Attribution of climate change in the subtropical North Atlantic Ocean: exploiting tritium-helium data and adjoint sensitivity analyses

北大西洋在其热含量和有机物的生物输出方面如何在气候系统中运作存在不确定性，这最终影响到海洋如何从大气中吸收多余的碳。例如，在过去50年中，北大西洋亚热带地区的热含量增加，这与上层温跃层水（18至24摄氏度）和冷温跃层沃茨（4至10摄氏度）的体积增加有关，但邻近其他温度等级的水却减少了。这项建议旨在了解如何亚热带北大西洋在气候系统中的运作，通过分析氚氦观测沿着36 N和25 W整个盆地。氚-氦年龄的推断提供了水最后一次与大气接触的时间。氚-氦年龄的测量将用于了解：1。通风如何控制在亚热带北大西洋观测到的热含量的变化; 2。确定有机物质的输出率，这是间接诊断的氧利用率使用氚氦年龄。将通过与环流模型及其伴随模型的比较来评估数据信号的可靠性。气候变化的敏感性，有机物的输出和营养物质的循环，然后将通过使用相同的模式及其伴随，有效地识别外部强迫和模式物理变化的影响。

There is uncertainity in how the North Atlantic operates in the climate system in terms of its heat content and biological export of organic matter, which ultimately affects how the ocean uptakes excess carbon from the atmosphere. For example, over the last 50 years, there has been an increase in heat content in the subtropical North Atlantic, associated with an increase in volume of both upper thermocline water (18 to 24C) and cold thermocline waters (4 to 10C), but a decrease in other neighbouring temperature classes. This proposal aims to understand how the subtropical North Atlantic operates in the climate system by analysing tritium-helium observations along 36N and 25W across the basin. The inferred tritium-helium age provides a measure of the elapsed time since the water was last in contact with the atmosphere. The measurements of tritium-helium age will be used to understand: 1. How ventilation controls the observed changes in heat content in the subtropical North Atlantic; 2. To identify the rate of export of organic matter which is diagnosed indirectly from the rate of oxygen utilisation using the tritium-helium age. The reliability of the data signals will be assessed by comparying with a circulation model and its adjoint. The sensitivity of the climate change, the export of organic matter and cycling of nutrients, will then be understood by using the same model and its adjoint, which efficiently identifies the effect of changes in external forcing and model physics.