Abstract
Midlatitude gyres in the ocean are large scale horizontal circulations
that are intensified on the western boundary of the ocean, giving rise
to currents such as the Gulf Stream. The physical mechanism underlying
gyres is widely recognised to involve the curl of the wind stress, which
injects potential vorticity into the upper ocean. However, model results
have highlighted the role of surface buoyancy fluxes (principally
heating and cooling of the ocean surface) in driving circulation and
enhancing gyre variability. Here we present results from numerical
simulations in the fully turbulent regime which show that gyre-like
circulation can be driven by surface buoyancy fluxes alone. We explore
this phenomenon through a combination of modelling and linear theory to
highlight that the transport of ocean gyres depends upon surface
buoyancy fluxes as well as wind stress. Thus, the strength of gyres may
be influenced by surface warming in response to climate change.