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A study of oceanic responses to mesoscale processes in the Middle Atlantic Bight.

机译：对中大西洋海岸线中海尺度过程的海洋响应的研究。

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摘要

The responses of the ocean to several mesoscale processes in the Middle Atlantic Bight (MAB), including the phytoplankton blooms, the cold pool and the horizontal heat advection, are investigated on different time scales using multi-sensor data including in-situ measurements, satellite observations and reanalysis data.;Taking the 2011 summer bloom as a study case, we investigated the transport and nutrient delivery mechanisms are investigated for large phytoplankton blooms of the New Jersey coast. The horizontal advection of the chlorophyll is approximately one order larger than the horizontal diffusion averaging the whole study area. And the sea surface currents are found to correlate with the wind stress but only for part of the middle shelf. Based on the horizontal advection simulation driven by HF radar current, the bloom is divided into three sub-regions. The northern coastal section of the bloom shows high-low-high pattern in chlorophyll time series, which is related to coastal upwelling and an anticyclonic eddy. Coastal currents play an important role in the eddy formation and the southward transport of the bloom. The southern coastal section of the bloom is supported by the nutrients from coastal upwelling and driven offshore by wind. The northeast section of the bloom is fueled by nutrient source upwelled through Ekman pumping. The magnitude of Ekman pumping is of the same order as the magnitude of the upwelling along the coast. These identified mechanisms could also be applied to more than half of bloom events during 2002 to 2013. In the summer of 2011 off the coast of New Jersey, processes in different sub-regions worked together, leading to this large phytoplankton bloom.;The influence of the cold pool in the Middle Atlantic Bight (MAB) to cross-shelf sea surface slope is explored by fitting an annual harmonic to temperature and salinity profiles from 1993 to 2012, and comparing to the 20-year-averaged altimetry sea level anomaly (SLA). The consistency within bottom temperature, thermal steric height, total steric height and altimetry observation validates that the cold pool induces depressed sea level in the middle shelf overlapping with the dominant surface seasonal cycles. Temporally, the cold pool pattern is most apparent in July and August as a result of magnitude competition between the thermal and haline steric height. In addition, Ensemble Empirical Mode Decomposition (EEMD) is employed to reconstruct the altimetry SLA and reveals the middle-shelf depression pattern from single year's SLA data. The locations of the SLA depression from 1993 to 2012 agree with the cold pool locations identified from in-situ measurements, suggesting a promising application of altimetry SLA in the cold pool study.;Conclusively the modulation of the cross-shelf sea level variation by the cold pool is revealed, which contributes to the understanding of the sea level response to water masses on the continental shelf. Continuous satellite observations from 1992 to 2012 allow to investigate the contribution of the horizontal heat flux to the upper layer heat budget on different time scales over the middle and outer shelf of MAB. On the seasonal scale, the shelf averaged temperature variations are controlled by the vertical heat flux. On longer time scales, the temporal temperature variations are determined by the competition between the vertical heat flux and the horizontal heat advection. The horizontal heat diffusion is relatively small comparing to other terms in the heat budget. In the upper mixed layer, the heat advection due to the sloping sea surface is comparable to the magnitude of the wind-induced Ekman transport, each of which has different spatial distribution over the shelf. The interactions among different time scales (the sub-seasonal, seasonal, interannual, long-term scales and the mean) of the heat advection are quantitatively evaluated. For the advection related to the geostrophic currents, the largest components are the seasonal temperature by the mean currents, the mean temperature by the sub-seasonal currents, and the seasonal temperature by the sub-seasonal currents. They together contributing 80% to the total energy of the heat advection. For the advection associated with the Ekman currents, the largest components are the seasonal temperature by the mean Ekman currents, and the seasonal temperature by the seasonal Ekman currents. The relative magnitudes of temporal components are determined by the spectral distribution of the temperature and currents. Spectral analysis on the temporal components also suggests that the variations of the horizontal heat advection on specific time scales are contributed from multiply time scale variations. Through the detailed investigations on the mesoscale processes in the MAB, including the chlorophyll concentrations, the sea level and the heat advections, my work improves the understanding of the coastal ocean variations on different time scales, facilitates better interpretation of the observations, and clarifies the linkage among different variables. Moreover, climate change and the varying ocean are placing new challenges to coastal researchers. This dissertation enables further investigations of the coastal ocean responses to the climate change.
机译：使用包括实地测量，卫星观测在内的多传感器数据，在不同的时间尺度上研究了海洋对中大西洋海岸线（MAB）几个中尺度过程的响应，包括浮游植物的开花，冷池和水平热对流。观测和再分析数据。以2011年夏季盛华为研究案例，我们研究了新泽西州海岸大型浮游植物盛华的运输和养分输送机制。叶绿素的水平对流比整个研究区域平均水平扩散的水平大约大一个数量级。并且发现海面洋流与风应力相关，但仅在中层架的一部分。基于高频雷达电流驱动的水平对流模拟，将水华分为三个子区域。水华的北部沿海地区在叶绿素时间序列中呈高-低-高模式，这与海岸上升流和反气旋涡有关。洋流在涡流的形成和水华的南移中起着重要作用。水华的南部沿海部分由沿海上升流中的营养物质支持，并被风驱至海上。通过Ekman抽水将营养源向上注入，从而使水华的东北部分获得了动力。 Ekman抽水的幅度与沿海岸上升流的幅度相同。这些确定的机制也可以应用于2002年至2013年期间一半以上的盛华事件。2011年夏天，在新泽西州海岸附近，不同子区域的过程协同工作，导致了这种大型浮游植物的盛华。通过将1993年至2012年的年谐波与温度和盐度曲线拟合，并与20年平均测高海平面异常进行比较，探索了中大西洋海岸线（MAB）的冷池与跨海平面坡度之间的关系（ SLA）。底部温度，热空间高度，总空间高度和测高仪观测值之间的一致性验证了冷池在中陆架上诱发海平面下降，并与主要地表季节周期重叠。暂时而言，由于热和卤代空间高度之间的量级竞争，冷池模式在7月和8月最为明显。此外，采用集成经验模态分解（EEMD）来重建测高仪的SLA，并从单年的SLA数据揭示了中层架凹陷模式。从1993年到2012年SLA凹陷的位置与从原位测量中确定的冷池位置一致，这表明高空SLA在冷池研究中有希望的应用;最终通过跨海平面海平面变化的调制揭示了冷池，这有助于了解海平面对大陆架上水团的响应。从1992年到2012年连续进行的卫星观测可以调查MAB中部和外部架子在不同时间尺度上水平热通量对上层热量收支的贡献。在季节性尺度上，货架平均温度变化由垂直热通量控制。在较长的时间尺度上，时间温度的变化取决于垂直热通量和水平热对流之间的竞争。与热量预算中的其他术语相比，水平热量扩散相对较小。在上层混合层中，由于海面倾斜而产生的热对流与风引起的埃克曼输运的强度相当，两者在架子上都有不同的空间分布。对流平流的不同时间尺度（亚季节，季节，年际，长期尺度和平均值）之间的相互作用进行定量评估。对于与地转流相关的平流，最大的分量是平均温度的季节温度，次季节电流的平均温度和次季节电流的季节温度。它们共同为热对流的总能量贡献了80％。对于与埃克曼洋流相关的平流，最大的分量是平均埃克曼洋流的季节性温度，以及季节性埃克曼洋流的季节性温度。时间分量的相对大小由温度和电流的频谱分布确定。对时间分量的频谱分析还表明，水平热对流在特定时间尺度上的变化是由多个时间尺度的变化引起的。通过对人与生物圈计划中尺度过程的详细调查，包括叶绿素浓度，海平面和热对流，我的工作增进了对不同时间尺度上沿海海洋变化的理解。有助于更好地解释观测结果，并阐明不同变量之间的联系。此外，气候变化和海洋变化给沿海研究人员提出了新的挑战。本文为进一步研究沿海海洋对气候变化的反应提供了可能。

著录项

  • 作者

    Sha, Jin.;

  • 作者单位

    University of Delaware.;

  • 授予单位 University of Delaware.;
  • 学科 Physical oceanography.;Climate change.;Remote sensing.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 136 p.
  • 总页数 136
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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