Measuring Dissolved Gases to Reveal the Processes that Drive the Solubility Pump and Determine Gas Concentration in Antarctic Bottom Water

在南极海岸附近，波利尼亚是开阔的水域，冬季极端的热量流失会导致海水变得冷、咸和稠密，足以沉入深海。这种高密度水的形成具有地区性和全球性的重要性，因为它影响着洋流系统。波尼亚过程还与形成的海冰的数量、海洋热量流失到大气中以及被南大洋吸收的大气二氧化碳有关。不幸的是，在南极冬季，影响深海水性质的海-气相互作用很难直接观测到。该项目将结合现场测量和实验室实验，调查溶解在海水中的稀有气体(氦、氦、氩、氙气和氪)浓度的差异是否与它们形成时的环境条件有关。如果是这样的话，稀有气体浓度可以提供对控制大陆架和底层水性质的机制的洞察，并可用于重建过去的气候条件。项目成果将有助于南大洋观测系统(SOOS)关于南大洋碳吸收的未来和后果的主题。该项目还将在环境监测、地球和海洋科学方法方面培训本科生和研究生。要了解南极沿海过程与深海系统变化之间的因果联系，就需要研究冬季多尼亚过程。冬季强烈的海洋热损失和海冰产生影响了南极两个重要的水团：高盐度陆架水(HSSW)和南极底层水(AABW)，从而影响海洋溶解度泵的强度和经向翻转环流。为了更好地表征海冰覆盖、海洋-大气交换、盐水拒绝和冰川融化如何影响AABW和HSSW的物理特性，该项目将分析2017年风笛号冬季巡航期间从两个罗斯海多年生生物收集的样本和数据。气体浓度将在由CTD玫瑰花环、水下质谱仪和台式膜进气质谱仪收集的海水样本中进行测量。稀有气体浓度将揭示地表水转化为HSSW和AABW时存在的海洋-大气(DIS)平衡，并提供过去条件的指纹。此外，还将使用氮(N_2)、氧(O_2)、Ar和CO_2浓度来确定净代谢平衡，并评估N_2作为O2的替代品作为冰川融水示踪剂的有效性。实验室实验将确定海冰形成过程中的气体分配率。调查结果将与风笛手和相关项目进行综合，从而对冬季南极海岸系统在深水组成方面的作用提供一个综合的看法。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Near the Antarctic coast, polynyas are open-water regions where extreme heat loss in winter causes seawater to become cold, salty, and dense enough to sink into the deep sea. The formation of this dense water has regional and global importance because it influences the ocean current system. Polynya processes are also tied to the amount of sea ice formed, ocean heat lost to atmosphere, and atmospheric CO2 absorbed by the Southern Ocean. Unfortunately, the ocean-atmosphere interactions that influence the deep ocean water properties are difficult to observe directly during the Antarctic winter. This project will combine field measurements and laboratory experiments to investigate whether differences in the concentration of noble gasses (helium, neon, argon, xenon, and krypton) dissolved in ocean waters can be linked to environmental conditions at the time of their formation. If so, noble gas concentrations could provide insight into the mechanisms controlling shelf and bottom-water properties, and be used to reconstruct past climate conditions. Project results will contribute to the Southern Ocean Observing System (SOOS) theme of The Future and Consequences of Carbon Uptake in the Southern Ocean. The project will also train undergraduate and graduate students in environmental monitoring, and earth and ocean sciences methods. Understanding the causal links between Antarctic coastal processes and changes in the deep ocean system requires study of winter polynya processes. The winter period of intense ocean heat loss and sea ice production impacts two important Antarctic water masses: High-Salinity Shelf Water (HSSW), and Antarctic Bottom Water (AABW), which then influence the strength of the ocean solubility pump and meridional overturning circulation. To better characterize how sea ice cover, ocean-atmosphere exchange, brine rejection, and glacial melt influence the physical properties of AABW and HSSW, this project will analyze samples and data collected from two Ross Sea polynyas during the 2017 PIPERS winter cruise. Gas concentrations will be measured in seawater samples collected by a CTD rosette, from an underwater mass-spectrometer, and from a benchtop Membrane Inlet Mass Spectrometer. Noble gas concentrations will reveal the ocean-atmosphere (dis)equilibrium that exists at the time that surface water is transformed into HSSW and AABW, and provide a fingerprint of past conditions. In addition, nitrogen (N2), oxygen (O2), argon, and CO2 concentration will be used to determine the net metabolic balance, and to evaluate the efficacy of N2 as an alternative to O2 as glacial meltwater tracer. Laboratory experiments will determine the gas partitioning ratios during sea ice formation. Findings will be synthesized with PIPERS and related projects, and so provide an integrated view of the role of the wintertime Antarctic coastal system on deep water composition.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.