Late Cretaceous seasonal ocean variability from the Arctic
Late Cretaceous seasonal ocean variability from the Arctic
复制标题
DOI：
10.1038/nature08141
复制
发表时间：
2009-07-09
期刊：
影响因子：
64.8
通讯作者：
Pike, Jennifer
中科院分区：
文献类型：
--
作者：
Davies, Andrew;Kemp, Alan E. S.;Pike, Jennifer
现代北冰洋被认为是全球变化的晴雨表和全球变暖的放大器（1），因此过去北极变化的记录对古气候重建至关重要。人们对晚白垩世温室期（6500 - 9900万年前）北冰洋的状况知之甚少，但这些时期的记录可能会为北冰洋在不久的将来温暖气候中的行为提供重要线索。在这里，我们提出了一个季节性解决白垩纪沉积记录从阿尔法海岭的北冰洋。这一古沉积物圈闭为白垩纪海洋生物碳泵的运作提供了新的见解。季节性初级生产主要由硅藻藻类，但与先前假设的上升流无关（2）。相反，生产发生在一个分层的水柱中，涉及特别适应的物种，其开花类似于现代北太平洋亚热带环流（3）或地中海腐泥（4）。随着CO2水平的增加和变暖目前正在推动全球海洋分层的增加（5），这种适应分层的生产方式可能会变得更加普遍。我们关于季节性硅藻生产和通量的证据证明夏季无冰，但硅藻软泥中陆源沉积物的薄堆积与冬季间歇性海冰的存在相一致，支持晚白垩世北冰洋低温的广泛证据（6-8），而不是最近提出的15摄氏度的年平均温度。
The modern Arctic Ocean is regarded as a barometer of global change and amplifier of global warming(1) and therefore records of past Arctic change are critical for palaeoclimate reconstruction. Little is known of the state of the Arctic Ocean in the greenhouse period of the Late Cretaceous epoch (65-99 million years ago), yet records from such times may yield important clues to Arctic Ocean behaviour in near-future warmer climates. Here we present a seasonally resolved Cretaceous sedimentary record from the Alpha ridge of the Arctic Ocean. This palaeo-sediment trap provides new insight into the workings of the Cretaceous marine biological carbon pump. Seasonal primary production was dominated by diatom algae but was not related to upwelling as was previously hypothesized(2). Rather, production occurred within a stratified water column, involving specially adapted species in blooms resembling those of the modern North Pacific subtropical gyre(3), or those indicated for the Mediterranean sapropels(4). With increased CO2 levels and warming currently driving increased stratification in the global ocean(5), this style of production that is adapted to stratification may become more widespread. Our evidence for seasonal diatom production and flux testify to an ice-free summer, but thin accumulations of terrigenous sediment within the diatom ooze are consistent with the presence of intermittent sea ice in the winter, supporting a wide body of evidence for low temperatures in the Late Cretaceous Arctic Ocean(6-8), rather than recent suggestions of a 15 degrees C mean annual temperature at this time(9).