Mikael Kuusela
Carnegie Mellon University

Abstract:
Argo floats measure seawater temperature and salinity in the upper 2,000 m of the global ocean. Statistical analysis of the resulting spatio-temporal data set is challenging due to its nonstationary structure and large size. We propose mapping these data using locally stationary Gaussian process regression where covariance parameter estimation and spatio-temporal prediction are carried out in a moving-window fashion. This yields computationally tractable nonstationary anomaly fields without the need to explicitly model the nonstationary covariance structure. We also investigate Student-t distributed fine-scale variation as a means to account for non-Gaussian heavy tails in ocean temperature data. Cross-validation studies comparing the proposed approach with the existing state-of-the-art demonstrate clear improvements in point predictions and show that accounting for the nonstationarity and non-Gaussianity is crucial for obtaining well-calibrated uncertainties. I will conclude by briefly describing on-going work on using these methods to obtain improved estimates of ocean climate and dynamics.

Bio:
Dr. Mikael Kuusela is an Assistant Professor of Statistics and Data Science at Carnegie Mellon University where he develops statistical methods for analyzing large and complex data sets in the physical sciences. His recent work has had two focal points: 1) developing spatio-temporal interpolation methods for analyzing oceanographic data from Argo profiling floats and 2) uncertainty quantification in ill-posed inverse problems with applications to the unfolding problem at the Large Hadron Collider at CERN. He obtained his PhD in Statistics in July 2016 from EPFL in Lausanne, Switzerland. He then moved to the US where he was a postdoc at the University of Chicago and at SAMSI before joining Carnegie Mellon in August 2018. His BSc and MSc degrees are in Engineering Physics and Mathematics from Aalto University.

Host:
Arno Solin
Assistant Professor in Machine Learning
Department of Computer Science, Aalto University