Discussion 



The rate at which icebergs are resighted 

 strongly influences the measures of ice sea- 

 son severity. If icebergs had been resighted at 

 the same rate in 1993 as they had been in 

 1992, the total number of icebergs entered 

 into the system would have reached 5250, an 

 increase of 850. While the icebergs crossing 

 48N cannot be directly estimated from this 

 process, the season would have probably 

 surpassed 1 984 (2202 icebergs) as the heavi- 

 est on record. 



Otherfactors also influence the iceberg 

 totals in the study years. In 1 993, all reported 

 iceberg sightings from reconnaissance were 

 used. Before the DMPS system representa- 

 tive icebergs from the reports would be en- 

 tered into the model, reducing the number of 

 icebergs added. No effort has been made 

 heretoinvestigatethe relative reconnaissance 

 level in each year or to normalize the iceberg 

 statistics for the use of new sensors or tactics. 



The change in computer systems al- 

 lows IIP to more accurately correlate new 

 sightings with old icebergs, and more effec- 

 tively determine if icebergs were previously 

 detected. This change is the most recent in 

 the factors affecting MP's annual iceberg count 

 (See Anderson, 1993, this volume, for past 

 changes). Users of these data must consider 

 these technological changes as a part of any 

 analysis. 



References 



Murphy, D.L. and I. Anderson, 1985. An 

 Evaluation of the International Ice Patrol Drift 

 Model. Appendix D of Report of the Interna- 

 tional Ice Patrol in the North Atlantic. Bulletin 

 No. 71. CG-1 88-40. International Ice Patrol, 

 Avery Point, Groton, CT. 90 pp. 



90 



