Appendix C 



Analysis of Limit-Setting Icebergs 



CDR Ross L Tuxhorn and MST3 Tristan T. Krein 



Introduction 



Data Collection 



International Ice Patrol's mission is to iden- 

 tify the Limit of All Known Ice (LAKI) and to trans- 

 mit this information to mariners at sea. During the 

 ice season, the key element of IIP operations is to 

 conduct reconnaissance patrols to determine the 

 location of icebergs that establish the LAKI. 



The LAKI is based on all known iceberg 

 and sea ice information and represents the extent 

 of iceberg danger in the vicinity of the Grand Banks 

 of Newfoundland. From Newfoundland, the line 

 marks the southwestern, southern, and southeast- 

 ern limits of the iceberg region, and ends at an 

 intersection point with latitude 52°N. Over the last 

 twenty years, at its extremes, the LAKI has ex- 

 tended in the northwestern Atlantic Ocean as far 

 south as latitude 39°N, and in the east to longi- 

 tude 37°W. In 1995, the southernmost iceberg 

 was sighted at 39°59'N and the easternmost ice- 

 berg was sighted at 43°01'W. 



International Ice Patrol in recent years has 

 collected data to learn more about the icebergs 

 that establish the LAKI. In 1994, the sources of 

 all sightings south of 45°N were determined. The 

 analysis of this data indicated the large relative 

 contribution of sightings from IIP reconnaissance 

 flights in the area near the limits. This year, the 

 study continued and went further to investigate the 

 attributes of the individual icebergs that set the 

 limits of all known ice. 



This information pertaining to the limit-set- 

 ting icebergs is important as a measure of effec- 

 tiveness of HP's surveillance efforts in locating the 

 iceberg hazard. It is MP's goal to continuously 

 improve its mission performance by effectively lo- 

 cating the icebergs that constitute the LAKI and 

 promptly providing this information to ships to bet- 

 ter enable them to avoid encountering icebergs. 



Limit-setting icebergs are those icebergs 

 that form the vertices of the LAKI. They are differ- 

 entiated as eastern, southern, and western limit- 

 setting icebergs by the side of the LAKI "polygon" 

 that they occur at. For the majority of cases in 

 this study, the three categories of icebergs were 

 distinct populations. The few exceptions occurred 

 when icebergs drifted from the southern limit to 

 the eastern limit. In those instances the iceberg's 

 designation was changed accordingly 



Data on the limit-setting icebergs was gath- 

 ered daily from the output of the Iceberg Data 

 Management and Prediction System (Df^PS). 

 Icebergs were recruited as limit-setters either from 

 the 1200Z Ice Bulletin list of "icebergs not in area 

 of many bergs" or from iceberg sightings by the 

 various sources at or near the LAKI. Each day, 

 the icebergs in the limit-setter database were ac- 

 counted for. The attributes of those icebergs were 

 checked to ascertain any resights or deletions, and 

 any changes were recorded. The following infor- 

 mation was determined for each of the designated 

 limit-setting icebergs: 



1. DMPS iceberg number. 



2. Days on plot in DMPS model. 



3. Days as a limit-setting iceberg. 



4. Source of sighting when entered in limit- 

 setter data base, and any subsequent 

 resighting source. 



5. Location on LAKI - W, S, E. 



6. Method of deletion: Collection of data 

 on a given limit-setting iceberg 

 ended when it was deleted from DMPS 

 by standard IIP criteria There 

 are two reasons why IIP removes an 

 iceberg from DMPS: 



a. The iceberg deterioration model 

 predicted the iceberg has melted 

 (Anderson, 1983) 



45 



