Mechanisms of Intrinsic and Anthropogenically Forced Climate Variations

受海-气热量交换、降雨和蒸发的影响，海洋最上层的浮力会影响颠覆的大洋环流。海面上的风可以产生洋流，促进混合。风和浮力对海洋的综合影响最终会在整个海洋中感受到。随着海洋条件的变化(特别是海洋表面温度或SST)，大气环流可以控制云和雨的模式，这反过来又影响风和浮力对海洋的作用。为此，涉及海气界面浮力和风的机制对于确定我们在气候模型中观察和模拟的许多气候变化的时间尺度、模式和幅度至关重要。然而，由于稀少的海洋观测和复杂的动力学，对这些机制的完全了解仍然难以捉摸。这项研究将利用气候模型实验分解风和浮力强迫的相对影响，重点放在两个预计将在未来气候中发生重大变化的特征，即表面温度和大西洋子午线翻转环流(AMOC)。特别是关于风和浮力强迫作为大气向海洋传递内在和外部强迫变化的途径的重要性，许多悬而未决的问题仍然存在。由于模型层次结构中的巨大差距，解决这些问题变得更加困难，前者是完全耦合的模型，后者是海洋和大气的完整动力学表示，后者将海洋表示为只与大气热耦合的静止平板。这项工作将通过利用气候模式的机械去耦合(MD)版本来弥合模型层次中的所述差距来实施，该版本将海洋环流中仅由浮力驱动的变化与完全耦合模型捕获的风致可变性隔离开来。由于MD作为完全耦合海洋模式和板条海洋模式之间的中间步骤，从机制上更清楚地理解气候变化的驱动因素是可能的。这三个模型版本将一起用于确定浮力和风变化在驱动固有的SST变异性、表面温度的人为趋势以及固有的和人为强迫的AMOC变化中的相对作用。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。

Influenced by air-sea heat exchange, rainfall, and evaporation, the buoyancy of the ocean’s uppermost layer can impact the overturning oceanic circulation. Winds above the ocean surface can generate currents and promote mixing. The combined effects of wind and buoyancy on the ocean are ultimately felt throughout the entire ocean. In response to the changing ocean conditions (especially, the sea surface temperature or SST), atmospheric circulations can arise to govern patterns of clouds and rain, which in turn impact the wind and buoyancy forcings on the ocean. To this end, mechanisms involving buoyancy and winds at the air-sea interface are critical in establishing the timescales, patterns, and amplitudes of many climate variations we observe and simulate in climate models. Yet, complete understanding of these mechanisms remains elusive due to sparse ocean observations and complicated dynamics. The research will decompose the relative effects of winds versus buoyancy forcing using climate model experiments, with emphasis on two features expected to substantially change in a future climate, namely the surface temperature and the Atlantic Meridional Overturning Circulation (AMOC).In particular, many open questions remain about the importance of winds versus buoyancy forcing as pathways through which the atmosphere communicates intrinsic and externally forced variations to the ocean. Addressing these questions is made more difficult by a wide gap in the model hierarchy, between fully coupled models with a complete dynamical representation of both the ocean and atmosphere and models that represent the ocean as a motionless slab that is only thermally coupled to the atmosphere. This work will be implemented by closing said gap in the model hierarchy via leveraging a mechanically decoupled (MD) version of a climate model, which isolates variations in the ocean circulation that are driven solely by buoyancy from the wind-driven variability captured by fully coupled models. With the MD as an intermediate step between fully coupled and slab ocean models, a clearer mechanistic understanding of the drivers of climate variations is possible. These three model versions will be used together to identify the relative roles of buoyancy and wind variations in driving intrinsic SST variability, anthropogenic trends in surface temperature, and intrinsic and anthropogenically forced AMOC variations.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.