Climate sensitivity to Arctic seaway restriction during the early Paleogene
Climate sensitivity to Arctic seaway restriction during the early Paleogene
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DOI：
10.1016/j.epsl.2009.07.026
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发表时间：
2009-09
影响因子：
5.3
通讯作者：
C. Roberts;A. Legrande;A. Tripati
中科院分区：
文献类型：
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作者：
C. Roberts;A. Legrande;A. Tripati
海洋门户的开启和关闭影响着全球热、盐和水分的分布，潜在地推动了区域到全球尺度的气候变化。6500万到4500万年前，在古近纪早期，北极和全球海洋之间的交换通过两条狭窄而浅的海道进行，格陵兰-挪威海道和图尔盖海峡。来自北冰洋的沉积物表明，在这段时间内，海洋表面是温暖的、微咸的，并且偶尔使淡水蕨类植物杜鹃花开花。导致北极古近纪这些条件发展的确切机制仍不确定。在这里，我们展示了一个同位素驱动的大气-海洋环流模型的结果，该模型表明北半球的气候对通过北极海道的海洋交换程度非常敏感。我们还提出了古近系海水和方解石δ18O的模拟估计。通过限制这些航道，我们模拟了北冰洋表面的新鲜到~6 psu，北大西洋海面温度变暖2°C，拉布拉多海海面温度变暖5-10°C。我们的研究结果可能有助于解释始新世期间北冰洋耐低盐度分类群的出现，并为西北大西洋的增温提供了机制。我们提出，格陵兰岛和欧洲之间火山陆桥的形成可能导致海洋对流增加和大西洋中间水域变暖。如果这是真的，这一结果与深海测量变化可能导致甲烷包合物热不稳定的理论是一致的，并支持古新世始新世热极大期（PETM）的构造触发假说。
The opening and closing of ocean gateways affects the global distribution of heat, salt, and moisture, potentially driving climatic change on regional to global scales. Between 65 and 45 million years ago (Ma), during the early Paleogene, exchange between the Arctic and global oceans occurred through two narrow and shallow seaways, the Greenland–Norway seaway and the Turgai Strait. Sediments from the Arctic Ocean suggest that, during this interval, the surface ocean was warm, brackish, and episodically enabled the freshwater fern Azolla to bloom. The precise mechanisms responsible for the development of these conditions in the Paleogene Arctic remain uncertain. Here we show results from an isotope-enabled, atmosphere-ocean general circulation model, which indicate that Northern Hemisphere climate would have been very sensitive to the degree of oceanic exchange through the Arctic seaways. We also present modelled estimates of seawater and calcite δ18O for the Paleogene. By restricting these seaways, we simulate freshening of the surface Arctic Ocean to ~6 psu and warming of sea-surface temperatures by 2 °C in the North Atlantic and 5–10 °C in the Labrador Sea. Our results may help explain the occurrence of low-salinity tolerant taxa in the Arctic Ocean during the Eocene and provide a mechanism for enhanced warmth in the north western Atlantic. We propose that the formation of a volcanic land-bridge between Greenland and Europe could have caused increased ocean convection and warming of intermediate waters in the Atlantic. If true, this result is consistent with the theory that bathymetry changes may have caused thermal destabilisation of methane clathrates and supports a tectonic trigger hypothesis for the Paleocene Eocene Thermal Maximum (PETM).