Collaborative Research: Evolution of Arctic Water Column Hydrography during the Holocene Based on a Novel Instrumentation Combination

合作研究：基于新型仪器组合的全新世北极水柱水文演化

• 批准号: 1550041
• 负责人: Reinhard Kozdon
• 金额: $ 26.71万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1550041&HistoricalAwards=false
• 关键词: Collaborative; Research; Evolution; Arctic; Water

During the past few decades, the Arctic has warmed approximately twice as rapidly as the entire northern hemisphere, associated with substantial retreat and thinning of the Arctic sea-ice cover during the past decade. Associated with the Arctic warming and waning sea-ice cover is a reorganization of the surface and deep-water circulation of the Arctic Ocean, but understanding of the associated processes is limited. The early to mid-Holocene provides a post-glacial analogue of a seasonally ice-free Arctic Ocean, similar to scenarios that have been proposed for the next several decades. This early-mid Holocene sea ice minimum, 10?6 thousand years ago, is often attributed to changes in solar forcing. However, records providing information on upper Arctic water column stratification during episodes of minimum sea ice cover are sparse. The normal paleoceanographic proxies for water mass stratification cannot be applied in the Arctic; different approaches are required to reconstruct water column hydrography. The proposed research has the potential to greatly improve our knowledge of past Arctic water column hydrography from the early to mid-Holocene sea ice minimum and inform scenario development of future conditions in the Arctic Ocean. The project will contribute to workforce development through support for the training of a PhD student. The technology developed will be proactively transferred to the international science community through a formal workshop. Recent innovations in the combined use of secondary ion mass spectrometry (SIMS), laser-ablation inductively coupled plasma mass spectrometry (laser-ablation ICP-MS) and Isotope ratio mass spectrometry (IRMS) have shown that a wealth of environmental information about water column stratification can be extracted from single shells of fossil foraminifera. Neogloboquadrina pachyderma (sinistral) (Nps), grows its chambers (ontogenetic calcite) near the Arctic surface, and subsequently sinks through the water column where it adds a thick calcite crust around the thinly calcified chambers at sub-mixed layer depths. Thus, each individual Nps shell contains chemical and isotopic zonation from waters with distinctly different physical properties ? the generally cold low salinity surface mixed layer and warmer subsurface halocline. Intrashell variability can be measured with in situ analytical approaches. The principal investigators (PIs) propose to apply a multi-instrument approach to quantify intrashell geochemistry in Nps shells obtained from an array of boxcore samples across the Arctic Ocean. They plan to combine intrashell ä18O and ä13C measurements in 5 ìm-sized domains by SIMS with analyses of Mg/Ca (proxy for temperature), Ba/Ca (proxy for river runoff or meltwater discharge), and Na/Ca (proxy for salinity) by laser-ablation ICP-MS on the same Nps shells. The innovative SIMS ultra-small domain isotope analytical approach was developed within the last few years by PI Kozdon, and calibrated in the lab of PI Spero. Both SIMS (spot-measurements) and laser-ablation data (depth profiles through the calcite layers) can be correlated to well defined domains in the foraminiferal shells that reflect a specific stage in the specimens? ontogenetic development (?time-markers?). Each of the measurements can be assigned to a general water depth range that is related to the depth of calcite addition as Nps migrates through the water column during its ontogenetic development. Thus, the proposed analytical approach provides an unprecedented opportunity to reconstruct past water column stratification between the surface and halocline from individual shells of Nps in sedimentary assemblages. This innovative multi-instrument approach will be applied to mid-Holocene and late Holocene Nps shells from ~50 14C-dated box-coretop samples from the Arctic Ocean. The cores will be carefully selected, mainly from U.S. core repositories, using the following criteria: (I) good coverage of the Arctic Ocean with a focus on key-areas sensitive to changes in water mass stratification and (II) existing 14C dates, although some of the cores will still need to be dated.

在过去的几十年里，北极变暖的速度大约是整个北半球的两倍，这与过去十年来北极海冰的大幅后退和变薄有关。与北极海冰变暖和变小有关的是北冰洋表层和深水环流的重组，但对相关过程的了解有限。早到中全新世提供了一个冰川后的类似于季节性无冰的北冰洋，类似于未来几十年所提出的情景。这种早-中全新世海冰极小值，在1万年前，通常被归因于太阳强迫的变化。然而，在海冰覆盖最小的时期，提供北极上层水柱分层的信息的记录很少。正常的古海洋学水团分层指标不能应用于北极地区；重建水柱水文需要不同的方法。拟议的研究有可能极大地提高我们对全新世早期至中期海冰最低期的过去北极水柱水文的了解，并为北冰洋未来状况的设想发展提供信息。该项目将通过支持一名博士生的培训来促进劳动力发展。所开发的技术将通过正式讲习班主动转让给国际科学界。结合使用二次离子质谱仪(SIMS)、激光烧蚀电感耦合等离子体质谱(激光消融电感耦合等离子体质谱)和同位素比质谱仪(IRMS)的最新创新表明，可以从化石的单个贝壳中提取丰富的关于水柱分层的环境信息。Neogloboquina pachyderma(Sinistral)(NPS)，在北极表面附近生长其洞室(个体生方解石)，随后通过水柱下沉，在次混合层深度的薄钙化洞室周围添加厚厚的方解石结壳。因此，每个单独的核动力源外壳都包含来自具有明显不同物理性质的水域的化学和同位素分区？总体较冷的低盐度表层混合层和较暖的次表层盐跃层。可用现场分析方法测量壳内变异性。首席调查员建议采用一种多仪器方法来量化从北冰洋的一系列盒状岩芯样品中获得的核动力源壳层中的贝壳内地球化学。他们计划将SIMS在5？m大小的区域中对Intrashellä18O和ä13C的测量与相同NPS外壳上的激光消融电感耦合等离子体质谱(ICMS)对镁/钙(代表温度)、钡/钙(代表河流径流或融水排放)和钠/钙(代表盐度)的分析相结合。创新的SIMS超小域同位素分析方法是由Pi Kozdon在最近几年开发的，并在Pi Spero的实验室进行了校准。SIMS(斑点测量)和激光消融数据(方解石层的深度剖面)都可以与有孔虫贝壳中明确定义的区域相关联，这些区域反映了标本中的特定阶段？个体发育(时间标记物)。每一次测量都可以被分配到一个一般的水深范围，该范围与NPS在个体发育过程中通过水柱迁移时方解石添加的深度有关。因此，所提出的分析方法提供了一个前所未有的机会，可以从沉积组合中NPS的单个贝壳重建地表和盐跃层之间的过去水柱分层。这种创新的多仪器方法将应用于来自北冰洋约50个14C年代的盒状岩心顶部样品的中全新世和晚全新世NPS贝壳。将使用以下标准仔细选择岩芯，主要是从美国的岩心储存库中选择：(I)对北冰洋的良好覆盖，重点放在对水团分层变化敏感的关键区域，以及(Ii)现有的14C日期，尽管一些岩芯仍需确定日期。

项目成果

High‐Resolution Mg/Ca and δ 18 O Patterns in Modern Neogloboquadrina pachyderma From the Fram Strait and Irminger Sea

弗拉姆海峡和伊尔明格海现代 Neogloboquadrina 厚皮藻中的高分辨率 Mg/Ca 和 δ 18 O 模式

• DOI: 10.1029/2020pa003969
• 发表时间: 2020
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: Livsey, Caitlin M.;Kozdon, Reinhard;Bauch, Dorothea;Brummer, Geert‐Jan A.;Jonkers, Lukas;Orland, Ian;Hill, Tessa M.;Spero, Howard J.
• 通讯作者: Spero, Howard J.