WHOI PO

The circulation within marginal seas subject to periodic winds, and their exchange

with the open ocean, are explored using idealized numerical models and theory. This is motivated

by the strong seasonal cycle in winds over the Nordic Seas and the exchange with the subpolar

North Atlantic Ocean through the Denmark Strait and Faroe Bank Channel, although the analysis

is general in nature and relevant to other marginal seas. Two distinct regimes are identified: an

interior with closed 𝑓 /ℎ contours and a shallow shelf region that connects to the open ocean. The

interior develops a strong oscillating along-topography circulation with weaker ageostrophic radial

flows. The relative importance of the bottom Ekman layer and interior ageostrophic flows depends

only on 𝜔ℎ/𝐶, where 𝜔 is the forcing frequency, ℎ is the bottom depth, and 𝐶 is a linear bottom

drag coefficient. The dynamics on the shelf are controlled by the frictional decay of coastal waves

over an along-shelf scale 𝐿 = 𝑓 𝐿𝑠  H𝑠 /𝐶, where 𝑓 is the Coriolis parameter, and 𝐿𝑠 and 𝐻𝑠 are

the shelf width and depth. For 𝐿 much less than the perimeter of the basin, the surface Ekman

transport is provided primarily by overturning within the marginal sea and there is little exchange

with the open ocean. For 𝐿 on the order of the basin perimeter or larger, most of the Ekman

transport is provided from outside the marginal sea. There is also an opposite exchange through

the deep part of the strait, as required to conserve mass within the marginal sea. This demonstrates

a direct connection between the dynamics of coastal waves on the shelf and the exchange of deep

waters through the strait, some of which is derived from below sill depth.