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Upper-ocean variability in Drake Passage and the Weddell Sea: Measuring the oceanic response to air-sea and ice-ocean interactions.

机译：德雷克海峡和韦德尔海的上层海洋变化性：测量海洋对海-空和冰-海洋相互作用的反应。

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摘要

In the first part of this dissertation, reanalysis heat flux products and profiles from a 15 year time series of high-resolution, near-repeat expendable bathythermograph / expendable conductivity-temperature-depth (XBT/XCTD) sampling in Drake Passage are used to examine sources of upper-ocean variability, with a focus on the nature of MLD variations and their impact on a first-order, one-dimensional heat budget for the upper ocean in the regions north and south of the Polar Front. Results show that temperature and density criteria yield different MLD estimates, and that these estimates can be sensitive to the choice of threshold. The difficulty of defining MLD in low-stratification regions, the large amplitude of wintertime MLD (up to 700 m in Drake Passage), and the natural small-scale variability of the upper ocean result in considerable cast-to-cast variability in MLD, with changes of up to 200 m over 10 km horizontal distance. In contrast, the heat content over a fixed-depth interval of the upper ocean shows greater cast-to-cast stability and clearly measures the ocean response to surface heat fluxes. In particular, an annual cycle in upper ocean heat content is in good agreement with the annual cycle in heat flux forcing, which explains 24% of the variance in heat content above 400 m depth north of the Polar Front and 63% of the variance in heat content south of the Polar Front. At interannual timescales, the primary drivers of interannual variations in upper-ocean heat content in Drake Passage are advective processes; up to 40% of the variance of cross-Passage average upper-ocean heat content is due to meanders of the Polar Front, while 14% of the variability results from mesoscale eddies. Heat flux anomalies contribute less variance (5-10%) on interannual timescales. Teleconnections with ENSO and SAM contribute to anomalies in meridional winds and heat fluxes. As a result, ENSO and SAM contribute variability in upper ocean heat content at near-zero lags; ENSO and SAM are also correlated with upper ocean heat content anomalies on timescales of ~2-5 years.;The second part of this dissertation explores a melting iceberg as a source of upper-ocean variability. Observations near a large tabular iceberg in the Weddell Sea in March and April 2009 show evidence that water from ice melting below the surface is dispersed in two distinct ways. Warm, salty anomalies in T-S diagrams suggest that water from the permanent thermocline is transported vertically as a result of turbulent entrainment of meltwater at the iceberg's base. Stepped profiles of temperature, salinity, and density in the seasonal thermocline are more characteristic of double-diffusive processes that transfer meltwater horizontally away from the vertical ice face. These processes contribute comparable amounts of meltwater--O(0.1 m3) to the upper 200 m of a 1 m2 water column--but only basal melting results in significant upwelling of water from below the Winter Water layer into the seasonal thermocline. This suggests that these two processes may have different effects on vertical nutrient transport near an iceberg.
机译：在本文的第一部分中，使用了在Drake Passage中高分辨率，近重复的消耗性热浴仪/消耗性电导率-温度-深度（XBT / XCTD）采样的15年时间序列中的重新分析热通量产物和分布图上层海洋变化的主要来源，重点是MLD变化的性质及其对极地锋以南和北部地区上层海洋的一阶一维热预算的影响。结果表明，温度和密度标准会得出不同的MLD估计值，并且这些估计值可能对阈值的选择敏感。在低层地层中定义MLD的困难，冬季MLD的振幅较大（在Drake Passage中可达700 m）以及上层海洋的自然小尺度变化，导致MLD的铸铸变化很大，在10 km的水平距离内最大变化200 m。相反，在上层海洋的固定深度范围内的热量含量显示出较高的铸造至铸造稳定性，并清楚地测量了海洋对表面热通量的响应。特别是，高洋热量含量的年周期与热通量强迫的年周期非常吻合，这解释了极地锋以北400 m深度以上热量含量的24％和极地热变化的63％。极地以南的热量。在年际尺度上，德雷克海峡上层海洋热量含量年际变化的主要驱动力是对流过程；跨通道平均上层海洋热量的变化中，多达40％的变化是由于极地锋的弯曲造成的，而14％的变化是由中尺度涡旋产生的。在年际时间尺度上，热通量异常的变化较小（5-10％）。 ENSO和SAM的遥连接会导致子午风和热通量异常。结果，ENSO和SAM在接近零时滞的情况下贡献了较高的海洋热量。 ENSO和SAM也与约2-5年时间尺度上的上层海洋热量含量异常相关。;本论文的第二部分探讨了融化的冰山作为上层海洋变化的来源。 2009年3月和4月在韦德尔海的一个大型板状冰山附近观察到的证据表明，来自冰融化在地表以下的水以两种不同的方式分散。 T-S图表中的温暖，咸异常表明，由于冰山底部融化水的湍流夹带，来自永久性温跃层的水被垂直输送。季节性温跃层中温度，盐度和密度的阶梯状分布是双扩散过程的特征，该过程将融化水水平地转移离开垂直冰面。这些过程为1 m2水柱的上部200 m贡献了相当数量的熔融水-O（0.1 m3）-但是仅基础融化会导致水从冬季水层以下显着上升到季节性温跃层。这表明这两个过程可能对冰山附近的垂直养分传输有不同的影响。

著录项

  • 作者

    Stephenson, Gordon Ronald, Jr.;

  • 作者单位

    University of California, San Diego.;

  • 授予单位 University of California, San Diego.;
  • 学科 Physical oceanography.
  • 学位 Ph.D.
  • 年度 2012
  • 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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