The effect of the East Atlantic pattern on the precipitation δ18O-NAO relationship in Europe
The effect of the East Atlantic pattern on the precipitation δ18O-NAO relationship in Europe
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DOI：
10.1007/s00382-015-2950-1
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发表时间：
2016-10-01
期刊：
影响因子：
4.6
通讯作者：
Werner, M.
中科院分区：
文献类型：
--
作者：
Comas-Bru, L.;McDermott, F.;Werner, M.
已知北大西洋涛动（NAO）通过控制气温和在北方冬季将水分带到欧洲的西风的轨迹来影响降水量Δ O-18（Δ O-18（p））。因此，试图重建NAO的古气候研究可以利用通常保存在石笋，冰芯，树木年轮和湖泊沉积物等自然档案中的三角洲O-18信号。然而，这样的重建应该考虑的不确定性，所产生的非平稳性在三角洲O-18（p）-NAO的关系。在这里，这些时间非平稳性的原因提出了新的见解，为欧洲地区使用的观测（GNIP数据库）和输出的同位素启用的大气环流模型（ECHAM 5-wiso）。结果表明，尽管在仪器观测期间，东大西洋（EA）型与δ O-18（p）基本不相关，但EA型的极性影响δ O-18（p）-NAO关系。这种关系的非平稳性是由于不同的NAO/EA组合导致的δ O-18（p）-NAO相关区域的空间位移造成的。这些变化与先前报道的NAO冬季气候变量和由此产生的非平稳性意味着三角洲O-18为基础的NAO重建可能会受到损害，如果积极和消极的NAO/EA状态的平衡有很大的不同，在一个校准期间相比，在过去的利益。同样的方法也被用来评估δ O-18（p）与冬季总降水量和冬季平均地面气温之间的关系，得到了类似的结果。至关重要的是，这项研究还确定了欧洲地区的NAO，气温和降水的时间变化可以更强大的重建使用三角洲O-18时间序列从自然档案，无论伴随的变化在EA。
The North Atlantic Oscillation (NAO) is known to influence precipitation delta O-18 (delta O-18(p)) through its control on air temperature and on the trajectory of the westerly winds that carry moisture onto Europe during boreal winters. Hence, paleoclimate studies seeking to reconstruct the NAO can exploit the delta O-18 signal that is commonly preserved in natural archives such as stalagmites, ice cores, tree rings and lake sediments. However, such reconstructions should consider the uncertainties that arise from non-stationarities in the delta O-18(p)-NAO relationship. Here, new insights into the causes of these temporal non-stationarities are presented for the European region using both observations (GNIP database) and the output of an isotope-enabled general circulation model (ECHAM5-wiso). The results show that, although the East Atlantic (EA) pattern is generally uncorrelated to delta O-18(p) during the instrumental period, its polarity affects the delta O-18(p)-NAO relationship. Non-stationarities in this relationship result from spatial shifts of the delta O-18(p)-NAO correlated areas as a consequence of different NAO/EA combinations. These shifts are consistent with those reported previously for NAO-winter climate variables and the resulting non-stationarities mean that delta O-18-based NAO reconstructions could be compromised if the balance of positive and negative NAO/EA states differs substantially in a calibration period compared with the period of interest in the past. The same approach has been followed to assess the relationships between delta O-18(p) and both winter total precipitation and winter mean surface air temperature, with similar results. Crucially, this study also identifies regions within Europe where temporal changes in the NAO, air temperature and precipitation can be more robustly reconstructed using delta O-18 time series from natural archives, irrespective of concomitant changes in the EA.