41 
If the water density increase from salt rejection during sea ice formation is insufficient 
to cause deep convection and the primary mechanism instead depends upon. direct 
ocean/atmosphere contact, then the presence of sea ice has a strong negative role in addition to 
the positive role indicated in the previous paragraph for deep convection just beyond the ice 
edge. Within the pack, sea ice would prevent deep convection by the effective insulation it pro- 
vides between ocean and atmosphere (Maykut (1978) indicates that heat input to the atmosphere is 
reduced by one or two orders of magnitude in the presence of an ice cover of one meter or 
more in thickness). Hence a retreat of the ice edge in a warmer climatic period could lead to 
deep convection in regions which are currently ice covered, and an advance of the ice edge in 
colder periods would eliminate deep convection in those regions currently just seaward of the 
ice edge. 
To conclude, whether or not sea ice formation directly contributes to deep convection 
through the rejection of salt, the presence of sea ice almost certainly has an impact on the 
location of deep convection in the polar oceans and thereby presumably influences the changes in 
deep ocean circulation from one set of climatic conditions to another. 
