Tracing dust input to the global ocean using thorium isotopes in marine sediments: ThoroMap
Tracing dust input to the global ocean using thorium isotopes in marine sediments: ThoroMap
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DOI：
10.1002/2016gb005408
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发表时间：
2016-10
影响因子：
5.2
通讯作者：
S. Kienast;G. Winckler;J. Lippold;S. Albani;N. Mahowald
中科院分区：
文献类型：
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作者：
S. Kienast;G. Winckler;J. Lippold;S. Albani;N. Mahowald
大陆沙尘输入海洋 - 大气系统对生物地球化学循环和全球气候具有重大影响，但对海洋中沙尘沉降的直接观测仍然稀少。与大洋地壳以及类似大洋中脊玄武岩的火山成因物质相比，长寿命同位素钍 - 232（²³²Th）在上部大陆地壳中大量富集。在远离大陆物质的河流和冰筏来源的开阔海洋沉积物中，²³²Th通常被认为主要是风成来源。结合基于颗粒活性放射性同位素钍 - 230（²³⁰Th）的通量归一化，海洋沉积物中²³²Th的测量是现代和过去海洋中沙尘积累的一种有前景的替代指标。在此，我们展示了ThoroMap，这是一个关于²³⁰Th归一化的²³²Th通量的新的全球数据汇编。经过仔细筛选，我们得出了全球海洋在全新世晚期（0 - 4千年）和末次盛冰期（LGM，19 - 23千年）的平均沙尘沉降估计值。将ThoroMap与从社区气候系统模型（CCSM3）和CCSM4（两个耦合的大气、陆地、海洋和海冰模型）得出的沙尘沉降估计值进行了比较。全新世晚期模型 - 数据相关系数为0.63（CCSM3）和0.59（CCSM4），末次盛冰期为0.82（CCSM3）和0.83（CCSM4）。ThoroMap是第一个基于单一、特定的沙尘替代指标构建的汇编，并且专门使用通量归一化来推导沙尘沉降率。
Continental dust input into the ocean‐atmosphere system has significant ramifications for biogeochemical cycles and global climate, yet direct observations of dust deposition in the ocean remain scarce. The long‐lived isotope thorium‐232 (232Th) is greatly enriched in upper continental crust compared to oceanic crust and mid‐ocean ridge basalt‐like volcanogenic material. In open ocean sediments, away from fluvial and ice‐rafted sources of continental material, 232Th is often assumed to be of predominantly eolian origin. In conjunction with flux normalization based on the particle reactive radioisotope thorium‐230 (230Th), 232Th measurements in marine sediments are a promising proxy for dust accumulation in the modern and past ocean. Here we present ThoroMap, a new global data compilation of 230Th‐normalized fluxes of 232Th. After careful screening, we derive dust deposition estimates in the global ocean averaged for the late Holocene (0–4 ka) and the Last Glacial Maximum (LGM, 19–23 ka). ThoroMap is compared with dust deposition estimates derived from the Community Climate System Model (CCSM3) and CCSM4, two coupled atmosphere, land, ocean, and sea ice models. Model‐data correlation factors are 0.63 (CCSM3) and 0.59 (CCSM4) in the late Holocene and 0.82 (CCSM3) and 0.83 (CCSM4) in the LGM. ThoroMap is the first compilation that is built on a single, specific proxy for dust and that exclusively uses flux‐normalization to derive dust deposition rates.