Benthic foraminifera indicate Glacial North Pacific Intermediate Water and reduced primary productivity over Bowers Ridge, Bering Sea, since the Mid-Brunhes Transition
Benthic foraminifera indicate Glacial North Pacific Intermediate Water and reduced primary productivity over Bowers Ridge, Bering Sea, since the Mid-Brunhes Transition
复制标题
DOI：
10.5194/jm-38-177-2019
复制
发表时间：
2019-12
影响因子：
2
通讯作者：
S. Kender;A. Aturamu;J. Zalasiewicz;M. Kaminski;M. Williams
中科院分区：
文献类型：
--
作者：
S. Kender;A. Aturamu;J. Zalasiewicz;M. Kaminski;M. Williams
抽象。从大约400 ka开始，中布鲁赫过渡期（MBT）的冰芯和深海记录中表达的冰川周期幅度增加，但其对高纬度气候的影响尚未完全了解。北冰洋被认为已经变暖，海冰减少，但对白令海等海冰边缘地区知之甚少。白令海是北极和太平洋之间的联系，是一个高生产力和二氧化碳通风的地区;它拥有一个明显的氧气最小区（OMZ），被认为是更新世冰川北太平洋中层水（GNPIW）形成的位置。为了了解该地区的古海洋学变化，我们分析了过去600 kyr Bowers Ridge（地点U1342，水深800 m）的底栖有孔虫动物群，因为它们保存完好，对深海和表层海洋条件的变化非常敏感。我们确定和成像71类群，并提供了一个完整的分类。有孔虫保存在冰川期明显较高，表明存在腐蚀性较小的GNPIW。最丰富的物种是Bulimina exilis、Takayanagia delicata、Escheraminella weddellensis、Gyroidina sp. 2、Cassidulina laevigata、Islandiella norcrossi和Uvigerina bifurcata，这与过去60万年来广泛的高净初级生产力相一致。对应分析表明，最重要的组合1包括B。exilis，T. delicata、Boliosspissa和Brizalina，这些化石零星地出现在富含生物的层状沉积物的间隔内，大多发生在冰川期，也有一些发生在冰消期，被解释为表明生产力非常高。其他组合包括植食性物种A。威德伦西斯岛norcrossi和C. laevigata，指示季节性浮游植物水华。在MBT之前，非常高产的组合1和A的更多层段。weddellensis发生，我们认为这反映了更多的海冰相关的季节性分层和冰缘水华的时间。我们的推断减少海冰融水分层的影响，在白令海中部的MBT后是一致的记录表明，北极和太平洋在冰川期间变暖，并表明高纬度的生产力和海冰变化是这个气候事件的一个重要特征。
Abstract. The Mid-Brunhes Transition (MBT) saw an increase in the amplitude of glacial cycles expressed in ice core and deep ocean records from about 400 ka, but its influence on high-latitude climates is not fully understood. The Arctic Ocean is thought to have warmed and exhibited reduced sea ice, but little is known of sea ice marginal locations such as the Bering Sea. The Bering Sea is the link between the Arctic and Pacific Ocean and is an area of high productivity and CO2 ventilation; it hosts a pronounced oxygen minimum zone (OMZ) and is thought to be the location of Glacial North Pacific Intermediate Water (GNPIW) formation in the Pleistocene. To understand palaeoceanographic change in the region, we analysed benthic foraminiferal faunas from Bowers Ridge (Site U1342, 800 m of water depth) over the past 600 kyr, as they are uniquely well preserved and sensitive to changes in deep and surface ocean conditions. We identified and imaged 71 taxa and provide a full taxonomy. Foraminiferal preservation is markedly higher during glacials, indicating the presence of less corrosive GNPIW. The most abundant species are Bulimina exilis, Takayanagia delicata, Alabaminella weddellensis, Gyroidina sp. 2, Cassidulina laevigata, Islandiella norcrossi, and Uvigerina bifurcata, consistent with broadly high net primary production throughout the last 600 kyr. Correspondence analysis shows that the most significant Assemblage 1 comprises B. exilis, T. delicata, Bolivina spissa, and Brizalina, which occur sporadically within intervals of laminated, biogenic-rich sediment, mostly during glacials and also some deglacials, and are interpreted as indicating very high productivity. Other assemblages contain the phytodetritivore species A. weddellensis, I. norcrossi, and C. laevigata, indicative of seasonal phytoplankton blooms. Before the MBT, more numerous intervals of the very high-productivity Assemblage 1 and A. weddellensis occur, which we suggest reflect a time of more sea-ice-related seasonal stratification and ice edge blooms. Our inference of a decrease in sea ice meltwater stratification influence in the central Bering Sea after the MBT is consistent with records showing that the Arctic and Pacific Ocean warmed during glacials and suggests that high-latitude productivity and sea ice changes were an important feature of this climate event.