Stommel transitions in shallow coastal basins

The theory of Stommel transitions is presented, and their importance discussed, for both shallow coastal systems and large-scale ocean circulation (where they are predicted to have major importance for climate change). The transitions occur in systems driven by buoyancy fluxes, and for coastal basins, involve jumps between classical and inverse states. Data are examined for Tomales Bay (California) in 1988 and suggest a Stommel transition in early autumn at a time which is consistent with the predictions of the Stommel model. The transition in Tomales Bay is primarily induced by changes in ocean and air temperatures. Stommel transitions have previously been seen in a variety of models, and laboratory simulations, but the present observation may be the first in a natural system.