The Arctic Ocean thermohaline stratification frequently exhibits a staircase structure overlying the Atlantic Water Layer that can be attributed to the diffusive form of double‐diffusive convection. The staircase consists of multiple layers of O(1) m in thickness separated by sharp interfaces, across which temperature and salinity change abruptly. Through a detailed analysis of Ice‐Tethered Profiler measurements from 2004 to 2013, the double‐diffusive staircase structure is characterized across the entire Arctic Ocean. We demonstrate how the large‐scale Arctic Ocean circulation influences the small‐scale staircase properties. These staircase properties (layer thicknesses and temperature and salinity jumps across interfaces) are examined in relation to a bulk vertical density ratio spanning the staircase stratification. We show that the Lomonosov Ridge serves as an approximate boundary between regions of low density ratio (approximately 3–4) on the Eurasian side and higher density ratio (approximately 6–7) on the Canadian side. We find that the Eurasian Basin staircase is characterized by fewer, thinner layers than that in the Canadian Basin, although the margins of all basins are characterized by relatively thin layers and the absence of a well‐defined staircase. A double‐diffusive 4/3 flux law parametrization is used to estimate vertical heat fluxes in the Canadian Basin to be O(0.1) W m−2. It is shown that the 4/3 flux law may not be an appropriate representation of heat fluxes through the Eurasian Basin staircase. Here molecular heat fluxes are estimated to be between O(0.01) and O(0.1) W m−2. However, many uncertainties remain about the exact nature of these fluxes.

The strength of mixing in the Arctic Ocean is an important control on the ability of heat in the ocean interior to penetrate the stratified upper ocean below the sea ice (D'Asaro & Morison, 1992). However, our understanding of mixing in the Arctic Ocean is arguably the most limited of all regions of the world ocean. As a consequence, the spatiotemporal variability of heat loss from inflowing Atlantic and Pacific waters is not well known (e.g., Lenn et al., 2009;Lincoln et al., 2016). In particular, observations of mixing in the Arctic Ocean are scarce, with direct (i.e., microstructure) inferences of ocean mixing being limited both temporally and geographically. In large-scale studies of ocean mixing rates inferred using indirect methods (

Double‐diffusive stratification in the ocean is characterized by staircase structures consisting of mixed layers separated by high‐gradient interfaces in temperature and salinity. These double‐diffusive layers, which flux heat vertically, are observed over a vast region of the Arctic Ocean at the top boundary of the relatively warm and salty Atlantic water layer. In one formalism for the origin of double‐diffusive layers, staircase formation arises when a heat source is applied at the base of water that is stably stratified in salinity. This framework is extended to consider the effect of intermittent shear‐driven turbulence on diffusive‐convective staircase formation. One‐dimensional numerical model results indicate that there is a critical level of intermittent turbulence above which a staircase cannot form. This is framed in terms of a critical diffusivity ratio (ratio of effective salinity diffusivity to effective thermal diffusivity) that cannot be exceeded for a staircase to persist. This critical ratio is not a universal constant but rather differs for each staircase. Model results further indicate that layer thicknesses decrease with height in a staircase, with the variation in thickness over a staircase being more pronounced in the presence of intermittent turbulence. Finally, results suggest that increased diffusivity ratios lead to decreased heat fluxes across interfaces; if a staircase is subject to intermittent turbulence levels (below the critical level), vertical heat fluxes will be smaller than in the absence of shear‐driven turbulence. Findings are related to double‐diffusive staircases, and associated heat fluxes, in the weakly turbulent Arctic Ocean.