Abrupt cold events in the North Atlantic Ocean in a transient Holocene simulation
Abrupt cold events in the North Atlantic Ocean in a transient Holocene simulation
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DOI：
10.5194/cp-14-1165-2018
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发表时间：
2017-09
影响因子：
4.3
通讯作者：
Andrea Klus;M. Prange;V. Varma;L. Tremblay;M. Schulz
中科院分区：
文献类型：
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作者：
Andrea Klus;M. Prange;V. Varma;L. Tremblay;M. Schulz
抽象的。从全新世以来，在北大西洋的许多气候记录中已经发现了突然的寒冷事件。已经讨论了几种可能触发这些持续数十年至数百年的气候变化的机制。在这里，我们描述了两个突然的冷事件发生在轨道强迫瞬变全新世模拟使用社区气候系统模型版本3。这两个事件都发生在全新世晚期（事件1和事件2分别为4305 - 4267 BP和3046 - 3018 BP）。这两次冷事件的特点是地表大幅冷却（分别为-2.3和-1.8 °C）和淡化（分别为-0.6和-0.5 PSU），纽芬兰岛以东和格陵兰岛以南的海冰严重推进，在冷事件的高潮时远达东北大西洋的冰岛海盆。西北大西洋的对流和深水形成在风暴期间崩溃，而大西洋经向翻转环流没有受到实质性影响（分别仅减弱约10%和5%）。引发这些事件的原因是北大西洋正振荡的长时间阶段，造成副极地海洋环流和相关淡水输送发生重大变化，导致副极地环流减弱。我们的研究结果提出了一种可能的机制，通过这种机制，北大西洋地区的突然寒冷事件可能是由内部气候变率触发的，而不需要外部（例如，太阳或火山）强迫。
Abstract. Abrupt cold events have been detected in numerous North Atlantic climate records from the Holocene. Several mechanisms have been discussed as possible triggers for these climate shifts persisting decades to centuries. Here, we describe two abrupt cold events that occurred during an orbitally forced transient Holocene simulation using the Community Climate System Model version 3. Both events occurred during the late Holocene (4305–4267 BP and 3046–3018 BP for event 1 and event 2, respectively). They were characterized by substantial surface cooling (−2.3 and −1.8 ∘C, respectively) and freshening (−0.6 and −0.5 PSU, respectively) as well as severe sea ice advance east of Newfoundland and south of Greenland, reaching as far as the Iceland Basin in the northeastern Atlantic at the climaxes of the cold events. Convection and deep-water formation in the northwestern Atlantic collapsed during the events, while the Atlantic Meridional Overturning Circulation was not substantially affected (weakening by only about 10 % and 5 %, respectively). The events were triggered by prolonged phases of a positive North Atlantic Oscillation that caused substantial changes in the subpolar ocean circulation and associated freshwater transports, resulting in a weakening of the subpolar gyre. Our results suggest a possible mechanism by which abrupt cold events in the North Atlantic region may be triggered by internal climate variability without the need of an external (e.g., solar or volcanic) forcing.