Reconstruction of subsurface ocean state variables using Convolutional Neural Networks with combined satellite and in situ data

Abstract

Subsurface ocean measurements are extremely sparse and irregularly distributed, narrowing our ability to describe deep ocean processes and thus also limiting our understanding of the role of ocean and marine ecosystems in the Earth system. To overcome these observational limitations, neural networks combining remotely-sensed surface measurements and in situ vertical profiles are increasingly being used to retrieve high-quality three-dimensional estimates of the ocean state. This study proposes a convolutional neural network (CNN) architecture for the reconstruction of vertical profiles of temperature and salinity starting from surface observation-based data. The model is trained on satellite and in situ data collected between 2005 and 2020 in the Atlantic Ocean. Rather than using spatially gridded in situ observations, we use directly measured vertical profiles. Different combinations of surface variables are analyzed and compared in order to determine the most effective inputs for the CNN. Furthermore, the relative importance of each of these variables in the vertical reconstruction is assessed using Shapley values, originally developed in the framework of cooperative game theory. The model performance is shown to be superior to current state-of-the-art methods and the same approach can easily be extended to other basins or to the global ocean.

DSE-NN: Discretized Spatial Encoding Neural Network for Ocean Temperature and Salinity Interpolation in the North Atlantic

“…Interpolation techniques for ocean temperature and salinity are pivotal components of marine scientific research, significantly contributing to the comprehension of ocean dynamics, global climate change, and the sustenance of marine ecosystems [1][2][3]. With advancements in observational technologies and innovations in data processing methodologies, this domain has witnessed remarkable progress-particularly with the application of neural networks, which has greatly propelled the evolution of ocean temperature and salinity interpolation techniques [4]. In early research endeavors, traditional interpolation methods such as optimal interpolation (OI), Kriging interpolation, and triangular mesh linear interpolation were extensively applied for the processing of ocean temperature and salinity data [5][6][7].…”