Offshore wind farms and upwelling

Large offshore wind farms will create a wake in wind speed behind the wind farm. If the wake has the same size as the dynamical scales of the ocean, general theoretical arguments suggest that the wake will create substantial up- and down-welling behind the wind farm (i.e. downwind). Here we will present idealized model studies that describes this process, the focus is mainly on the short term dynamics (say up to a few days), but possible long term (say up to weeks/month) dynamical effects will also be discussed. We find that the dynamical impact on the ocean is surprisingly large. The dynamical reason is that the ocean is forced with unnatural strong direct forcing of total vorticity through the horizontal gradient in the forcing; this creates an up- down-welling dipole that will create ocean currents, and also induce a self-advection dipole structure. The long term impact of the wind farm on the ocean probably requires detailed model studies with realistic conditions; however, based on the idealized experiment we provide some general predictions of the system.