Mid-Pliocene shifts in ocean overturning circulation and the onset of Quaternary-style climates
Mid-Pliocene shifts in ocean overturning circulation and the onset of Quaternary-style climates
复制标题
上新世中期海洋翻转环流的变化和第四纪气候的开始
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
D. Garbe‐Schönberg
中科院分区：
文献类型：
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作者：
M. Sarnthein;G. Bartoli;M. Prange;A. Schmittner;B. Schneider;M. Weinelt;N. Andersen;D. Garbe‐Schönberg
抽象的。地球历史的一个主要转折点发生在上新世中期：主要的北半球冰川作用（NHG）和明显的、前三代风格的冰川-间冰期气候周期的开始，这与之前新生代的大部分时间里更为均匀的气候形成对比，并持续到今天（Zachos等人，2001年）。在3.2 Ma（温暖MIS K3）和2.7 Ma（冰川MIS G6/4）之间，气候的严重恶化分三个阶段发生（Lisiecki和Raymo，2005年）。各种模型（感觉Drivel和Haug，1998年）和古海洋学记录（使用轨道年龄控制相互校准）表明，从加勒比和东太平洋之间盐度差异的上升推断，NHG的开始与中美洲航道最终关闭的三个步骤之间存在明确的联系。每次闭合事件都导致北大西洋纬向翻转环流增强，这加强了盐和热量的向极输送（升温+2-3°C）（Bartoli等人，2005年）。此外，关闭导致向欧亚大陆西北部的极地大气水分输送略有增加（Lunt等人，2007年），这可能导致降水量和河流径流量增加，海面盐度降低，北冰洋海冰覆盖面积增加，从而促进了北极冰和大陆冰盖的积累。最重要的是，新的证据表明，CAS的关闭导致北太平洋的空间高度更大，从而使从白令海峡到东格陵兰海流（EGC）的低盐度北极洋流增加了一倍。因此，拉布拉多海IODP站点1307显示出突然但不可逆的EGC冷却6°C，并从3.25/3.16-3.00 Ma清新约2 psu，就在第一次但仍然可逆的关闭CAS的尝试之后。
Abstract. A major tipping point of Earth's history occurred during the mid-Pliocene: the onset of major Northern-Hemisphere Glaciation (NHG) and of pronounced, Quaternary-style cycles of glacial-to-interglacial climates, that contrast with more uniform climates over most of the preceding Cenozoic and continue until today (Zachos et al., 2001). The severe deterioration of climate occurred in three steps between 3.2 Ma (warm MIS K3) and 2.7 Ma (glacial MIS G6/4) (Lisiecki and Raymo, 2005). Various models (sensu Driscoll and Haug, 1998) and paleoceanographic records (intercalibrated using orbital age control) suggest clear linkages between the onset of NHG and the three steps in the final closure of the Central American Seaways (CAS), deduced from rising salinity differences between Caribbean and the East Pacific. Each closing event led to an enhanced North Atlantic meridional overturning circulation and this strengthened the poleward transport of salt and heat (warmings of +2–3°C) (Bartoli et al., 2005). Also, the closing resulted in a slight rise in the poleward atmospheric moisture transport to northwestern Eurasia (Lunt et al., 2007), which probably led to an enhanced precipitation and fluvial run-off, lower sea surface salinity (SSS), and an increased sea-ice cover in the Arctic Ocean, hence promoting albedo and the build-up of continental ice sheets. Most important, new evidence shows that the closing of the CAS led to greater steric height of the North Pacific and thus doubled the low-saline Arctic Throughflow from the Bering Strait to the East Greenland Current (EGC). Accordingly, Labrador Sea IODP Site 1307 displays an abrupt but irreversible EGC cooling of 6°C and freshening by ~2 psu from 3.25/3.16–3.00 Ma, right after the first but still reversible attempt of closing the CAS.