ABSTRACT

Influenced by air-sea heat exchange, rainfall, and evaporation, the buoyancy of the ocean?s uppermost layer can impact the overturning oceanic circulation. Winds above the ocean surface can generate currents and promote mixing. The combined effects of wind and buoyancy on the ocean are ultimately felt throughout the entire ocean. In response to the changing ocean conditions (especially, the sea surface temperature or SST), atmospheric circulations can arise to govern patterns of clouds and rain, which in turn impact the wind and buoyancy forcings on the ocean. To this end, mechanisms involving buoyancy and winds at the air-sea interface are critical in establishing the timescales, patterns, and amplitudes of many climate variations we observe and simulate in climate models. Yet, complete understanding of these mechanisms remains elusive due to sparse ocean observations and complicated dynamics. The research will decompose the relative effects of winds versus buoyancy forcing using climate model experiments, with emphasis on two features expected to substantially change in a future climate, namely the surface temperature and the Atlantic Meridional Overturning Circulation (AMOC).

In particular, many open questions remain about the importance of winds versus buoyancy forcing as pathways through which the atmosphere communicates intrinsic and externally forced variations to the ocean. Addressing these questions is made more difficult by a wide gap in the model hierarchy, between fully coupled models with a complete dynamical representation of both the ocean and atmosphere and models that represent the ocean as a motionless slab that is only thermally coupled to the atmosphere. This work will be implemented by closing said gap in the model hierarchy via leveraging a mechanically decoupled (MD) version of a climate model, which isolates variations in the ocean circulation that are driven solely by buoyancy from the wind-driven variability captured by fully coupled models. With the MD as an intermediate step between fully coupled and slab ocean models, a clearer mechanistic understanding of the drivers of climate variations is possible. These three model versions will be used together to identify the relative roles of buoyancy and wind variations in driving intrinsic SST variability, anthropogenic trends in surface temperature, and intrinsic and anthropogenically forced AMOC variations.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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