The geographic coordinates that form the LAKI were hand-measured from the plots in the bulletins and 

 entered into the program created by Wright (2002). This program simply divides the area enclosed by the 

 LAKI into sub-areas, calculates the area of each sub-area and sums the results. The computation is based 

 on three assumptions: ( 1 ) that the area of interest is between the LAKI and 48°N latitude. (2) for each sub- 

 area integrated, the average latitude was used to determine the east-west distance, and (3) the land area 

 included in the calculation is negligible. Assumption (3) is required because the most common origin of 

 the LAKI is near the southern or southwestern Newfoundland coast: thus, a part of Newfoundland's 

 landmass becomes incorporated into the computed LAKI area. If the origin of the LAKI is far to the west 

 on Newfoundland, it will result in a large LAKI area, therefore minimizing the effect of the land. If the 

 origin is far to the east, the landmass enclosed by the LAKI will be small, again minimizing the error. So. 

 although a portion of Newfoundland is in the result of every calculation, this error is not significant. 



Before combining the three factors into the season severity index, each factor was normalized using the 

 mean value for the 27-year record. The LAKI area was first averaged by month for each of the years 

 (1975-2001) and then by year (all months during ice season). The mean value of the LOS and number of 

 icebergs that passed south of 48^N were also computed. Finally, all three were combined to form the 

 Normalized Season Severity Index (NSSI): 



NSSI = LAKI Area/90.234 + LOS/ 143 + S48N/702 



where LAKI area is the average area covered by the limits of all known ice during the ice season. LOS is 

 the length of season, and S48N is the iceberg population south of 48''N. The three denominators are the 

 27-year means for LAKI area. LOS. and icebergs south of 48'N. 



Discussion 



Normalized Season Severity Index (NSSI) Accuracy 



An aggregate plot of all seasonal computations (Figure 1 ) shows the characteristic behavior of the LAKI 

 area throughout a season, with a peak area in late spring. The plot was created with monthly LAKI areas 

 from 1975-2001. The ideal normal curve season would open in eariy March, peak in late May. and 

 dwindle down to a close in mid to late August. The NSSI uses an average length of season of 143 days to 

 normalize the LOS data. The average season length allows an eariy March opening and late July ending of 

 the ice season. 



57 



