Phase relationships between orbital forcing and the composition of air trapped in Antarctic ice cores
Phase relationships between orbital forcing and the composition of air trapped in Antarctic ice cores
复制标题
DOI：
10.5194/cp-12-729-2016
复制
发表时间：
2016-01-01
影响因子：
4.3
通讯作者：
Pric, Frederic
中科院分区：
文献类型：
--
作者：
Bazin, Lucie;Landais, Amaelle;Pric, Frederic
轨道调谐对于超出年层计数的冰芯年代学至关重要，格陵兰冰芯可追溯到6万年前（即1950年之前的数千年）。虽然最近利用δ¹⁸O(atm)、δO₂/N₂和含气量并针对不同轨道目标开发了几种互补的轨道调谐工具，但量化它们的不确定性仍然是一个挑战。事实上，将在冰中捕获的空气中测量的这些参数的变化与其轨道目标联系起来的确切过程尚未完全理解。在此，我们提供了新的δO₂/N₂和δ¹⁸O(atm)数据系列，涵盖海洋同位素阶段（MIS）5（10万到16万年之间）以及东南极冰芯欧洲南极冰芯计划 Dome C（EDC）最古老的部分（34万 - 80万年）。首次针对MIS 5的测量使得能够对来自三个东南极冰芯站点（EDC、东方站和富士 Dome）的δO₂/N₂和δ¹⁸O(atm)记录进行相互比较。这种比较凸显了一些特定站点的δO₂/N₂变化。这样的观测结果，即δO₂/N₂信号中10万年周期性的证据，以及难以确定δO₂/N₂的极值和中坡，增加了将δO₂/N₂用作轨道调谐工具的相关不确定性，现在计算为3 - 4万年。当结合来自东方站和EDC的δ¹⁸O(atm)和δO₂/N₂记录时，我们发现在最小偏心率时期（约40万年、72万 - 80万年）这两个参数的轨道特征缺失。我们的数据集揭示了过去80万年中δO₂/N₂和δ¹⁸O(atm)记录之间随时间变化的偏移，我们将其解释为δ¹⁸O(atm)对岁差的滞后响应的变化。最大的偏移出现在第二终止期、MIS 8和MIS 16，对应于北极冰盖不稳定的时期。因此，我们认为类似海因里希事件的发生影响了δ¹⁸O(atm)对岁差的响应。
Orbital tuning is central for ice core chronologies beyond annual layer counting, available back to 60 ka (i.e. thousands of years before 1950) for Greenland ice cores. While several complementary orbital tuning tools have recently been developed using delta O-18(atm), delta O-2/N-2 and air content with different orbital targets, quantifying their uncertainties remains a challenge. Indeed, the exact processes linking variations of these parameters, measured in the air trapped in ice, to their orbital targets are not yet fully understood. Here, we provide new series of delta O-2/N-2 and delta O-18(atm) data encompassing Marine Isotopic Stage (MIS) 5 (between 100 and 160 ka) and the oldest part (340-800 ka) of the East Antarctic EPICA Dome C (EDC) ice core. For the first time, the measurements over MIS 5 allow an inter-comparison of delta O-2/N-2 and delta O-18(atm) records from three East Antarctic ice core sites (EDC, Vostok and Dome F). This comparison highlights some site-specific delta O-2/N-2 variations. Such an observation, the evidence of a 100 ka periodicity in the delta O-2/N-2 signal and the difficulty to identify extrema and mid-slopes in delta O-2/N-2 increase the uncertainty associated with the use of delta O-2/N-2 as an orbital tuning tool, now calculated to be 3-4 ka. When combining records of delta O-18(atm) and delta O-2/N-2 from Vostok and EDC, we find a loss of orbital signature for these two parameters during periods of minimum eccentricity (similar to 400 ka, 720-800 ka). Our data set reveals a time-varying offset between delta O-2/N-2 and delta O-18(atm) records over the last 800 ka that we interpret as variations in the lagged response of delta O-18(atm) to precession. The largest offsets are identified during Terminations II, MIS 8 and MIS 16, corresponding to periods of destabilization of the Northern polar ice sheets. We therefore suggest that the occurrence of Heinrich like events influences the response of delta O-18(atm) to precession.