Firn-air δ15N in modern polar sites and glacial–interglacial ice: a model-data mismatch during glacial periods in Antarctica?
Firn-air δ15N in modern polar sites and glacial–interglacial ice: a model-data mismatch during glacial periods in Antarctica?
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DOI：
10.1016/j.quascirev.2005.06.007
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发表时间：
2006
影响因子：
4
通讯作者：
A. Landais;J. Barnola;K. Kawamura;N. Caillon;M. Delmotte;T. Ommen;G. Dreyfus;J. Jouzel;V. Masson‐Delmotte;B. Minster;J. Freitag;M. Leuenberger;J. Schwander;C. Huber;D. Etheridge;V. Morgan
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文献类型：
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作者：
A. Landais;J. Barnola;K. Kawamura;N. Caillon;M. Delmotte;T. Ommen;G. Dreyfus;J. Jouzel;V. Masson‐Delmotte;B. Minster;J. Freitag;M. Leuenberger;J. Schwander;C. Huber;D. Etheridge;V. Morgan
大气成分（气泡）和温度（水同位素）之间的相位滞后可以从冰芯中量化，前提是可以正确估计被困空气和周围空气之间的年龄差。这种差异取决于空气不再与大气混合的锁定深度（LID）。LID可通过确化模型或空气同位素组成（δ15N和δ40Ar）估算。这两种方法对格陵兰岛和南极洲的一个沿海地点给出了一致的结果（伯德）。在格陵兰岛（NorthGRIP）和南极洲（Berkner Island, BAS depot, Dome C）进行的新firn测量证实，在大范围的地表条件下，固化模型正确地再现了当前的LID。然而，在南极东部站点（Vostok、Dome C、Dome F）观测到的末次盛冰期（LGM）存在系统性失配，质疑了模型的有效性。在这里，我们使用了两个南极沿海站点（Kohnen站和Law Dome站）的新δ15N测量值，提供了与确证模型计算不同的深度估计。我们表明，这种差异可以通过修正过去积累率的估计来解决。因此，δ15N测量有助于限制过去的积累速率和改进冰芯定年。
The phase lag between atmospheric composition (air bubbles) and temperature (water isotopes) can be quantified from ice cores provided that the age difference between entrapped air and the surrounding air can be correctly estimated. This difference depends on the lock-in depth (LID), when air no longer mixes with the atmosphere. The LID can be estimated from firnification models or from the air isotopic composition (δ15N and δ40Ar). Both methods give consistent results for Greenland and one coastal site in Antarctica (Byrd). New firn measurements in Greenland (NorthGRIP) and Antarctica (Berkner Island, BAS depot, Dome C) confirm that firnification models correctly reproduce the present LID over a large range of surface conditions. However, a systematic mismatch is observed for the Last Glacial Maximum (LGM) in East Antarctic sites (Vostok, Dome C, Dome F) questioning the model's validity. Here we use new δ15N measurements from two coastal Antarctic sites (Kohnen Station and Law Dome) providing depth estimates again distinct from firnification model calculations. We show that this discrepancy can be resolved by revising the estimate of past accumulation rates. δ15N measurements can therefore help to constrain past accumulation rate and improve ice core dating.