Growth and steady state stages of thermohaline intrusions in the Arctic Ocean

Thermohaline intrusions are a widespread feature of the Arctic Ocean pycnoc line and may be important for the lateral transport of heat, salt, and othe r tracers. In an attempt to understand the dynamics of the intrusions, we p resent an analysis of hydrographic observations of a front north of Svalbar d. Following intrusions from profile to profile, we find that they slope up ward toward the cold, fresh side of the front. However, their slope is less than that of the background isopycnals, so that the intrusions slope betwe en horizontal and isopycnal surfaces in the "wedge" of baroclinic instabili ty. Our analysis proceeds in two stages. First, to determine what might hav e caused the initial growth of the intrusions, we compare the observed intr usion properties with predictions of an instability theory. The results sug gest that the intrusions developed as a form of double-diffusive interleavi ng, with fluxes dominated by salt fingering and additional forcing by baroc linicity. Second, to investigate the observed finite amplitude interleaving , we apply a steady state model to the observations. A key result is that d iffusive convection, not salt fingering, must be the dominant form of doubl e diffusion in order to reach steady state. This fundamental change in dyna mics is discussed in the context of adjustment from the growth stage to an eventual steady state.