Advancing Refractometry for the Measurement of Absolute Salinity

精确测量海洋盐度和密度对海洋科学的几乎所有领域都至关重要。其中包括海洋环流和混合、生物生产力、营养物运输、污染物扩散以及海洋储存热量和二氧化碳的能力。 几十年来，测量盐度和密度的大部分现场工作都依赖于传统的传感器，用于检测海洋水体及其界面的电导率和温度，从毫米到全球尺度。 然而，用于测量盐度的电导率传感器由于其温度交叉敏感性并且因为它们检测海水的电荷而不是其真实质量而仍然具有缺点。 因此，测量折射率已被建议作为测量电导率的补充和在许多情况下的上级替代方案。 例如，折射率对温度的低敏感性使其对研究驱动世界上许多洋流并影响全球气候的北极泵特别有价值。 然而，传统上测量折射率的困难在于测量必须具有非凡的精度。 然而，现代光学技术已经开始增加其可行性。 因此，该项目寻求开发和利用两种技术，这两种技术将首次能够准确测量海洋中的折射率和绝对盐度。第一项技术是改进现有实验性海上折射仪的现场折射仪。 第二项技术是开发海水折射率精确状态方程所需的台式设备。 到目前为止，没有足够的实验参考数据来比较海水指数的测量。 因此，开发能够产生这些数据的设备是折射率实用化的关键步骤。 总体而言，这项工作中开发的技术将为在观测海洋学中广泛使用的额外测量（折射率）提供方法和实验参考数据。该奖项反映了NSF的法定使命，并通过使用基金会的知识产权进行评估，被认为值得支持。优点和更广泛的影响审查标准。

Accurate measurements of ocean salinity and density are critical for almost all areas of ocean science. Some of these include, ocean circulation and mixing, biological productivity, nutrient transport, pollutant dispersal, and the ocean’s capacity to store heat and carbon dioxide. For decades, much of the field work to measure salinity and density has relied upon traditional sensors for detecting conductivity and temperature within ocean water masses and at their interfaces, and from millimeter to global scales. However, conductivity sensors for measuring salinity still have shortcomings due to their temperature cross-sensitivity and because they detect the electrical charge of seawater instead of its true mass. Accordingly, measuring refractive index has been suggested as a complimentary and in many cases superior alternative to measuring conductivity. For example, refractive index’s low sensitivity to temperature makes it particularly valuable for studying the arctic pumps which drive many of the world’s currents and influence global climate. The difficulty with measuring refractive index, however, has traditionally been the extraordinary precision with which the measurement must be made. Nevertheless, modern optics technologies have begun to increase its feasibility. Accordingly, this project seeks to develop and utilize two technologies that together will, for the first time, enable accurate measurements of refractive index and Absolute Salinity in the ocean. The first technology is an in-situ refractometer that improves upon an existing experimental seagoing refractometer. The second technology is the benchtop equipment necessary for developing an accurate equation-of-state for seawater refractive index. To date, no sufficient experimental reference data exists for which to compare seawater index measurements. Thus, developing equipment capable of producing this data is a critical step for refractive index’s utility. Overall, the technologies developed in this work will provide the means and the experimental reference data for an additional measurement, the refractive index, to be widely used in observational oceanography.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.