Ice core evidence for secular variability and 200-year dipolar oscillations in atmospheric circulation over East Antarctica during the Holocene
Ice core evidence for secular variability and 200-year dipolar oscillations in atmospheric circulation over East Antarctica during the Holocene
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全新世期间东南极洲大气环流长期变化和 200 年偶极振荡的冰芯证据
DOI：
10.1007/s00382-005-0012-9
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
R. Udisti
中科院分区：
文献类型：
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作者：
B. Delmonte;J. Petit;G. Krinner;V. Maggi;J. Jouzel;R. Udisti
分析了南极东部的两个全新世冰芯记录(Vostok和EPICA-Dome C)在每50年1个样本的时间分辨率下的尘埃浓度和粒度分布。一系列火山标志物随机分布在冰芯的公共部分(从9.8到3.5年BP)，确保了准确的相对测年(±33年)。这两个地点的尘埃大小记录显示了周期性的振荡，其亚千年和长期尺度的频率显然是不同步的。两个尘埃尺度记录的合成和(Σ)的功率谱大多表现出150-500年的周期谱能量。另一方面，200年波段是两个记录的共同之处，两个地点的200年成分在~5.5年以上是异相的(100年领先或滞后)，这一现象也反映在显著的(>；99%conf)。Lev.)两种大小记录的合成差值(Δ)的功率谱中的频带。在长距离输送过程中，源自南半球大陆的矿物粉尘根据大气输送的海拔高度和持续时间不同程度地进行分级。相对较粗的尘埃与来自对流层中下部的气团穿透有关，相反，相对较细的尘埃与对流层上层气团或南极高原上的下沉影响有关，这一假说已经就最后一次冰盛期向全新世过渡期间发生的变化提出了假说(Delmonte等人)。2004b)。此外，我们假设南极洲上空大气质量平流的总体波动取决于相对于低纬的经向气压梯度，即南极涛动(AAO)。因此，我们认为东南极洲上空的大气环流存在区域变异性。综合(Σ)参数的150-500年功率谱代表了AAO的长期变率，可能与南方海洋-气候系统有关的长期内部振荡留下了印记。另一方面，Δ尘埃综合参数表明，南极东部上空存在一个持续的大气偶极子，以两个百年的周期交替向东半球和穹顶C地区输送较粗(较细)的尘埃粒子。事实上，在最后一次冰川消融期间，已经在南极东部的三个地点观察到了尘埃粒度分布的拉锯现象(Delmonte等人)。2004b)，并被解释为极地涡旋相对于地理南极的偏心程度逐渐减小。有趣的是，Δ参数显示了一个明显的200年振荡模式，为气候和太阳活动之间可能存在的关系这一悬而未决的问题提供了新的线索。
Two Holocene ice core records from East Antarctica (Vostok and EPICA-Dome C) were analysed for dust concentration and size distribution at a temporal resolution of 1 sample per ~50 years. A series of volcanic markers randomly distributed over the common part of the ice cores (from 9.8 to 3.5 kyear BP) ensures accurate relative dating (±33 years). Dust-size records from the two sites display oscillations structured in cycles with sub-millennial and secular scale frequencies that are apparently asynchronous. The power spectra of the composite sum (Σ) of the two dust-size records display spectral energy mostly for 150- to 500-year periodicities. On the other hand, the 200-year band is common to both records and the 200 year components of the two sites are out-of-phase (100-year lead or lag) over ~5.5 kyear, a phenomenon also reflected by a significant (>99% conf. lev.) band in the power spectra of the composite difference (Δ) of the two size records. During long-range transport, mineral dust originating from the Southern Hemisphere continents is graded to a variable extent depending on the altitude and duration of atmospheric transport. Relatively coarse dust is associated with air mass penetration from the middle–lower troposphere and conversely relatively fine dust with upper troposphere air masses or the influence of subsidence over the Antarctic plateau, a hypothesis already proposed for the changes that occurred during the Last Glacial Maximum to Holocene transition (Delmonte et al. 2004b). Moreover, we assume that the overall fluctuation of air mass advection over Antarctica depends on the meridional pressure gradient with respect to low latitudes, i.e. the Antarctic Oscillation (AAO). We therefore suggest a regional variability in atmospheric circulation over East Antarctica. The 150–500 year power spectrum of the composite (Σ) parameter represents the long term variability of the AAO, imprinted by secular internal oscillations probably related to the southern ocean-climatic system. On the other hand, the Δ dust composite parameter suggests a persistent atmospheric dipole over East Antarctica delivering coarser (finer) dust particles alternatively to Vostok and Dome C regions with a bi-centennial periodicity. Indeed, a seesaw phenomenon in dust size distribution was already observed at three East Antarctic sites during the last deglaciation (Delmonte et al. 2004b) and was interpreted as a progressive reduction of the eccentricity of the polar vortex with respect to the geographic south pole. Interestingly, the Δ parameter shows a pronounced 200-year oscillation mode, throwing new light on the unresolved question of a possible relationship between climate and solar activity.