Sea-surface dynamics diagnosed from satellite data and coupled models

海洋学和气候动力学中的一个中心问题涉及各种性质的地表异常的演变。海面温度异常调节上层海洋和大气之间的热量交换，深刻影响海洋环流、天气、季节循环、低频气候变化和气候变化。在高纬度地区，海面盐度异常与这种可变性以及生态系统的可变性有关。然而，目前尚不清楚如何解释海表面温度异常的发展和传播，这些异常通常是根据时空滞后相关性进行分析的。这种模糊性使得无论是在观察中还是在模型中，都很难约束潜在的机制。该项目的主要目标是诊断、量化和了解控制海洋表面温度和盐度异常传播的机制。这项研究将培训一名研究生，其结果将广泛传播给科学家和公众。该项目应用了研究人员开发的一个新框架，以了解地表异常如何传播和演化以及为什么传播和演化。特别是，这种新的方法通过将海表面温度演变分解为平流、扩散和松弛分量，极大地改进了早期的方法。将这一新方法应用于历史北大西洋海温数据和耦合气候模式输出的初步结果推动了这项研究。研究人员打算继续进行海表面温度分析，以利用全球观测，特别是卫星图像以及数值模型来量化异常动态。新的框架也适用于其他表面属性领域，如海面盐度。这项工作提出了三个问题：为什么海洋表面温度异常明显以不同的速度传播到底层洋流？为什么海表面温度和海面盐度异常表现不同？是什么决定了由它们推断出的横向扩散系数的变化？研究人员将使用包括耦合气候模型在内的一系列模型来确定控制这些领域异常演变的机制。

A central question in oceanography and climate dynamics concerns the evolution of surface anomalies of a wide range of properties. Sea surface temperature anomalies regulate the exchange of heat between the upper ocean and the atmosphere, profoundly influencing ocean circulation, weather, the seasonal cycle, low-frequency climate variability, and climate change. In high latitudes, sea surface salinity anomalies have been associated with such variability, and with variability in ecosystems. It is unclear how to interpret the development and propagation of sea surface temperature anomalies, however, which are often analyzed in terms of spatiotemporally-lagged correlations. This ambiguity makes it difficult to constrain the underlying mechanisms, both in observations and in models. The main goal of this project is to diagnose, quantify, and understand the mechanisms controlling the propagation of ocean surface anomalies in temperature and salinity. This study will train one graduate student and its results will be disseminated broadly to scientists and the general public.This project applies a new framework developed by the investigators to understand how and why surface anomalies propagate and evolve. In particular, this new method to infers sea surface temperature transport fields greatly improves on earlier approaches by decomposing sea surface temperature evolution into advective, diffusive and relaxation components. Preliminary results applying this new method to historical North Atlantic sea surface temperature data and coupled climate model output motivate this study. The researchers intend to continue the sea surface temperature analysis to quantify anomaly dynamics using global observations, especially satellite imagery, as well as numerical models. The new framework also applies to other surface property fields, such as sea surface salinity. Three questions emerge from this work: Why do sea surface temperature anomalies apparently propagate at different speeds to the underlying currents? Why do sea surface temperature and sea surface salinity anomalies behave differently? and What determines the variations in the lateral diffusivity inferred from them? The researchers will use a hierarchy of models, including coupled climate models, to identify the mechanisms controlling anomaly evolution in these fields.