<i>In-situ</i> oceanographic observations of tropical cyclones from instrumented sea turtles

Abstract Tropical cyclones draw their energy from warm seas and, all other things being equal, the warmer the ocean surface, the more intense the storm. However, tropical cyclones also cool the surface ocean primarily by mixing it with deeper, cooler waters. The ‘cold wake’ acts as a negative feedback–reducing the storm’s intensity. Our ability to incorporate this information in forecasts is limited by a lack of ocean observations within tropical cyclones, particularly in shallow seas inaccessible to autonomous Argo floats. Here, we show observations of the response of the upper ocean to five tropical storms obtained from sea turtles instrumented with oceanographic sensors. The turtle observations captured key ocean processes, such as mixing induced ocean cooling, that are important for forecasting. In comparison, an ocean reanalysis system that blends existing ocean observations but notably, not the turtle observations, with an numerical ocean model, fails to capture many of the processes responsible for the surface ocean cooling. Having shown the utility of the observations for ocean-tropical cyclone interaction studies, we discuss the role that a turtle based observing system could play in monitoring and forecasting tropical cyclones worldwide.