stability index of centimeters of potential ice thickness per meter of 

 convection is' expressed as a percentage. A high percentage denotes 

 relatively high stability, since the vertical stratification of the 

 water mass is great when a large increase in potential ice thickness 

 accompanies a small Increase in depth of convection (section B 3)* 

 Sim:Llarlyjj a low percentage indicates relatively lovr stability. 



Figure h shows the stability index for 1951 as derived from figures 

 1 and 3» A feature of the chart is the wide range of index levels from 

 below zero to over 26 (an index below zero denotes so-<:alled negative 

 ice potential or lack of ice formation after the fixed heat loss has 

 taken place )« The greatest stability is found in the area north and 

 northeast of Mackenzie Bay, where the runoff from the Mackenzie River 

 is an influenceo A second small area of high stability to the south 

 of Banks Island may also represent runoff. Two Interesting areas of 

 relatively low stability exist near Banks Island* To the southvfest 

 of the island in the same area as the low potential ice thicknesses 

 in figure 2, the stability is low. This area is shown by good data 

 to be definitely cut off on the north at about 73°N« It thus farms 

 a small pocket of unstable water between the stable waters of the 

 runoff area to the southfrjest and the area along the southern coast 

 of Banks Island « A second very small area of low stability of unknown 

 origin is found in the southern part of Amundsen Gulf, centered at 120°W» 



5. Areas with Similar Ice Potential and Stability 



The charts discussed above, figures 1 through kg share to some ex- 

 tent a common difficulty in ready ans'lysis. As a summJjry and combina- 

 tion of the above figures, figure 5 is presented to indicate the various 

 areas in the Beaufort Sea and adjacent waters within which ice potentials 

 and stability index readings are slmilor« In the figure the locations 

 of the areas and their relative size are immediately apparent. Shapes 

 and sizes of the areas are approximate* 



The areas in figure 5 are determined by classifying the main areas 

 of figures 2 and k into six tilasses by arbitrarily dividing the potential 

 ice thicknesses into two categories, less than litO cm, and greater than 

 lliO cm. In addition, the stability index is divided into three categories, 

 less than 8 percent, from 8 to 16 percent, and greater than l6 percent. 

 These categories are referred to as low or small, moderate, and high 

 or greato Although there are six possible classes, only four are found 

 to existo 



Area A in figure 5 is characterized by low ice potential and low 

 stability. In this region the convective depths as shoxm in figure 3 

 are so great that in winter the thermohaline mixing reaches to the 

 bottom in shallofrr waters, while the total amount of ice formed by the 

 given heat loss is smalle 



ifi area B of figure 5 "the potcnitial ice thickness is great, and the 

 stability is low. This area includes the cold water of the central Arctic, 

 which has low stability because the surface layer remains close to the 

 freezing poirxt during the summer , The area has two small offshoots toward 

 the shore, one between areas A and C, end the other between areas C and D. 



