The distribution of dense brine under leads in sea ice is associated with convective sinking of individual plumes and near-surface mixing associated with ice-water momentum flux. The processes have been studied in the recent Lead Experiment (LeadEx) field program and previously modeled using a two-dimensional hydrostatic numerical model. In this study these processes are reexamined using a nonhydrostatic model. It is shown that nonhydrostatic effects give rise to pressure distributions which counter hydrostatic pressure gradients in the fluid. These effects are largest in sinking plume events and can be substantial when plumes are free to sink to depths of 100 m. In the presence of the Arctic halocline (typically at 30--40 m), however, vertical accelerations of convective plumes are limited spatially and temporally, and nonhydrostatic effects are relatively small. It is the purpose of this paper to demonstrate that for realistic Arctic stratification, convective circulations under leads in sea ice are predominantly hydrostatic. ¿ 1998 American Geophysical Union