Nonhydrostatic haline convection under leads in ... - Wiley Online Library

3 downloads 0 Views 3MB Size Report
Feb 15, 1998 - James H. Morison. Polar Science ... been conducted by Kozo [1983], Smith and Morison [1993], and. Kantha [1995]. .... k s - BsV4S -Jr- Qs (6).
JOURNAL OF GEOPHYSICAL

RESEARCH,

VOL. 103, NO. C2, PAGES 3233-3247, FEBRUARY

15, 1998

Nonhydrostatic haline convectionunder leads in sea ice David

C. Smith IV

EnvironmentalFluid DynamicsProgram,Mechanicaland AerospaceEngineeringDepartment Arizona State University,Tempe

James H. Morison Polar ScienceCenter,Applied PhysicsLaboratory,Universityof Washington,Seattle Abstract.

The distribution

of dense brine under leads in sea ice is associated with

convectivesinkingof individualplumesand near-surfacemixingassociated with ice-water momentumflux. The processes havebeen studiedin the recentLead Experiment (LeadEx) field programand previouslymodeledusinga two-dimensional hydrostatic numericalmodel. In this studytheseprocesses are reexaminedusinga nonhydrostatic model. It is shownthat nonhydrostatic effectsgive rise to pressuredistributionswhich counterhydrostaticpressuregradientsin the fluid. These effectsare largestin sinking plume eventsand can be substantialwhen plumesare free to sink to depthsof 100 m. In the presenceof the Arctic halocline(typicallyat 30-40 m), however,verticalaccelerations of convectiveplumesare limited spatiallyand temporally,and nonhydrostatic effectsare relativelysmall.It is the purposeof this paper to demonstratethat for realisticArctic stratification,convectivecirculationsunder leadsin sea ice are predominantlyhydrostatic. 1.

Introduction

Leadsare small-scale (