Southern Hemisphere intermediate water formation and the bi-polar seesaw
Southern Hemisphere intermediate water formation and the bi-polar seesaw
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南半球中间水的形成和双极跷跷板
DOI：
10.22498/pages.18.1.36
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
R. Ganeshram
中科院分区：
文献类型：
--
作者：
Simon J. A. Jung;D. Kroon;G. Ganssen;F. Peeters;R. Ganeshram
在最后一个冰河期，盛行了千禧年规模的深刻气候变化。它首先在格陵兰岛冰芯中被发现，随后在全球范围内被记录下来，但控制这种变化的潜在机制尚未确定。半球间的异步性（称为双极跷跷板）加剧了这种快速气候变化的复杂性。解开千禧年尺度变异控制的一条重要线索来自葡萄牙附近的深海（Shackleton 等，2000）。在这里，表层浮游有孔虫的稳定氧同位素变化显示出与格陵兰岛气候变化的明显联系，而基于生活在海底的底栖有孔虫的相应记录则与南极气候变化有关，反映了葡萄牙附近大西洋深海普遍存在的南极底水的南部起源。气候异步性的一种可能机制涉及半球间热量储存的不平衡（Stocker 和 Johnsen，2003）。南大西洋的表层海洋记录（Barker 等，2009）确实显示了与格陵兰冰芯相反的气候变化模式，支持了异步热存储有助于抵消千年规模的北半球和南半球气候变化的观点。南源中层水的作用（南极中层水，图 1：现代海洋中 δ13C 的分布（根据 Charles 和 Fairbanks，1992 年重新绘制）。白色圆圈表示沉积物核心的位置 NIOP 905（印度洋；Jung 等，2009）、MD95-2042（大西洋；Shackleton 等，2000）和双极 AAIW 中的 MD97-2120（太平洋；Pahnke 和 Zahn，2005）由于其体积大和相关的能量存储容量而具有全球意义。然而，基于数据的证据很少。来自西南太平洋中深度的底栖稳定同位素数据（Pahnke 和 Zahn，2005）显示，在北大西洋寒冷的海因里希事件期间，冰川 AAIW 形成加剧。在海因里希事件期间，北大西洋周围的大型大陆冰块将冰山“船队”释放到海洋中。这些冰山的融化扰乱了北大西洋深水（NADW）的形成，从而减缓了大西洋的翻转环流。因此，来自西南太平洋的数据表明，当北大西洋翻转环流强烈时，西南太平洋的冰川AAIW形成加剧。 科学要点：开放剖面的结果可能是由于我们记录中的分辨率较低。另一方面，这一结果也提出了这样一个问题：ENSO敏感地区档案中的全新世气候信号是否包含非ENSO信号，例如季节性引起的热带辐合带迁移。大多数对过去与 ENSO 活动相关的气候参数变化的重建都没有考虑到过去季节性的潜在影响。然而，季节会对过去气候的地质记录产生相当大的影响（Leduc 等，2010；Laepple 和 Lohmann，2009）。我们强调，仔细检查没有季节性周期的海洋区域过去的水文变化记录，再加上在研究的时间间隔内收集全谱水文变率的采样策略，将有助于澄清哪种气候现象调节了地质记录中存档的一级气候信号。
During the last glacial period, a profound millennial-scale climate variation prevailed. First discovered in Greenland ice cores, it has subsequently been documented around the globe, yet the underlying mechanisms controlling this variability have not been indentified. Adding to the complexity of this rapid climate change is an interhemispheric asynchronicity, known as the bipolar seesaw. A significant clue towards unraveling the controls of millennialscale variability came from the deep ocean off Portugal (Shackleton et al., 2000). Here, stable oxygen isotope variability in surface dwelling planktic foraminifera shows clear ties to Greenland climate variability, whereas the respective record based on benthic foraminifers living on the seafloor relates to Antarctic climate variation, reflecting the southern origin of the Antarctic Bottom Water that prevails in the abyssal Atlantic off Portugal. One likely mechanism for the climatic asynchronicity involves an interhemispheric imbalance in heat storage (Stocker and Johnsen, 2003). Surface ocean records from the South Atlantic Ocean (Barker et al., 2009) indeed show a climate change pattern opposed to that in Greenland ice cores supporting the view that asynchronous heat storage is instrumental in off-setting Northern and Southern Hemisphere climate change at the millennial-scale. The role of southern-source intermediate water (Antarctic Intermediate Water, Figure 1: Distribution of δC in the modern ocean (redrawn from Charles and Fairbanks, 1992). White circles indicate the location of sediment cores NIOP 905 (Indian Ocean; Jung et al., 2009), MD95-2042 (Atlantic Ocean; Shackleton et al., 2000) and MD97-2120 (Pacific Ocean; Pahnke and Zahn, 2005). AAIW) in the bipolar seesaw is of global relevance due to its large volume and associated energy storage capacity. However, data-based evidence is rare. Benthic stable isotope data from the intermediate depth SW Pacific (Pahnke and Zahn, 2005) show periods of intensified glacial AAIW formation during the cold Heinrich Events in the North Atlantic. During Heinrich Events, the large continental ice masses surrounding the North Atlantic released “flotillas” of icebergs into the ocean. The melting of these icebergs disrupted the formation of North Atlantic Deep Water (NADW) and hence slowed down the overturning circulation in the Atlantic. Thus the data from the SW Pacific suggest that glacial AAIW formation was intensified in the SW Pacific during a time when the overturning circulation in the North Atlantic was strongly Sc ie nc e H ig hl ig ht s: O pe n Se ct io n sult can potentially be due to the low resolution in our record. On the other hand, this result also raises the question whether Holocene climatic signals from archives in ENSO-sensitive regions contain non-ENSO signals, such as seasonally-induced InterTropical Convergence Zone migrations. Most reconstructions of past changes in climatological parameters linked to ENSO activity do not account for the potential impact of past seasonality. Yet seasons can have a considerable impact on the geological record of past climate (Leduc et al., 2010; Laepple and Lohmann, 2009). We emphasize that a careful examination of records of past hydrological changes from oceanic regions without seasonal cycles, together with sampling strategies collecting the full spectrum of hydrological variability within the time intervals studied, would help to clarify which climatic phenomenon modulates the first-order climatic signal archived in geological records.
影响因子：
5.3
作者：
Jung, Simon J. A.;Kroon, Dick;Ganeshram, Raja
通讯作者：
Ganeshram, Raja