Oceanographic and climatic evolution of the southeastern subtropical Atlantic over the last 3.5 Ma
Oceanographic and climatic evolution of the southeastern subtropical Atlantic over the last 3.5 Ma
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近3.5 Ma东南副热带大西洋海洋和气候演变
DOI：
10.1016/j.epsl.2018.03.054
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发表时间：
2018
影响因子：
5.3
通讯作者：
R. Pancost
中科院分区：
文献类型：
--
作者：
B. Petrick;E. McClymont;K. Littler;A. Rosell‐Melé;M. Clarkson;M. Maslin;U. Röhl;A. Shevenell;R. Pancost
东南大西洋主要由两个大洋系统构成：本格拉上升流系统和阿古拉斯渗漏系统。本格拉上升流系统是世界上生产力最高的沿岸上升流系统之一，它对印度洋向大西洋输送暖咸水起着重要作用。在这里，我们呈现了来自ODP1087站点的海洋沉积物的多代理记录。我们重建了海洋表面温度(U 37K‘和TeX 86指数)、海洋初级生产力(总氯素和烯酮质量累积率)和来自南部非洲的陆地输入(通过XRF扫描得到的钛/铝和钙/钛)，以了解东南大西洋自上新世晚期以来的演化。在上新世晚期和更新世早期，ODP1087站位于本格拉上升流系统内，相对于现今，本格拉上升流系统向南移动。我们在代理记录中发现了3.3、3.0、2.2、1.5、0.9和0.6 Ma的一系列事件，这些事件被解释为反映了主要全球风和海洋系统位置的变化以及风的强度和/或位置的局部变化，这些变化影响了养分的有效性。虽然在北半球冰川开始(InHg)附近观察到了暂时的SST冷却，但来自ODP1087站的替代记录显示，在2.7 Ma左右没有明显的气候转变，相反，大多数变化发生在这个时间之前。这一观察结果意义重大，因为以前曾有人建议，与这种气候转变相关的上升流的位置和/或强度应该发生变化。相反，ODP1087站的主位移发生在0.9 Ma和0.6 Ma左右，与中更新世早期的过渡有关，明显丧失了以前以上升流为主的体制。这一观察结果提出了这样一种可能性，即东南大西洋环流向现代条件的重组与EMPT密切相关，而不是与更早的气候转变有关。
Abstract The southeast Atlantic Ocean is dominated by two major oceanic systems: the Benguela Upwelling System, one of the world's most productive coastal upwelling cells and the Agulhas Leakage, which is important for transferring warm salty water from the Indian Ocean to the Atlantic Ocean. Here, we present a multi-proxy record of marine sediments from ODP Site 1087. We reconstruct sea surface temperatures (U 37 K′ and TEX 86 indices), marine primary productivity (total chlorin and alkenone mass accumulation rates), and terrestrial inputs derived from southern Africa (Ti/Al and Ca/Ti via XRF scanning) to understand the evolution of the Southeast Atlantic Ocean since the late Pliocene. In the late Pliocene and early Pleistocene, ODP Site 1087 was situated within the Benguela Upwelling System, which was displaced southwards relative to present. We recognize a series of events in the proxy records at 3.3, 3.0, 2.2, 1.5, 0.9 and 0.6 Ma, which are interpreted to reflect a combination of changes in the location of major global wind and oceanic systems and local variations in the strength and/or position of the winds, which influence nutrient availability. Although there is a temporary SST cooling observed around the initiation of Northern Hemisphere glaciation (iNHG), proxy records from ODP Site 1087 show no clear climatic transition around 2.7 Ma but instead most of the changes occur before this time. This observation is significant because it has been previously suggested that there should be a change in the location and/or strength of upwelling associated with this climate transition. Rather, the main shifts at ODP Site 1087 occur at ca. 0.9 Ma and 0.6 Ma, associated with the early mid-Pleistocene transition (EMPT), with a clear loss of the previous upwelling-dominated regime. This observation raises the possibility that reorganisation of southeast Atlantic Ocean circulation towards modern conditions was tightly linked to the EMPT, but not to earlier climate transitions.
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影响因子：
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作者：
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Biastoch, A.;Boening, C. W.;Lutjeharms, J. R. E.
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