Paleonutrient and productivity records from the subarctic North Pacific
Paleonutrient and productivity records from the subarctic North Pacific
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DOI：
10.1594/pangaea.701578
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发表时间：
2008-08
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影响因子：
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通讯作者：
H. Gebhardt;M. Sarnthein;P. Grootes;T. Kiefer;Hartmut Kühn;F. Schmieder;U. Röhl
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文献类型：
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作者：
H. Gebhardt;M. Sarnthein;P. Grootes;T. Kiefer;Hartmut Kühn;F. Schmieder;U. Röhl
我们的研究解决了亚北极北太平洋经向翻转环流（MOC）轨道和千年尺度变化的模式和时间的基本问题。特别值得关注的是垂直混合、尽管存在强烈分层但地表水中当前和过去丰富的营养物质，以及北太平洋-北大西洋海面温度（SST）振荡的跷跷板。为此，我们生成并解释了沿着两个长活塞核心（各一个来自亚北极太平洋西部和东部）的冰川终止 I-V 的多个记录。二氢卟酚和生物蛋白石是地表水生产力的代表；底栖有孔虫的δ(13)C是深水通气的记录；和厚皮猪笼草的 delta(13)C。是地下水中营养物的示踪剂，在垂直混合期间延伸到海面。混合程度通过配对浮游表面和地下（密斜层）居民的海温和 delta(18)O 记录来追踪。严格的年龄控制是从终端 I 和海底三角洲 (18)O 的一系列年龄校准的 (14)C 高原边界以及过去 800 ka 的地磁事件中推断出来的。碳 14 古储层年龄记录了地表和深水的年龄，以揭示终端 I 期间 MOC 的短期变化。我们为终端 I 定义了短期生产力事件的标准序列，在过去 450 ka 的终端 II 至 V 以及随后的间冰期期间也很明显。稳定层化和低生产力的冰川峰值状态在接近 17ka 时终止，同时冰漂流和融化也结束，类似于终止 I 开始后的 2000 年。随后出现了来自亚热带的垂直混合和温暖地表水的入侵。对流的年轻水团最终在17.0至小于14.5ka时渗透到3600米水深，显着改善了晚冰消期和最早间冰期的底层水通气。与来自密丽斜层的上升养分混合，分别在 17-15 ka 和 15-12 ka 附近诱导藻类二氢卟酚和生物蛋白石产量的短期最大值。 15.5ka之后，阿留申洋流的冰消融水入侵和来自北美河流的二氧化硅输入也促进了东太平洋的生产力。在冰消期晚期和间冰期早期，生产力下降，同时期，由于低有机通量和通风良好的深水，CaCO(3) 保存出现异常高峰。随后，低盐度和凉爽的表层水逐渐恢复，层化又逐渐恢复。第二个以蛋白石为主的生产力最高点标志着间冰期的结束。 17-11ka左右的冰消期垂直混合脉冲意味着北太平洋对海洋CO(2)同时释放到大气中的重要贡献，并支持气候变化的东西向跷跷板模型。
Our study addresses fundamental questions of the mode and timing of orbital and millennial-scale changes in the meridional overturning circulation (MOC) of the subarctic North Pacific. Particular concerns are the vertical mixing, the present and past abundance of nutrients in surface waters despite strong stratification, and the North Pacific-North Atlantic seesaw of oscillations in sea surface temperature (SST). We do this by generating and interpreting multiple records for glacial terminations I-V down two long piston cores, one each from the western and eastern subarctic Pacific. Chlorins and biogenic opal are proxies for surface water productivity; delta(13)C of epibenthic foraminifera is a record of deepwater ventilation; and the delta(13)C of N. pachyderma sin. is a tracer of nutrients in subsurface waters that extend up to the sea surface during times of vertical mixing. The degree of mixing is traced by pairing SST and delta(18)O records of planktic surface and subsurface (pycnocline) dwellers. Tight age control is deduced from a suite of age-calibrated (14)C plateau boundaries for Termination I and benthic delta(18)O and geomagnetic events for the last 800 ka. Carbon 14 paleoreservoir ages record the ages of surface and deep waters to uncover short-term changes in MOC over Termination I. We have defined a standard sequence of short-term productivity events for Termination I, also evident during terminations II to V and subsequent interglacials over the last 450 ka. The peak glacial regime of stable stratification and low productivity terminated, together with the end of ice rafting and melting, near 17 ka, similar to 2000 years after the onset of Termination I. Pulses of vertical mixing and incursion of warm surface waters from the subtropics followed. Convected young water masses finally penetrated down to 3600-m water depth at 17.0 to less than 14.5 ka, significantly improving bottom water ventilation through the late deglacial and earliest interglacial. Mixing with upwelled nutrients from the pycnocline induced short-term maxima in algal production of chlorins and biogenic opal near 17-15 and 15-12 ka, respectively. Deglacial meltwater incursions in the Aleutian Current and silica input from North American rivers also promoted East Pacific productivity after 15.5 ka. Productivity decreased during the late deglacial and early interglacial, coeval with an exceptional peak in CaCO(3) preservation caused by both low organic flux and well-ventilated deepwater. Subsequently, low salinity and cool surface waters and in turn, stratification were gradually restored. A second, opal-dominated productivity maximum marked the ends of interglacials. The deglacial pulses of vertical mixing around 17-11 ka imply an important contribution of the North Pacific to the coeval release of oceanic CO(2) into the atmosphere and support the east-west seesaw model of climate change.