MULTISCALE INTERACTIONS BETWEEN UPPER-OCEAN DYNAMICS AND EXTREME WEATHER

Highly nonlinear and stochastic processes such as extreme weather and oceanic mesoscale processes continue to test the limits of remote sensing and numerical modeling despite recent technological advances. Understanding the coupled feedback between the upper ocean dynamics and extreme weather benefits our ability to forecast and respond to extreme events and to make informed long-term decisions based on numerical climate models. This dissertation addresses the overarching scientific question, “How do upper ocean dynamics and extreme weather events connect the ocean and atmosphere globally and regionally, on multidecadal timescales and for episodic events?”. First, the new “moored” maximum potential intensity equation is derived, linking >26°C upper ocean heat content dynamics to the greatest intensity that tropical cyclones can attain in given oceanic and atmospheric conditions. Then, the moored maximum potential intensity equation is applied globally for ocean heat content in the upper 100 m, revealing insights into the role ocean dynamics can play in changes in extreme weather intensity and global distribution over the period 1994-2020. Finally, self-organizing maps are used to identify and characterize a particular instance of the upper ocean dynamics changing under the influence of Hurricane Ivan (2004) in the context of broader Gulf of Mexico upper ocean dynamics patterns. Findings include validation of the new “moored” potential intensity equation; a global rate of increase in potential intensity of 0.63 m s-1 per century; decrease of 7.1 m s-1 per century in the Atlantic Main Development Region; increase of more than 6.6 m s-1 per century over the Gulf Stream and Kuroshio Current likely driven by changes in upper ocean dynamics; and evidence that Hurricane Ivan (2004) in the Gulf of Mexico may have triggered a Loop Current Eddy separation event via interaction with Loop Current Frontal Eddies. These findings advance our understanding by directly relating upper ocean dynamics to tropical cyclone potential intensity and by promoting a new method to detect and describe extreme weather-upper ocean interactions. Future research will build upon these findings to explore the mechanisms by which oceanic heat fluxes drive changes in potential intensity on climate timescales and for particular events.