20 per meg. Atmospheric general circulation model (GCM) experiments show that both the observed spatial gradient of 17Oexcess 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 17Oexcess in Antarctic precipitation. Variations in moisture source relative humidity play a negligible role in determining the glacial‐interglacial 17Oexcess 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 17Oexcess glacial‐interglacial changes across Antarctica.