Paleoceanography of the Southeast Pacific since the late glacial from diatom and foraminiferal assemblages

IF 2.6 2区 地球科学 Q2 GEOGRAPHY, PHYSICAL
Elisabeth Teca Oliva , Elisabeth Michel , Giuseppe Siani , Xavier Crosta , Carina B. Lange , Consuelo Martínez Fontaine , Paola Cárdenas
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引用次数: 0

Abstract

The Southern Ocean is a key region for climate changes, notably for deep ocean–atmosphere CO2 exchange, linked to the upwelling of deep waters, south to the Polar Front, that is driven through Southern Hemisphere Westerly Winds and Antarctic Circumpolar Current positions and intensities. Previous studies using a range of different proxies have proposed the latitudinal migration of the Antarctic Circumpolar Current and Southern Westerly Winds in the Southeast Pacific since the Last Glacial Maximum, but with conflicting results. We present a paleoceanographic reconstruction from the Last Glacial period to the Late Holocene based on diatom and foraminiferal assemblages from the marine sediment core MD07-3081, retrieved from the Southeast Pacific at 49° S, proximal (∼100 km) offshore the south coast of Chile. During the Last Glacial, the presence of polar diatoms is not observed, suggesting that the Polar Front did not approach 49° S. During the deglaciation, an increase of Chaetoceros spp. spores is observed together with the opportunistic planktonic foraminifer Globigerinita glutinata, which indicates a greater nutrient availability, linked to the influence of the Southern Ocean upwelling. The presence of Neogloboquadrina incompta, a subtropical species, during two periods of the deglaciation (15.2 ka and 12.3–11.5 ka) is associated with a southward shift of the Subtropical Front linked to a reduction of the South Pacific split jet. During the deglaciation to the Early Holocene transition, the increase of open ocean diatoms thriving both north and south of the Subantarctic Zone indicates a greater influence of the Antarctic Circumpolar Current, possibly displaced ∼3° south of its current position at 46° S. In the Late Holocene, the increase of subtropical-temperate species, e.g. Fragilariopsis doliolus, is indicative of a greater influence of warm waters coming from the Peru–Chile Countercurrent. This study of the diatom and foraminiferal assemblages provide new insights into the paleoceanography of the SE Pacific since the Last Glacial Maximum and the role of the Southern Ocean during this climate transition.
从硅藻和有孔虫组合看冰川晚期以来的东南太平洋古海洋学
南大洋是气候变化的关键区域,特别是深海-大气二氧化碳交换的关键区域,这与南至极地前沿的深海水域上涌有关,而南半球西风和南极环极洋流的位置和强度则是推动这种上涌的因素。以前的研究使用了一系列不同的代用指标,提出了自末次冰川极盛时期以来南极环极洋流和南半球西风在东南太平洋的纬度迁移,但结果相互矛盾。我们根据从南纬 49°、智利南海岸近海(∼100 千米)的东南太平洋海洋沉积物岩芯 MD07-3081 中提取的硅藻和有孔虫组合,重建了从末次冰期到全新世晚期的古海洋学。在末次冰期,没有观察到极地硅藻的存在,这表明极地前线没有接近南纬 49 度。在脱冰期,观察到 Chaetoceros 属孢子和机会性浮游有孔虫 Globigerinita glutinata 的增加,这表明与南大洋上升流的影响有关,营养物质的供应增加了。在两个降冰期(15.2 ka ka 和 12.3-11.5 ka)出现了亚热带物种 Neogloboquadrina incompta,这与南太平洋分裂喷流减弱导致的亚热带前线南移有关。在脱冰期向全新世早期过渡期间,亚南极区以北和以南的开阔洋硅藻增多,表明南极环极洋流的影响增大,可能从其目前的南纬 46°位置向南移动了 3°。在全新世晚期,亚热带-温带物种(如 Fragilariopsis doliolus)增多,表明来自秘鲁-智利逆流的暖流的影响增大。这项硅藻和有孔虫组合研究为了解末次冰川极盛时期以来东南太平洋的古海洋学以及南大洋在这一气候转变过程中的作用提供了新的视角。
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来源期刊
CiteScore
5.90
自引率
10.00%
发文量
398
审稿时长
3.8 months
期刊介绍: Palaeogeography, Palaeoclimatology, Palaeoecology is an international medium for the publication of high quality and multidisciplinary, original studies and comprehensive reviews in the field of palaeo-environmental geology. The journal aims at bringing together data with global implications from research in the many different disciplines involved in palaeo-environmental investigations. By cutting across the boundaries of established sciences, it provides an interdisciplinary forum where issues of general interest can be discussed.
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