necessarily an objective and unbiased 

 measurement from year to year. 



Admittedly, season length is related 

 to icebergs south of 48°N, as Commander, 

 International Ice Patrol considers this 



1998 Icebergs South of 48°N by 

 Month 



of 1380 Total Icebergs 



FEB MAR APR MAY JUN JUL AUG 



Figure 6. Icebergs South of 48°N for 1998, 

 excluding growlers, bergy bits and radar targets. 



measurement in his decision on when to 

 open and close the season. Various 

 authors have discussed the appropriate 

 metric for ice season severity (Alfultis, 

 1987; Trivers, 1994; Marko, ef a/., 1994). 

 Comparing 1998 to the past five years and 

 measuring the statistics against historical 

 standards in various papers, 1998 was 

 moderate in terms of length and extreme in 

 terms of icebergs south of 48°N. Moderate 

 for season length is defined as a season 

 between 105 and 180 days. Extreme for 

 icebergs is defined as greater than 600 

 icebergs south of 48°N (Trivers, 1994, 

 Marko, era/., 1994). 



Each day during the ice season IIP 

 prepared and distributed ice bulletins at 

 0000Z and 1200Z to warn mariners of the 

 southwestern, southern, and southeastern 

 limits of ice. U. S. Coast Guard 

 Communications Area Master Station, 

 Atlantic (CAMSLANT)/NMF in 



Chesapeake, VA and Canadian Coast 

 Guard Marine Communications and Traffic 

 Service St. John's, Newfoundland/VON 



were the primary radio stations responsible 

 for the dissemination of the ice bulletins. In 

 addition, ice bulletins and safety 

 broadcasts were delivered over the 

 INMARSAT-C SafetyNET via the AOR-W 

 satellite. Other transmitting stations for the 

 bulletins included Canadian Forces 

 METOC (Meteorology and Oceanography) 

 Centre Halifax, Nova Scotia/CFH, Marine 

 Communications and Traffic Services in St. 

 Anthony, NewfoundlandA/CM, and Radio 

 Station Bracknell, UK/GFA. 



Icebergs South of 48PN Snce 1993 



1996 



1994 



1993 



500 



1000 



1500 



20CO 



Figure 7. Icebergs South of 48°N since 

 1993, excluding growlers, bergy bits and 

 radar targets. 



IIP sent 338 text bulletins in 1998. 

 IIP measures the quality and timeliness of 

 the bulletins it delivers to the mariner via 

 the SafetyNET service, as this is the 

 primary product for HP's largest customer 

 base. Of 338 total bulletins sent, 330 

 (93%) arrived on the system on time, or by 

 0000Z or 1200Z, respectively. Of the 338 

 bulletins, 330 (98%) were error-free when 

 delivered. The late deliveries mainly 

 resulted from communications system 

 failures, and the erroneous bulletins were 

 primarily a function of human error. IIP 

 also sent seven safety broadcasts. IIP 

 sends these special broadcasts whenever 

 late-breaking ice information, received 



