The Bering Strait is grip on the northern hemisphere climate
The Bering Strait is grip on the northern hemisphere climate
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DOI：
10.1016/j.dsr.2004.05.003
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发表时间：
2004-10-01
影响因子：
2.4
通讯作者：
Nof, D
中科院分区：
文献类型：
--
作者：
De Boer, AM;Nof, D
在过去的10,000年里，气候明显稳定。在早冰期（125，000年前），气候记录显示了长期的大振幅振荡，通常称为Dansgaard-Oeschger（D/O）或Heinrich事件。这些波动被认为是北大西洋淡水异常的结果，这大大减少了纬向翻转环流（MOC）的输送。随后是主运行中心的恢复。在这里，我们建议，这种长期持续的不稳定性，在纬向环流是唯一可能在冰期时，白令海峡（BS）是关闭的。一个分析海洋模式，其中包括风和温盐过程）被用来表明，在间冰期（当BS是开放的）扰动在北大西洋深水（NADW）形成迅速衰减。这种新的机制涉及到南大洋（SO）的强风，它具有开放的BS，迅速[O（1-10年）]将任何大的低盐度异常从大西洋冲到太平洋。在冰川期，稳定作用被BS的关闭所阻止，BS将异常捕获在大西洋内，造成长期持续的扰动。我们还表明，没有连续的淡水通量是需要的，以保持崩溃的MOC从一个封闭的盆地的情况下恢复，但需要一个相对较大的连续通量0.19 Sv，以保持崩溃状态在开放BS的情况下。随着淡水运输量的减少，开放的主运行中心很快恢复。这也表明开放BS比封闭BS情况更稳定。面向过程的数值模拟，使用理想化的几何形状在两层海洋支持我们的解析解，并表明冲洗机制是积极的，即使当浅BS窗台。(C)2004爱思唯尔有限公司保留所有权利。
The last 10,000 years have been characterized by distinctly stable climates. For the earlier glacial period (up to 125,000 years ago), climate records show long-lasting large-amplitude oscillations, generally known as Dansgaard-Oeschger (D/O) or Heinrich events. These fluctuations are believed to be a result of freshwater anomalies in the North Atlantic which dramatically reduce the transport of the meridional overturning cell (MOC). They are followed by a recovery of the MOC. Here, we propose that such long lasting instabilities in the meridional circulation are only possible during glacial periods when the Bering Strait (BS) is closed. An analytical ocean model which includes both wind and thermohaline processes) is used to show that, during interglacial periods (when the BS is open) perturbations in North Atlantic Deep Water (NADW) formation are quickly damped out. This new mechanism involves the strong winds in the Southern Ocean (SO) which, with an open BS, quickly [O(1-10 years)] flush any large low salinity anomalies out of the Atlantic and into the Pacific Ocean. During glacial periods, the stabilizing effect is prevented by the closure of the BS which traps the anomalies within the Atlantic, causing long lasting perturbations. We also show that no continuous fresh-water flux is needed in order to keep the collapsed MOC from a recovery in the closed basin case, but a relatively large continuous flux of 0.19 Sv is required in order to keep the collapsed state in the open BS case. With a smaller freshwater transport, the open MOC quickly recovers. This also indicates that an open BS is more stable than the closed BS case. Process-oriented numerical simulations using idealized geometry in a two-layer ocean support our analytical solutions and show that the flushing mechanism is active even when the shallow BS sill is included. (C) 2004 Elsevier Ltd. All rights reserved.