Millennial-scale changes of surface and bottom water conditions in the northwestern Pacific during the last deglaciation
Millennial-scale changes of surface and bottom water conditions in the northwestern Pacific during the last deglaciation
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DOI：
10.1016/j.gloplacha.2017.04.009
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发表时间：
2017-07
影响因子：
3.9
通讯作者：
Sunghan Kim;B. Khim;K. Ikehara;T. Itaki;A. Shibahara;Masanobu Yamamoto
中科院分区：
文献类型：
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作者：
Sunghan Kim;B. Khim;K. Ikehara;T. Itaki;A. Shibahara;Masanobu Yamamoto
利用地球化学、同位素指标和氧化还原元素组成，结合GH02-1030岩芯的烯酮海表温度（SST）和底栖有孔虫区系数据，重建了西北太平洋近23ka水柱条件的变化。以生物源蛋白石和TOC含量为主要代表的出口硅藻产量的地表水初级生产力与烯酮（春夏）海温和春夏混合层深度的发展密切相关。由体积δ15N和δ 30sidiatomn值估算的硝酸盐和硅酸利用的不同变化模式，很可能是由于水柱反硝化对体积δ15N的影响。b ølling- allero ød （BA）和Pre-Boreal （PB）期间出现了底水缺氧条件，表现为层状沉积物、丰富的底栖有孔虫和氧化还原元素组成的增加。虽然在BA和PB期间地表水生产力增加，但由于高纬度地区的融水输入，地表水生产力增加和北太平洋中间水（NPIW）通气减少共同导致了底水缺氧。根据西北太平洋、鄂霍次克海和白令海的GH02-1030岩心和其他岩心的记录，这些岩心都靠近现代NPIW源区，在BA时期，底部水溶解氧浓度比PB时期更耗尽。这种差异归因于BA期间比PB期间更多融水输入导致的NPIW通气更缓慢。白令海峡的开通或关闭对融水向西北太平洋运输的方向至关重要。
Changes in water column conditions in the northwestern Pacific during the last 23 ka were reconstructed using geochemical and isotope proxies and redox elemental compositions along with published data (alkenone sea surface temperature (SST) and benthic foraminiferal fauna) at core GH02-1030. Surface water primary productivity in terms of biogenic opal and TOC contents, which mainly represented export production of diatom, was closely related to alkenone (spring-summer) SST and the development of spring-summer mixed layer depth. The different variation patterns of nitrate and silicic acid utilization, estimated by bulk δ15N and δ30Sidiatomvalues, respectively, are most likely due to the water column denitrification influence on bulk δ15N. Dysoxic bottom water conditions occurred during the Bølling-Allerød (BA) and the Pre-Boreal (PB), which was evident by laminated sediments, abundant dysoxic benthic foraminifers, and increased redox elemental compositions. Although surface water productivity increased during the BA and PB, dysoxic bottom water conditions were caused by a combination of enhanced surface water productivity and reduced ventilation of North Pacific Intermediate Water (NPIW) in response to meltwater input from the high latitude areas. Based on records of core GH02-1030 and other cores in the northwestern Pacific, the Okhotsk Sea, and the Bering Sea, which are all proximal to the modern NPIW source region, dissolved oxygen concentrations of bottom water were more depleted during the BA than PB. Such difference was attributed to more sluggish NPIW ventilation due to more meltwater input during the BA than the PB. The opening or closure of the Bering Strait is critical to the direction of meltwater transport to the northwestern Pacific.