Change in ocean subsurface environment to suppress tropical cyclone intensification under global warming.

Ping Huang,Rong-Hui Huang,Chia Chou,I -I Lin

doi:10.1038/ncomms8188

Abstract

Tropical cyclones (TCs) are hazardous natural disasters. Because TC intensification is significantly controlled by atmosphere and ocean environments, changes in these environments may cause changes in TC intensity. Changes in surface and subsurface ocean conditions can both influence a TC's intensification. Regarding global warming, minimal exploration of the subsurface ocean has been undertaken. Here we investigate future subsurface ocean environment changes projected by 22 state-of-the-art climate models and suggest a suppressive effect of subsurface oceans on the intensification of future TCs. Under global warming, the subsurface vertical temperature profile can be sharpened in important TC regions, which may contribute to a stronger ocean coupling (cooling) effect during the intensification of future TCs. Regarding a TC, future subsurface ocean environments may be more suppressive than the existing subsurface ocean environments. This suppressive effect is not spatially uniform and may be weak in certain local areas.

Highlights

Tropical cyclones (TCs) are hazardous natural disasters
More than a decade ago, Knutson et al.[2] examined changes in the initial ocean environment due to global warming using the Coupled Model Intercomparison Project Phase 2 (CMIP2) ocean field. They reported sharpening in the ocean thermal gradient due to global warming compared with the existing environment
This finding may be explained by the global warming condition, the increasing net downward heat flux driven by increasing CO2, which initially heats the surface waters and subsequently heats the subsurface waters[2,16]

Summary

Introduction

Tropical cyclones (TCs) are hazardous natural disasters. Because TC intensification is significantly controlled by atmosphere and ocean environments, changes in these environments may cause changes in TC intensity. We investigate the changes in ocean environments (including subsurface ocean changes) under global warming[9,13,16,17] and the possible impact on future TCs. The ocean is the source of energy supply for a TC’s intensification. During a TC’s intensification, the intense TC wind inevitably mixes the preexisting and colder subsurface water with the ocean surface to reduce the sea surface temperature (SST), which is referred to as the TC-induced ocean cooling (coupling) effect (referred to as OCE)[22,23,24,25,26,31]. The SST with OCE is the actual SST encountered by a TC during its intensification (a dynamical process), the uncoupled approach does not exhibit an OCE and the SST is artificially fixed (that is, no reduction) at the pre-TC level

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Conclusion