Paleoceanography最新文献_第5页

Influence of ocean tides on the general ocean circulation in the early Eocene 始新世早期海潮对海洋环流的影响

Paleoceanography

Pub Date : 2017-06-01 DOI: 10.1002/2016PA002997

T. Weber, Maik Thomas

The early Eocene (∼56-50 million years ago) was characterized by higher surface temperatures and a reduced meridional temperature gradient, compared to present-day conditions. The origin of the decreased meridional temperature gradient is still subject to discussion and might be linked to tides. Tidal mixing could have enhanced the meridional heat transport and thereby decreased the meridional temperature gradient. We test this hypothesis by simultaneously modelling tidal dynamics and the general ocean circulation for the early Eocene in a new coupled atmosphere-ocean model setup. We find an interaction between tidal currents and the ocean general circulation that increases horizontal velocities in 25% of the deep ocean to more than 400% of its original value. The global meridional overturning circulation (GMOC) is strengthened thereby locally by 60-100%. However, the oceanic meridional heat transport is only increased by a maximum of 0.1PW (8%) and a mean of less than 0.018PW (5.1%), thus not decreasing the meridional temperature gradient considerably.

始新世早期(约5600 - 5000万年前)的特征是与现在的条件相比，地表温度较高，经向温度梯度减小。经向温度梯度减小的原因仍有待讨论，可能与潮汐有关。潮汐混合可能增强了经向热输运，从而降低了经向温度梯度。我们通过在一个新的大气-海洋耦合模式设置中同时模拟始新世早期的潮汐动力学和一般海洋环流来验证这一假设。我们发现潮流和海洋环流之间的相互作用使25%的深海水平速度增加到其原始值的400%以上。全球经向翻转环流(GMOC)因此在局部加强了60-100%。而海洋经向热输运最大增幅仅为0.1PW(8%)，平均增幅小于0.018PW(5.1%)，并未显著降低经向温度梯度。

引用次数: 11

New evidence for Kuroshio inflow and deepwater circulation in the Okinawa Trough, East China Sea: Sedimentary mercury variations over the last 20 kyr 东海冲绳海槽黑潮流入和深水环流的新证据：过去20 kyr的沉积汞变化

Paleoceanography

Pub Date : 2017-06-01 DOI: 10.1002/2017PA003116

D. Lim, Jihun Kim, Zhaokai Xu, K. Jeong, H. Jung

The evolution of the Kuroshio Current (KC) in the Okinawa Trough (OT) has long been of paleoceanographic interest and has been the focus of many investigations because of its large impacts on both the ocean environment and the climate in East Asia. Here, we present a new high-resolution mercury (Hg) record from the OT sediments that provides robust evidence for the glacial-interglacial variabilities of KC inflow. The Hg levels are anomalously high in the Holocene deposits, which feature a large and abrupt Hg increase at ~9.6 ka and a significant drop at 4.5–3.2 ka. Our observations show that most Hg was derived from seafloor hydrothermal plumes via active lateral transportation. Thus, the generally high Hg levels since ~9.6 ka are associated with enhanced basin-wide deep-water circulation triggered by the KC inflow. This driving mechanism for the deposition and widespread of Hg is also evidenced by an abrupt drop in Hg levels during the late Holocene neoglacial cold period (~5–3 ka) when the KC inflow was temporarily interrupted and deep-water circulation was consequently weak or even absent in the OT. The changes in sedimentary Hg appear to be synchronous with those in other geochemical proxies that suggest that bottom water conditions switched from anoxic to oxic due to increased upwelling from the bottom in tandem with the strengthening KC and reduced freshwater effect since ~9.6 ka. This study shows that the hydrothermal Hg is a sensitive and independent tool for the reconstruction of palaeo-dynamics of KC in the OT.

冲绳海槽黑潮(Kuroshio Current, KC)的演变对东亚海洋环境和气候的影响很大，一直是古海洋学研究的焦点。在此，我们提出了一种新的高分辨率汞(Hg)记录，为KC流入的冰期-间冰期变化提供了有力的证据。全新世沉积物中汞含量异常高，在~9.6 ka时汞含量急剧上升，在4.5 ~ 3.2 ka时汞含量显著下降。我们的观测结果表明，大部分汞来自海底热液柱，通过积极的横向运输。因此，自~9.6 ka以来，汞含量普遍偏高与KC流入引发的全流域深水环流增强有关。全新世晚期新冰期寒冷期(~5 ~ 3ka)汞含量的骤降也证明了汞的沉积和广泛分布的驱动机制，当时KC流入暂时中断，深水环流因此减弱甚至没有。沉积汞含量的变化与其他地球化学指标的变化基本一致，表明~9.6 ka以来，随着KC的增强和淡水效应的减弱，海底上升流的增加导致了底水条件由缺氧向缺氧的转变。研究表明，热液汞是重建第三系KC古动力学的一个敏感而独立的工具。

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引用次数: 42

Closing an early Miocene astronomical gap with Southern Ocean δ18O and δ13C records: Implications for sea level change 用南大洋δ18O和δ13C记录缩小中新世早期的天文差距：对海平面变化的影响

Paleoceanography

Pub Date : 2017-06-01 DOI: 10.1002/2016PA003074

K. Miller, Ronidell Baluyot, J. Wright, R. Kopp, J. Browning

We present orbital-scale resolution (~10-kyr) benthic foraminiferal δ18O and δ13C records from the Kerguelen Plateau (Ocean Drilling Program [ODP] Sites 751 and 747) from 14.5-20.0 Ma spanning the Miocene climate optimum (MCO; 15-17 Ma). Our records fill a critical gap from ~17-18 Ma, a time when many other deep-sea records are affected by dissolution. We tested the fidelity of published magneto-biostratigraphic age models for these sites by astronomically tuning to the 405-kyr eccentricity cycle. A comparison of spectral estimates between the untuned and tuned records, as well as coherency with Laskar's (2004) eccentricity solution, revealed quasi-100-kyr cyclicity in δ18O and δ13C. There is only a weak signal associated with the 41-kyr obliquity cycle, likely due to the 10-kyr sampling limiting resolution. The δ18O variations point to persistent 405- and quasi-100-kyr modulations of temperature and sea-level changes through the early to middle Miocene as predicted by astronomical solutions, with changing dominance of the 100- and 41-kyr beat. Comparison of δ18O records with early to middle Miocene sequences from the New Jersey shelf, northeast Australian margin, Bahamas, and Maldives suggests that the dominant sea-level period preserved is the 1.2-Myr obliquity cycle, with sequence boundaries associated with δ18O increases or maxima. On the New Jersey margin, higher order sequences reflect the quasi-100-kyr eccentricity cycles as modulated by 405-kyr cycles. We suggest that “nesting” of stratigraphic cycles is a function of: 1) pervasive (though changing) Milankovitch forcing of global mean sea-level change; and 2) preservation that depends on sufficient sediment supply and accommodation.

本文给出了来自克格伦高原(Ocean Drilling Program [ODP] Sites 751 and 747) 14.5-20.0 Ma的轨道尺度分辨率(~10-kyr)底栖有孔虫δ18O和δ13C记录，跨越中新世气候最佳(MCO;15 - 17日)。我们的记录填补了~17-18 Ma的关键空白，这一时期许多其他深海记录受到溶解作用的影响。我们通过天文校正到405 kyr的离心旋回，测试了这些地点已发表的磁生物地层年龄模型的保真度。通过比较非调谐和调谐记录之间的光谱估计，以及与Laskar(2004)的偏心率解的一致性，揭示了δ18O和δ13C的准100 kyr周期。只有一个微弱的信号与41kyr的倾角周期有关，可能是由于10kyr的采样限制分辨率。δ18O的变化表明，在早至中新世中期，温度和海平面变化持续存在405-和准100-kyr的调制，其中100-和41-kyr的调制占主导地位。与新泽西陆架、澳大利亚东北缘、巴哈马和马尔代夫早中新世至中中新世层序的δ18O记录比较表明，保留的主要海平面期为1.2 myr倾角旋回，层序边界与δ18O增加或最大值有关。在新泽西边缘，高阶层序反映了经过405-kyr旋回调制的准100-kyr偏心旋回。我们认为地层旋回的“嵌套”是以下因素的函数:1)全球平均海平面变化的普遍(尽管在变化)米兰科维奇强迫;2)保存取决于足够的沉积物供应和容纳。

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引用次数: 20

Precessional variability of 87 Sr/86 Sr in the late Miocene Sorbas Basin: An interdisciplinary study of drivers of interbasin exchange 中新世晚期Sorbas盆地87Sr/86Sr的专业前变异性：跨流域交换驱动因素的跨学科研究

Paleoceanography

Pub Date : 2017-06-01 DOI: 10.1002/2016PA003061

S. Modestou, D. Simon, M. Gutjahr, A. Marzocchi, T. Kouwenhoven, R. Ellam, R. Flecker

We present the first subprecessional record of seawater 87Sr/86Sr isotope ratios for a marginal Mediterranean subbasin. The sediments contained in this interval (three precessional cycles between 6.60 and 6.55 Ma) are important because they record conditions during the transition to the Messinian Salinity Crisis (MSC; 5.97 to 5.33 Ma), an event for which many details are still poorly understood. The record, derived from planktic foraminifera of the late Miocene Sorbas Basin (SE Spain), shows brief excursions with precessional cyclicity to 87Sr/86Sr ratios higher than coeval ocean 87Sr/86Sr. The hydrologic conditions required to generate the observed record are investigated using box modeling, constrained using a new paleodepth estimate (150 to 250 m) based on benthic foraminiferal assemblages. The box model results highlight the role of climate-driven interbasin density contrast as a significant driver of, or impediment to, exchange. The results are particularly significant in the context of the MSC, where 87Sr/86Sr excursions have been interpreted purely as a consequence of physical restriction. To replicate the observed temporal patterns of lithological variations and 87Sr/86Sr isotope excursions, the Sorbas Basin “box” must have a mainly positive hydrologic budget, in contrast with the Mediterranean's negative budget during the late Miocene. This result has implications for the assumption of synchronous deposition of specific sedimentary layers (sapropels) between marginal and open Mediterranean settings at subprecessional resolution. A net positive hydrologic budget in marginal Mediterranean subbasins may reconcile observations of freshwater inclusions in gypsum deposits.

本文首次记录了地中海边缘次海盆海水87Sr/86Sr同位素比值的次进动记录。这段时间(6.60 ~ 6.55 Ma的三个旋进周期)的沉积物非常重要，因为它们记录了向墨西尼亚盐度危机(MSC;5.97至5.33 Ma)，该事件的许多细节仍不清楚。来自晚中新世Sorbas盆地(西班牙东南部)浮游有孔虫的记录显示，与同期海洋87Sr/86Sr相比，87Sr/86Sr的岁差旋回率出现了短暂的偏移。生成观测记录所需的水文条件使用盒模型进行了研究，约束条件是基于底栖有孔虫组合的新的古深度估计(150至250米)。箱形模式结果强调了气候驱动的流域间密度对比作为交换的重要驱动因素或障碍的作用。结果在MSC的背景下特别重要，其中87Sr/86Sr的漂移被解释为纯粹的物理限制的结果。为了复制观察到的岩性变化和87Sr/86Sr同位素漂移的时间模式，Sorbas盆地“盒子”必须具有主要的正水文收支，而地中海在晚中新世期间则为负水文收支。这一结果暗示了在亚进动分辨率下，边缘和开放地中海环境之间特定沉积层(岩石层)的同步沉积假设。地中海边缘次盆地的净正水文收支可能与石膏矿床中淡水包裹体的观测结果相符。

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引用次数: 16

Synchronous and proportional deglacial changes in Atlantic meridional overturning and northeast Brazilian precipitation 大西洋经向翻转和巴西东北部降水的同步和比例消融变化

Paleoceanography

Pub Date : 2017-06-01 DOI: 10.1002/2017PA003084

S. Mulitza, C. Chiessi, E. Schefuß, J. Lippold, David Wichmann, Benny Antz, A. Mackensen, A. Paul, M. Prange, K. Rehfeld, M. Werner, T. Bickert, N. Frank, H. Kuhnert, J. Lynch‐Stieglitz, R. Portilho-Ramos, A. Sawakuchi, M. Schulz, T. Schwenk, R. Tiedemann, M. Vahlenkamp, Yancheng Zhang

Changes in heat transport associated with fluctuations in the strength of the Atlantic meridional overturning circulation (AMOC) are widely considered to affect the position of the Intertropical Convergence Zone (ITCZ), but the temporal immediacy of this teleconnection has to date not been resolved. Based on a high resolution marine sediment sequence over the last deglaciation, we provide evidence for a synchronous and near-linear link between changes in the Atlantic interhemispheric sea surface temperature difference and continental precipitation over northeast Brazil. The tight coupling between AMOC strength, sea surface temperature difference and precipitation changes over northeast Brazil unambiguously points to a rapid and proportional adjustment of the ITCZ location to past changes in the Atlantic meridional heat transport.

与大西洋经向翻转环流(AMOC)强度波动相关的热输送变化被广泛认为会影响热带辐合带(ITCZ)的位置，但这种远相关的时间直接性迄今尚未得到解决。基于末次消冰期的高分辨率海洋沉积物序列，我们提供了大西洋半球海表温差变化与巴西东北部大陆降水之间的同步和近线性联系的证据。AMOC强度、海面温差和巴西东北部降水变化之间的紧密耦合，明确指出ITCZ位置对过去大西洋经向热输送变化的快速和比例调整。

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引用次数: 87

Calibration of the carbon isotope composition (δ13C) of benthic foraminifera 海底有孔虫碳同位素组成（δ13C）的校准

Paleoceanography

Pub Date : 2017-06-01 DOI: 10.1002/2016PA003072

A. Schmittner, H. Bostock, O. Cartapanis, W. Curry, H. Filipsson, E. Galbraith, J. Gottschalk, J. Herguera, B. Hoogakker, S. Jaccard, L. Lisiecki, D. Lund, G. Martínez﹣Méndez, J. Lynch‐Stieglitz, A. Mackensen, E. Michel, A. Mix, D. Oppo, C. Peterson, J. Repschläger, E. Sikes, H. Spero, C. Waelbroeck

The carbon isotope composition (δ13C) of seawater provides valuable insight on ocean circulation, air-sea exchange, the biological pump, and the global carbon cycle and is reflected by the δ13C of foraminifera tests. Here more than 1700 δ13C observations of the benthic foraminifera genus Cibicides from late Holocene sediments (δ13CCibnat) are compiled and compared with newly updated estimates of the natural (preindustrial) water column δ13C of dissolved inorganic carbon (δ13CDICnat) as part of the international Ocean Circulation and Carbon Cycling (OC3) project. Using selection criteria based on the spatial distance between samples, we find high correlation between δ13CCibnat and δ13CDICnat, confirming earlier work. Regression analyses indicate significant carbonate ion (−2.6 ± 0.4) × 10−3‰/(μmol kg−1) [CO32−] and pressure (−4.9 ± 1.7) × 10−5‰ m−1 (depth) effects, which we use to propose a new global calibration for predicting δ13CDICnat from δ13CCibnat. This calibration is shown to remove some systematic regional biases and decrease errors compared with the one-to-one relationship (δ13CDICnat = δ13CCibnat). However, these effects and the error reductions are relatively small, which suggests that most conclusions from previous studies using a one-to-one relationship remain robust. The remaining standard error of the regression is generally σ ≅ 0.25‰, with larger values found in the southeast Atlantic and Antarctic (σ ≅ 0.4‰) and for species other than Cibicides wuellerstorfi. Discussion of species effects and possible sources of the remaining errors may aid future attempts to improve the use of the benthic δ13C record.

海水的碳同位素组成（δ13C）为海洋环流、海气交换、生物泵和全球碳循环提供了有价值的见解，有孔虫测试的δ13C也反映了这一点。在这里，作为国际海洋循环和碳循环（OC3）项目的一部分，汇编了来自全新世晚期沉积物的1700多个海底有孔虫属Cibicide的δ13C观测值（δ13CCibnat），并与溶解无机碳的天然（前工业化）水柱δ13C的最新估计值进行了比较。使用基于样本之间空间距离的选择标准，我们发现δ13CCibnat和δ13CDICnat之间具有高度相关性，证实了早期的工作。回归分析表明，碳酸盐离子（−2.6±0.4）×10−3‰/（μmol kg−1。与一对一关系（δ13CDICnat=δ13CCibnat）相比，这种校准可以消除一些系统性的区域偏差并减少误差。然而，这些影响和误差减少相对较小，这表明以前使用一对一关系的研究得出的大多数结论仍然稳健。回归的剩余标准误差通常为σŞ0.25‰，在东南大西洋和南极发现的值更大（σŞ0.4‰），以及除乌埃勒斯托尔菲Cibicides以外的物种。对物种影响和剩余误差的可能来源的讨论可能有助于未来改进海底δ13C记录的使用。

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引用次数: 61

Mediterranean Outflow Water dynamics during the past ~570 kyr: Regional and global implications 过去~ 570kyr地中海流出水动态:区域和全球意义

Paleoceanography

Pub Date : 2017-06-01 DOI: 10.1002/2016PA003063

S. Kaboth, B. Boer, A. Bahr, C. Zeeden, L. Lourens

The Gulf of Cadiz constitutes a prime area to study teleconnections between the North Atlantic Ocean and climate change in the Mediterranean realm. In particular, the highly saline Mediterranean Outflow Water (MOW) is an important modulator of the North Atlantic salt budget on intermediate water levels. However, our understanding of its paleoceanographic evolution is poorly constrained due to the lack of high-resolution proxy records that predate the last glacial cycle. Here we present the first continuous and high-resolution (~ 1 kyr) benthic δ18O and δ13C as well as grain size records from Integrated Ocean Drilling Program Site U1386 representing the last ~570 kyr. We find three distinct phases of MOW variability throughout the Late to Middle Pleistocene at Site U1386 associated with prominent shifts in its composition and flow strength. We attribute this long-term variability to changes in water mass sourcing of the MOW. Superimposed on the long-term change in water mass sourcing is the occurrence of distinct and precession paced δ18O enrichment events, which contrast the pattern of global ice volume change as inferred from the global mean δ18O signal (i.e., LR04) but mimics that of the adjacent Mediterranean Sea. We attribute these enrichment events to a profound temperature reduction and salinity increases of the MOW, aligning with similar changes in the Mediterranean source region. These events might further signify ice volume increases as inferred from significant sea level drops recorded in the Red Sea and/or increased influence of North Atlantic intermediate water masses when MOW influence was absent at Site U1386.

加的斯湾是研究北大西洋与地中海地区气候变化之间遥相关关系的主要区域。特别是，地中海高盐流出水(MOW)是北大西洋中等水位盐收支的重要调节器。然而，由于缺乏在末次冰期之前的高分辨率替代记录，我们对其古海洋演化的理解受到了很好的限制。本文介绍了综合海洋钻探计划U1386站点第一次连续和高分辨率(~ 1 kyr)底栖生物δ18O和δ13C以及代表最后~570 kyr的粒度记录。我们发现U1386遗址在晚更新世至中更新世有三个不同的MOW变率阶段，其组成和流动强度发生了显著变化。我们将这种长期变率归因于MOW水团来源的变化。叠加在水团来源长期变化上的是明显的和以进动为节奏的δ18O富集事件，这与从全球平均δ18O信号(即LR04)推断的全球冰体积变化模式形成对比，但模仿了邻近地中海的变化模式。我们将这些富集事件归因于MOW的温度降低和盐度增加，这与地中海源区的类似变化一致。这些事件可能进一步表明，根据红海记录的显著海平面下降和/或在U1386站点没有MOW影响的情况下北大西洋中间水团的影响增加，冰量增加。

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引用次数: 24

Calibration of the B/Ca proxy in the planktic foraminifer Orbulina universa to Paleocene seawater conditions 浮游有孔虫(Orbulina universa)中B/Ca代用物与古新世海水条件的校正

Paleoceanography

Pub Date : 2017-06-01 DOI: 10.1002/2016PA003069

L. Haynes, B. Hönisch, K. Dyez, K. Holland, Y. Rosenthal, Carina R. Fish, A. Subhas, J. Rae

The B/Ca ratio of planktic foraminiferal calcite, a proxy for the surface ocean carbonate system, displays large negative excursions during the Paleocene-Eocene Thermal Maximum (PETM, 55.9 Ma), consistent with rapid ocean acidification at that time. However, the B/Ca excursion measured at the PETM exceeds a magnitude that modern pH calibrations can explain. Numerous other controls on the proxy have been suggested, including foraminiferal growth rate and the total concentration of dissolved inorganic carbon (DIC). Here we present new calibrations for B/Ca versus the combined effects of pH and DIC in the symbiont-bearing planktic foraminifer Orbulina universa, grown in culture solutions with simulated Paleocene seawater elemental composition (high [Ca], low [Mg], and low total boron concentration ([B]_T). We also investigate the isolated effects of low seawater [B]_T, high [Ca], reduced symbiont photosynthetic activity, and average shell growth rate on O. universa B/Ca in order to further understand the proxy systematics and to determine other possible influences on the PETM records. We find that average shell growth rate does not appear to determine B/Ca in high calcite saturation experiments. In addition, our “Paleocene” calibration shows higher sensitivity than the modern calibration at low [B(OH)_4−]/DIC. Given a large DIC pulse at the PETM, this amplification of the B/Ca response can more fully explain the PETM B/Ca excursion. However, further calibrations with other foraminifer species are needed to determine the range of foraminifer species-specific proxy sensitivities under these conditions for quantitative reconstruction of large carbon cycle perturbations.

浮游有孔虫方解石的B/Ca比是表层海洋碳酸盐系统的代表，在古新世-始新世热盛期（PETM，55.9 Ma）显示出较大的负偏移，与当时的快速海洋酸化一致。然而，在PETM测量的B/Ca偏移超过了现代pH校准可以解释的幅度。已经提出了对该代理的许多其他控制，包括有孔虫的生长速率和溶解无机碳（DIC）的总浓度。在这里，我们提出了B/Ca与pH和DIC共同作用的新校准，该共生体浮游有孔虫在模拟古新世海水元素组成（高[Ca]、低[Mg]和低总硼浓度（[B]_T）的培养溶液中生长。我们还研究了低海水[B]_T、高[Ca]、共生体光合活性降低和平均外壳生长速率对O.universa B/Ca的孤立影响，以进一步了解代理系统学并确定对PETM记录的其他可能影响。我们发现，在高方解石饱和度实验中，平均壳层生长速率似乎不能确定B/Ca。此外，我们的“古新世”校准在低[B（OH）_4−]/DIC下显示出比现代校准更高的灵敏度。给定PETM处的大DIC脉冲，B/Ca响应的这种放大可以更充分地解释PETM B/Ca偏移。然而，需要对其他有孔虫物种进行进一步的校准，以确定在这些条件下，有孔虫特定物种的代理灵敏度范围，从而定量重建大的碳循环扰动。

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引用次数: 28

Spatiotemporal variability in the δ¹⁸O-salinity relationship of seawater across the tropical Pacific Ocean. 热带太平洋海水δ 18o -盐度关系的时空变异。

Paleoceanography

Pub Date : 2017-05-13 DOI: 10.1002/2016PA003073

Jessica L Conroy, Diane M Thompson, Kim M Cobb, David Noone, Solanda Rea, Allegra N LeGrande

The relationship between salinity and the stable oxygen isotope ratio of seawater (δ¹⁸O_sw) is of utmost importance to the quantitative reconstruction of past changes in salinity from δ¹⁸O values of marine carbonates. This relationship is often considered to be uniform across water masses, but the constancy of the δ¹⁸O_sw-salinity relationship across space and time remains uncertain, as δ¹⁸O_sw responds to varying atmospheric vapor sources and pathways, while salinity does not. Here we present new δ¹⁸O_sw-salinity data from sites spanning the tropical Pacific Ocean. New data from Palau, Papua New Guinea, Kiritimati, and Galápagos show slopes ranging from 0.09 ‰/psu in the Galápagos to 0.32‰/psu in Palau. The slope of the δ¹⁸O_sw-salinity relationship is higher in the western tropical Pacific versus the eastern tropical Pacific in observations and in two isotope-enabled climate models. A comparison of δ¹⁸O_sw-salinity relationships derived from short-term spatial surveys and multi-year time series at Papua New Guinea and Galápagos suggests spatial relationships can be substituted for temporal relationships at these sites, at least within the time period of the investigation. However, the δ¹⁸O_sw-salinity relationship varied temporally at Palau, likely in response to water mass changes associated with interannual El Niño-Southern Oscillation (ENSO) variability, suggesting nonstationarity in this local δ¹⁸O_sw-salinity relationship. Applying local δ¹⁸O_sw-salinity relationships in a coral δ¹⁸O forward model shows that using a constant, basin-wide δ¹⁸O_sw-salinity slope can both overestimate and underestimate the contribution of δ¹⁸O_sw to carbonate δ¹⁸O variance at individual sites in the western tropical Pacific.

盐度与海水稳定氧同位素比值(δ18Osw)的关系对于通过海相碳酸盐δ18O值定量重建过去盐度变化具有重要意义。这种关系通常被认为是均匀的，但δ18Osw-盐度关系在空间和时间上的稳定性仍然是不确定的，因为δ18Osw响应不同的大气蒸汽源和途径，而盐度则没有。在这里，我们提供了来自热带太平洋站点的新δ 18osw -盐度数据。来自帕劳、巴布亚新几内亚、基里蒂玛蒂和Galápagos的新数据显示，Galápagos的坡度从0.09‰/psu到帕劳的0.32‰/psu不等。在观测和两种同位素气候模式中，热带西太平洋的δ 18osw -盐度关系斜率大于热带东太平洋。通过对巴布亚新几内亚和Galápagos的短期空间调查和多年时间序列得出的δ 18osw -盐度关系的比较表明，在这些地点，至少在调查的时间段内，空间关系可以代替时间关系。然而，帕劳的δ 18osw -盐度关系在时间上发生了变化，这可能是对年际El Niño-Southern涛动(ENSO)变率相关的水团变化的响应，表明该局部δ 18osw -盐度关系具有非平稳性。在珊瑚δ18O正演模型中应用局部δ18Osw-盐度关系表明，使用恒定的全盆地δ18Osw-盐度斜率可以高估和低估西热带太平洋个别地点δ18Osw对碳酸盐δ18O变化的贡献。

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引用次数: 34

The Holocene Labrador Current: Changing linkages to atmospheric and oceanographic forcing factors 全新世拉布拉多海流:与大气和海洋强迫因子的变化联系

Paleoceanography

Pub Date : 2017-05-01 DOI: 10.1002/2016PA003051

H. Rashid, D. Piper, K. Lazar, Kieran McDonald, F. Saint-Ange

The role of Labrador Current (LC) in providing freshwater to the North Atlantic and hence modulating the Atlantic meridional overturning circulation (AMOC) has been debated with very few data. This study provides the first data on the relative speed of the LC for the past 9.2 ka using mean size of the sortable silt of sediments as a proxy from a mid-shelf basin in the western Labrador Sea. LC speed progressively intensified from 9.2–5 ka, during which two meltwater events had minor influence. The LC was fastest between 5 ka and 3.1 ka and gradually weakened after 3.1 ka. The mean size of the sortable silt data shows overall co-variations with similar existing data from deep-water areas of the greater North Atlantic, suggesting an overarching link that modulates changes in both the near-surface and deep North Atlantic. A dynamical link between the LC and AMOC vigor is hypothesized in which high meltwater discharge in the Labrador Sea oriented the subpolar gyre (SPG) more North-South (meridional), weakening the SPG, and thus decelerating the upper limb of the AMOC. Conversely, reduction in LC transport during the late Holocene, due to the greater export of sea ice, oriented the SPG more East-West.

拉布拉多洋流（LC）在向北大西洋提供淡水从而调节大西洋经向翻转环流（AMOC）方面的作用一直存在争议，但数据很少。这项研究提供了过去9.2年LC相对速度的第一个数据 ka，使用拉布拉多海西部中陆架盆地沉积物的可分选淤泥的平均尺寸作为代理。LC速度从9.2–5逐渐增强 ka，期间两次融水事件影响较小。LC在5 ka和3.1 ka，3.1后逐渐减弱 ka。可分类淤泥数据的平均大小显示，与大北大西洋深水区的类似现有数据总体上存在协同变化，这表明一个总体联系调节了北大西洋近地表和深层的变化。假设LC和AMOC活力之间存在动力学联系，其中拉布拉多海的高融水排放使副极地环流（SPG）更加南北（经向），削弱了SPG，从而使AMOC的上肢减速。相反，由于海冰的大量出口，全新世晚期LC运输的减少使SPG更倾向于东西方。

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引用次数: 20