Pronounced zonal heterogeneity in Eocene southern high-latitude sea surface temperatures
Pronounced zonal heterogeneity in Eocene southern high-latitude sea surface temperatures
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DOI：
10.1073/pnas.1321441111
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发表时间：
2014-05-06
影响因子：
11.1
通讯作者：
Pagani, Mark
中科院分区：
文献类型：
--
作者：
Douglas, Peter M. J.;Affek, Hagit P.;Pagani, Mark
古气候研究表明始新世全球变暖在高纬度地区被大大放大，气候模式无法完全再现这种状态。然而，始新世近南极海表温度（sst）的代用估算在相似纬度上产生了截然不同的结果，西南太平洋的海表温度高于20℃，而南大西洋的海表温度在5至15℃之间。在这些地点应用的单个古温度代用物所固有的不确定性阻碍了这种纬向温差的验证。本文利用南极半岛附近Seymour岛的多代理数据，提供了始新世中晚期10-17℃（1 sigma SD）年海温的良好约束证据。Seymour岛和东塔斯曼高原的古温标比较表明，在相似的古纬度上，这两个地点之间存在一个大而一致的始新世中晚期海温梯度，约为7℃。中等复杂气候模式模拟表明，罗斯海深水形成驱动的南太平洋海洋热输送增强是观测到的海温梯度的主要原因。这些结果表明，超过18℃的非常温暖的海温在始新世南部高纬度地区并没有均匀地延伸，并表明温盐环流可能部分控制了温室气候下高纬度海洋温度的分布。始新世海温明显的纬向非均质性提醒我们，在给定的纬向带内使用空间有限的数据来推断过去的经向温度梯度。
Paleoclimate studies suggest that increased global warmth during the Eocene epoch was greatly amplified at high latitudes, a state that climate models cannot fully reproduce. However, proxy estimates of Eocene near-Antarctic sea surface temperatures (SSTs) have produced widely divergent results at similar latitudes, with SSTs above 20 degrees C in the southwest Pacific contrasting with SSTs between 5 and 15 degrees C in the South Atlantic. Validation of this zonal temperature difference has been impeded by uncertainties inherent to the individual paleotemperature proxies applied at these sites. Here, we present multiproxy data from Seymour Island, near the Antarctic Peninsula, that provides well-constrained evidence for annual SSTs of 10-17 degrees C (1 sigma SD) during the middle and late Eocene. Comparison of the same paleotemperature proxy at Seymour Island and at the East Tasman Plateau indicate the presence of a large and consistent middle-to-late Eocene SST gradient of similar to 7 degrees C between these two sites located at similar paleolatitudes. Intermediate-complexity climate model simulations suggest that enhanced oceanic heat transport in the South Pacific, driven by deep-water formation in the Ross Sea, was largely responsible for the observed SST gradient. These results indicate that very warm SSTs, in excess of 18 degrees C, did not extend uniformly across the Eocene southern high latitudes, and suggest that thermohaline circulation may partially control the distribution of high-latitude ocean temperatures in greenhouse climates. The pronounced zonal SST heterogeneity evident in the Eocene cautions against inferring past meridional temperature gradients using spatially limited data within given latitudinal bands.