The physics of turbulence over antarctic leads and polynyas and its parameterization: A joint study using observations, LES and a micro-/mesoscale model
Responsible: Björn Witha
Project type: Joint project with the ​Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Christof Lüpkes (funded by ​DFG)
Duration: 01/03/2007-31/12/2009

Web page of the joint project:​BOLE

In regions with large sea ice concentrations there are always open water areas called leads or polynyas depending on their shape. The length of leads varies between a few kilometres and tens of kilometres and their width ranges from several meters to kilometres. The strong sensible and latent heat fluxes above such areas can trigger convection which significantly modifies the atmospheric boundary layer (ABL). For this reason leads are supposed to have a large influence on the energy exchange between the polar ocean and the atmosphere.

The goals of this project are to get a better understanding of the still not well understood effects of leads and polynyas on the boundary layer turbulence and to clarify their importance for the energy budget and structure of the ABL.
Results of the LES model PALM and new helicopter based observations of turbulence over leads will be used to (further) develop parameterizations of the lead effect which can be used in models with different grid sizes ranging from microscale non eddy resolving models to weather forecast and regional climate models. The parameterizations are tested in the nonhydrostatic model METRAS.

An animation of a flow over an ice lead can be found in our gallery.