The Southern Ocean surface between Marine Isotope Stages 6 and 5d: Shape and timing of climate changes
The Southern Ocean surface between Marine Isotope Stages 6 and 5d: Shape and timing of climate changes
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海洋同位素第 6 阶段和第 5d 阶段之间的南大洋表面：气候变化的形状和时间
DOI：
10.1016/s0031-0182(02)00516-3
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
R. Gersonde
中科院分区：
文献类型：
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作者：
C. Bianchi;R. Gersonde
本文给出了大西洋和西印度洋南极带从末端II和末次间冰期S.S.恢复的7个岩心的夏季海表面温度(Ssst)和海冰范围，从千年到百年的分辨率，即海洋同位素5E阶段。基于硅藻的SSST估计表明，在MIS6晚期，威德尔海的冷水出口加剧，导致大西洋中部和东部的SSST接近0°C。由于冬季海冰边缘向北扩展3-5°纬度，海冰季节性减弱。这样的条件很有可能全年有效地减少海-气交换和冰川二氧化碳的减少。终止点II的增暖始于132-131ka，以海冰边缘的快速退缩为标志。Ssst在几千年内增加，在最早的MIS5e(128-125ka)达到间冰期夏季最高温度，范围在2.5至3.5℃之间。除了在129.5 ka左右发生明显的冷逆转外，增温还被短暂的温度反弹打断，其幅度为1-1.5℃，发生在200年-300年的频率范围内，因此属于太阳输入的周期性范围。增加角毛藻的数量。丰度表明，融水事件是造成酷林的主要原因。以生物沉积速率显著提高为特征的Ssst最佳期结束于约125ka，全球传送带完全重建，北半球气候最佳期开始。此时，SSST逐渐减少，并在比今天略暖的数值上稳定下来，在随后的MIS5e期间只显示出低幅度的振荡。在MIS5d期间，海冰场向北扩张，但SSST仅比现代略低，经向温度梯度减弱，表明南大洋并未处于真正的冰川模式。南大洋海温和冬季海冰记录以及Vostok大气温度和CO2记录之间的密切相关支持了南极冬季海冰和南大洋温度对大气-海洋CO2交换从而对全球气候起主要控制作用的观点。南极海冰场的减少和终止II开始时海温的增加可能是由影响南高纬度夏季日照的岁差变化引起的。正反馈机制、地表反照率的减少和二氧化碳向大气的释放，以及全球海洋环流的变化，受北大西洋深水(NADW)产量的崩溃或大幅减少的影响，可能会导致南大洋变暖的进一步加剧。
Summer sea surface temperature (SSST) and sea-ice extent, obtained at millennial to centennial resolution, are presented for seven cores recovered in the Atlantic and western Indian Antarctic Zone, from Termination II and the last interglacial s.s., i.e. Marine Isotope Substage (MIS) 5e. The diatom-based SSST estimates show that during the late MIS 6 intensified export of cold waters from the Weddell Sea resulted in SSSTs close to 0°C in the central and eastern Atlantic sector. Due to northward expansion of the winter sea-ice edge by 3–5° latitude the sea-ice seasonality was reduced. Such conditions have great potential for efficient year-round reduction in air–sea gas exchange and glacial CO2draw down. The warming at Termination II started at 132–131 ka, marked by rapid retreat of the sea-ice edge. The SSST increased within a few thousands of years to reach maximum interglacial summer temperatures ranging between 2.5 and 3.5°C, in the earliest MIS 5e (128–125 ka). Besides a distinct cold reversal around 129.5 ka, the warming was punctuated by short-lived temperature rebounds with amplitudes of 1–1.5°C, occurring at 200–300-yr frequency, thus in the range of the periodicity of solar input. Increased Chaetoceros spp. abundance suggests meltwater events as the primary cause of the coolings. The SSST optimum, characterised by strongly enhanced biogenic sedimentation rates, ended at ca. 125 ka, with the full re-establishment of the global conveyor belt and beginning of the Northern Hemisphere climatic optimum. At this time SSSTs decreased stepwise and stabilised on values slightly warmer than today, showing in the following period of MIS 5e only low amplitude oscillations. During MIS 5d a northward expansion of the sea-ice field took place, but SSSTs only slightly colder than modern ones and a weakened meridional temperature gradient indicate that the Southern Ocean did not fall in a true glacial mode. The tight correlation between Southern Ocean SSST and winter sea-ice records, and Vostok atmospheric temperature and CO2records support the idea that the Antarctic winter sea-ice and Southern Ocean temperature exert a primary control on the atmospheric–ocean CO2exchanges and hence on global climate. Reduction of the Antarctic sea-ice field and increase of SSST at the onset of Termination II could have been triggered by precessional changes influencing southern high latitude summer insolation. Positive feedback mechanisms, reduction of surface albedo and release of CO2into the atmosphere, and changes in global ocean circulation, affected by a collapse or strong reduction in North Atlantic Deep Water (NADW) production, could have induced further reinforcement of the Southern Ocean warming.