A Multivariate Empirical Orthogonal Function Method to Construct Nitrate Maps in the Southern Ocean

AbstractThe ability to construct nitrate maps in the Southern Ocean (SO) from sparse observations is important for marine biogeochemistry research, as it offers a geographical estimate of biological productivity. The goal of this study is to infer the skill of constructed SO nitrate maps using varying data sampling strategies. The mapping method uses multi-variate Empirical Orthogonal Functions (MEOFs) constructed from nitrate, salinity, and potential temperature (N-S-T) fields from a biogeochemical general circulation model simulation. Synthetic N-S-T datasets are created by sampling modeled N-S-T fields in specific regions, either determined by random selection or by selecting regions over a certain threshold of nitrate temporal variances. The first five hundred MEOF modes, determined by their capability to reconstruct the original N-S-T fields, are projected onto these synthetic N-S-T data to construct time-varying nitrate maps. Normalized root-mean-square errors (NRMSEs) are calculated between the con...