Identifying Water Column Heat Anomalies in the Gulf of Mexico: 2023-2024

Globally warming sea subsurface temperatures can cause metabolic stress in many marine organisms. The Office of Ocean Exploration at the National Oceanic and Atmospheric Administration and its partners identify new species inhabiting the deep sea each year, many of which may be sensitive to extreme marine heat. Understanding patterns and identifying incidents of heat events that impact vulnerable species necessitates systematic monitoring of water column temperatures. While satellite-derived data provides ocean-scale coverage of sea surface temperature, observing sea subsurface temperature requires the use of in-situ observation platforms such as autonomously profiling Argo floats. This project identifies and characterizes subsurface marine heat anomalies in 2023 and 2024 using 385 profiles taken by the Argo array in the Gulf of Mexico based on a 2005-2017 climatology. Warm temperature anomalies reached 2.7 ± 0.66 ˚C between 60-400 m deep and converged to <0.1 ˚C at 1,500 m deep. When the data were disaggregated by month, most months showed warmer average temperatures than the climatology period aside from cool anomalies in April and October 2023 between 80-800 m. Disaggregated by season, winter and summer 2023 exhibited more intense warm anomalies than spring and autumn, possibly due to wind mixing, while all seasons showed similar anomaly intensity in 2024. Using this methodology, we have begun to explore how these heat anomalies affect subsurface oxygen concentrations which influence primary production and physiological stress levels in marine organisms. Building this knowledge of in-situtemperature and oxygen conditions can inform future research on the impact of an evolving marine environment on deep-sea organisms.