A Structural Front Over the Continental Shelf of the Eastern Bering Sea

Conductivity and temperature vs. depth (CTD) and expendable bathythermograph (XBT) data taken during the ice-free seasons of 1975-1977 define a structural front paralleling the 50-m isobath. This front forms a narrow transition separating a well-mixed coastal domain from a two-layered central shelf domain. In early spring, prior to frontogenesis, temperature and salinity are continuous across the 50-m isobath. Thus, the front does not result from the confluence of water masses; rather, the front permits the evolution of different water masses following frontogenesis. The changing balance between buoyant energy input and tidal stirring determines the frontal location, and the frontal width correlates with bottom slope. The front is similar to those reported around the British Isles; but in the Bering Sea, the salinity distribution is important, the ice cover influences the seasonal evolution of the hydrographic structure, and the geostrophic (baroclinic) speed differences across the front are small (< 2 cm sec super(-) super(1) ). The authors hypothesize that frontogenesis depends critically upon positive feedback between stratification and mixing.