Compounding impact of severe weather events fuels marine heatwave in the coastal ocean

B Dzwonkowski,G Lockridge,K Park,J Coogan,T Lee,S Fournier

doi:10.1038/s41467-020-18339-2

Abstract

Exposure to extreme events is a major concern in coastal regions where growing human populations and stressed natural ecosystems are at significant risk to such phenomena. However, the complex sequence of processes that transform an event from notable to extreme can be challenging to identify and hence, limit forecast abilities. Here, we show an extreme heat content event (i.e., a marine heatwave) in coastal waters of the northern Gulf of Mexico resulted from compounding effects of a tropical storm followed by an atmospheric heatwave. This newly identified process of generating extreme ocean temperatures occurred prior to landfall of Hurricane Michael during October of 2018 and, as critical contributor to storm intensity, likely contributed to the subsequent extreme hurricane. This pattern of compounding processes will also exacerbate other environmental problems in temperature-sensitive ecosystems (e.g., coral bleaching, hypoxia) and is expected to have expanding impacts under global warming predictions.

Highlights

Exposure to extreme events is a major concern in coastal regions where growing human populations and stressed natural ecosystems are at significant risk to such phenomena
Provide a unique view of shelf heat content and its potential to have contributed to the intensification of Hurricane Michael (Fig. 2a)
The heat content only dropped by ~0.5 °C over the 3–4 days when Michael transited across the shelf, leaving the conditions well above the 26 °C threshold typically considered conducive for storm intensification[9]

Summary

Introduction

Exposure to extreme events is a major concern in coastal regions where growing human populations and stressed natural ecosystems are at significant risk to such phenomena. We show an extreme heat content event (i.e., a marine heatwave) in coastal waters of the northern Gulf of Mexico resulted from compounding effects of a tropical storm followed by an atmospheric heatwave This newly identified process of generating extreme ocean temperatures occurred prior to landfall of Hurricane Michael during October of 2018 and, as critical contributor to storm intensity, likely contributed to the subsequent extreme hurricane. While the previous studies showed connections between the shelf thermal structure and coastal storm intensification, the threats associated with the amplification of storms making landfall necessitate a broader understanding of processes by which shelf heat content can be pushed to extreme levels This critical gap in understanding is in large part due to the lack of observational data during extreme events, which by their definition are rare.

Methods

Results

Conclusion