Monitoring Global Ocean Heat Content Changes by Internal Tide Oceanic Tomography

海洋热含量(OHC)是全球气候变异性和变化的关键指标。然而，在全球范围内观察OHC是一个巨大的挑战。随着ARGO剖面浮子阵列的成熟，在空间和时间上具有良好覆盖率的观测只有在最近10年才能获得。这项研究将使用一种名为内潮汐海洋层析成像(ITOT)的方法获得1995-2014年间全球OHC变化的长达20年的记录，其中卫星测高数据被用于精确测量远程内潮汐的旅行时间。就像在声波断层扫描中一样，这些旅行时间被分析以推断OHC的变化。这一分析将使Argo Floats提供的10年时间序列翻一番。更重要的是，ITOT将为全球OHC变化提供一个独立的长期、低成本、环保的观测系统。由于海洋变暖极大地促进了海平面上升，从而对低洼沿海地区产生了重大后果，因此这些观测结果有可能产生直接的社会效益。该项目将直接向公众传达一些结果。该团队将制作一部教育动画，展示如何测量海洋变暖，以及从太空的有利位置如何使用新颖的ITOT技术。这部动画将为参观实验室的学生播放，并在当地K-12学校的科学讲座和节日中播放。此外，三名暑期本科生将接受数据分析和解释以及海报演示方面的培训。该项目中应用于全球海洋的分析技术是基于该小组已经进行的初步区域分析。将分析1995-2014年间约60个卫星年的高度计数据。具体地说，它将(1)量化全球M2和K1内潮的年变率、年际变率和双年变化趋势，(2)构造从内潮旅行时间变化到OHC变化的转换函数，(3)建立长达20年的全球OHC变化的记录，并使用ARGO测量来评估不确定性。该项目的最终目标是开发ITOT技术，用于未来的全球有机污染物监测。这将提高我们对全球OHC的时间和空间变异性的理解，特别是结合Argo浮标、XBTS和WOCE全深度水文地质的现场测量。ITOT的观测将对ECCO2提供有用的约束。内潮模型可用于改正ARGO和XBT测量中的内潮噪声。此外，产生的月度和年度内潮汐场将为全球高分辨率、允许涡流的内潮汐数值模式提供约束。

Ocean Heat Content (OHC) is a key indicator of global climate variability and change. However, it is a great challenge to observe OHC on a global scale. Observations with good coverage in space and time are only available in the last 10 years with the maturing of the Argo profiling float array. This study will obtain a 20-year-long record of global OHC changes from 1995-2014 with a method called Internal tide oceanic tomography (ITOT), in which the satellite altimetry data are used to precisely measure travel times for long-range internal tides. Just like in acoustic tomography, these travel times are analyzed to infer changes in OHC. This analysis will double the 10 years of time series available from Argo floats. More importantly, ITOT will provide an independent long-term, low-cost, environmentally-friendly observing system for global OHC changes. Since ocean warming contributes significantly to sea level rise, which has significant consequences to low-lying coastal regions, these observations have the potential for direct societal benefits. The project will communicate some of its results directly to the public. The team will make an educational animation showing how ocean warming is measured and how the novel ITOT technique works from the vantage point of space. This animation will be played for students visiting the lab, and in science talks and festivals in local K-12 schools. In addition, three summer undergraduate students will be trained in data analysis and interpretation, and poster presentation.The analysis technique to be applied over the global ocean in this project is based on the preliminary regional analysis already conducted by this team. About 60 satellite-years of altimeter data from 1995-2014 will be analyzed. Specifically, it will (1) quantify annual variability, interannual variability, and bidecadal trend in global M2 and K1 internal tides, (2) construct the conversion function from the internal tide's travel time changes to OHC changes, and (3) construct a record of 20-year-long global OHC changes, and assess uncertainties using Argo measurements. The ultimate goal for this project is to develop the ITOT technique for future global OHC monitoring. This will improve our understanding of the temporal and spatial variability of global OHC, particularly in combination with in situ measurements from Argo floats, XBTs, and WOCE full-depth hydrography. The ITOT observations will provide useful constraints to ECCO2. The internal tide models may be used to correct internal tide noise in the Argo and XBT measurements. In addition, the monthly and yearly internal tide fields produced will provide constraints to global high-resolution, eddy-permitting numerical models of internal tides.