Analysis of 2023 Ocean Temperature Field Anomalies Using Argo Data

The Argo program, a decades-long international collaboration to establish and maintain a comprehensive ocean observation network, has revolutionized understanding of temperature structure in the world ocean. Argo’s core floats allow the structure of the world ocean’s temperature field to be spatiotemporally compared, providing a valuable resource for analyzing Earth’s climate system. Here we use a 1° × 1° × 1-month map of ocean temperatures constructed using machine learning techniques that use satellite data as predictors and Argo float temperature profiles as training data. The year 2023 was the warmest in the modern record, with mean ocean temperatures over 1°C higher than pre-industrial temperatures for the first time. Higher ocean temperatures are an important ingredient for severe weather formation, as well as increasing ocean stratification, raising sea-levels, and impacting marine ecosystems. In this project, we analyze and compare 2023’s global and regional ocean temperature fields with those of the previous 30 years, identifying key features of and contributors to 2023’s unusual temperature field. We fit local means, trends, and seasonal cycles to the 1993-2022 ocean temperature data. We then examine the impact of the mean, trend, and anomalies on the changing vertical temperature structure of the ocean, both globally and regionally. We show that the linear trend, the buildup of El Niño, and unprecedented marine heatwaves all played roles in 2023’s exceptional temperatures.