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首页> 外文期刊>Paleoceanography >Millennial variability and long-term changes of the diatom production in the eastern equatorial Pacific during the last glacial cycle
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Millennial variability and long-term changes of the diatom production in the eastern equatorial Pacific during the last glacial cycle

机译：上一个冰川周期，赤道东太平洋硅藻产量的千年变化和长期变化

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The modern eastern equatorial Pacific (EEP) is a major natural source for atmospheric carbon dioxide and is thought to be connected to high-latitude ocean dynamics by oceanic teleconnections on glacial-interglacial timescales. A wealth of sedimentary records aiming at reconstructing last Quaternary changes in primary productivity and nutrient utilization have been devoted to understanding those linkages between the EEP and other distant oceanic areas. Most of these records are, however, clustered in the pelagic EEP cold tongue, with comparatively little attention devoted to coastal areas. Here we present downcore measurements of the composition and concentration of the diatom assemblage together with opal (biogenic silica) concentration at site MD02-2529 recovered in the coastal Panama Basin. Piston core MD02-2529, collected in an area affected by a multitude of processes, provides evidence for strong variations in diatom production at the millennial timescale during the last glacial cycle. The maxima in total diatom concentration occurred during the early marine isotopic stage (MIS) 4 as well as during the MIS 4/3 transition and MIS 3. Rapid changes in diatom concentrations during the MIS 3 mimics Bond cycles as independently recorded by the sea surface salinity estimation derived from planktonic foraminifera from the same core. Such patterns indicate a clear linkage between diatom production in the coastal EEP and rapid climate changes in the high-latitude North Atlantic. In parallel, the long-term succession of the diatom community from coastal diatoms, predominantly thriving during MIS 5 and 4, toward pelagic diatoms, dominant during MIS 3 and 2, points to a long-term change in the surface hydrology. During Heinrich events, diatoms strongly reduced their production, probably because of enhanced stratification in the upper water column. After the last glacial maximum, diatom production and valve preservation strongly decreased in response to the advection of nutrient-depleted (H_2SiO_4), warmer water masses. Our high-resolution record highlights how regional climatic processes can modulate rapid changes in siliceous primary production as triggered by wind-induced local upwelling, indicating that millennial climatic variability can overtake other prominent hydrological processes such as those related to silicic acid leakage.
机译：现代的赤道东太平洋（EEP）是大气中二氧化碳的主要自然来源，据认为可以通过冰川间时间尺度上的海洋遥相关与高纬度海洋动力学联系起来。大量的沉积记录旨在重建初级生产力和养分利用的最后第四纪变化，已专门用于了解EEP与其他远洋区域之间的联系。但是，这些记录大多数都集中在中上层EEP冷舌上，而对沿海地区的关注相对较少。在这里，我们介绍了在巴拿马海岸沿海地区回收的MD02-2529站点上硅藻组合物的组成和浓度以及蛋白石（生物硅）浓度的下限测量值。活塞芯MD02-2529收集在受多个过程影响的区域中，这为在上个冰川周期的千年时间尺度上硅藻产量的巨大变化提供了证据。总硅藻浓度的最大值发生在早期海洋同位素阶段（MIS）4以及MIS 4/3过渡和MIS 3期间。硅藻浓度的快速变化模仿了MIS 3的键合周期，这是由海面独立记录的来自同一岩心的浮游有孔虫的盐度估算。这种模式表明沿海EEP的硅藻产量与高纬度北大西洋的快速气候变化之间存在明确的联系。同时，硅藻群落从沿海硅藻的长期演替，主要是在MIS 5和MIS 4期间蓬勃发展，而上层硅藻则在MIS 3和MIS 2期间占主导地位，这表明了地表水文学的长期变化。在海因里希（Heinrich）事件中，硅藻极大地降低了其产量，这可能是由于上部水柱中的分层增加所致。在最后一次冰川期之后，硅藻的产生和瓣膜的保存随着营养物质耗尽（H_2SiO_4）和较暖水团的平流而大大降低。我们的高分辨率记录突显了区域性气候过程如何调节由风引起的局部上升流触发的硅质初级生产的快速变化，这表明千禧年的气候变化可以超过其他重要的水文过程，例如与硅酸泄漏有关的过程。

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