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首页> 外文期刊>Paleoceanography >Characterizing seawater oxygen isotopic variability in a regional ocean modeling framework: Implications for coral proxy records
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Characterizing seawater oxygen isotopic variability in a regional ocean modeling framework: Implications for coral proxy records

机译：在区域海洋建模框架中表征海水氧同位素变异性：对珊瑚代理记录的影响

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摘要

Reconstructions of the El Nino-Southern Oscillation (ENSO) are often created using the oxygen isotopic ratio in tropical coral skeletons (delta O-18). However, coral delta O-18 can be difficult to interpret quantitatively, as it reflects changes in both temperature and the delta O-18 value of seawater. Small-scale (10-100 km) processes affecting local temperature and seawater delta O-18 are also poorly quantified and contribute an unknown amount to intercoral delta O-18 offsets. A new version of the Regional Ocean Modeling System capable of directly simulating seawater delta O-18 (isoROMS) is therefore presented to address these issues. The model is used to simulate delta O-18 variations over the 1979-2009 period throughout the Pacific at coarse (O(50 km)) resolution, in addition to 10 km downscaling experiments covering the central equatorial Pacific Line Islands, a preferred site for paleo-ENSO reconstruction from corals. A major impact of downscaling at the Line Islands is the ability to resolve fronts associated with tropical instability waves (TIWs), which generate large excursions in both temperature and seawater delta O-18 at Palmyra Atoll (5.9 degrees N, 162.1 degrees W). TIW-related sea surface temperature gradients are smaller at neighboring Christmas Island (1.9 degrees N, 157.5 degrees W), but the interaction of mesoscale features with the steep island topography nonetheless generates cross-island temperature differences of up to 1 degrees C. These nonlinear processes alter the slope of the salinity: seawater delta O-18 relationship at Palmyra and Christmas, as well as affect the relation between coral delta O-18 and indices of ENSO variability. Consideration of the full physical oceanographic context of reef environments is therefore crucial for improving delta O-18-based ENSO reconstructions.
机译：厄尔尼诺-南方涛动（ENSO）的重建通常是利用热带珊瑚骨骼（δO-18）中的氧同位素比来实现的。但是，珊瑚三角洲O-18可能难以定量解释，因为它反映了温度和海水三角洲O-18值的变化。影响局部温度和海水三角洲O-18的小规模过程（10-100 km）也量化较差，并且对珊瑚间三角洲O-18偏移的贡献量未知。因此，提出了一种能够直接模拟海水三角洲O-18（isoROMS）的区域海洋建模系统的新版本来解决这些问题。该模型用于模拟整个太平洋在1979-2009年期间以粗略（O（50 km））分辨率划分的O-18三角洲变化，此外还进行了覆盖中部赤道太平洋太平洋岛屿的10 km缩小实验，珊瑚的古ENSO重建。内陆群岛降尺度的一个主要影响是能够解决与热带不稳定波（TIW）相关的前沿的能力，热带不稳定波在Palmyra环礁（北纬5.9度，北纬162.1度）上在温度和海水三角洲O-18上产生较大的偏移。与TIW相关的海面温度梯度在邻近的圣诞节岛处较小（北纬1.9度，西经157.5度），但中尺度特征与陡峭岛状地形的相互作用仍然会产生高达1摄氏度的跨岛温差。过程改变了盐度的斜率：巴尔米拉和圣诞节的海水三角洲O-18关系，以及影响珊瑚三角洲O-18与ENSO变异指数之间的关系。因此，对礁石环境的完整物理海洋环境的考虑对于改善基于三角洲O-18的ENSO重建至关重要。

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