bergs. Anderson (1983) and Hanson 

 (1987) describe the llPdeterioration 

 model in detail. It is the combined 

 ability of the SLAR to detect icebergs 

 in all weather and HP's computer 

 models to estimate iceberg drift and 

 deterioration which has enabled IIP 

 to reduce its ICERECDET opera- 

 tions from overlapping weekly de- 

 ployments to every other week de- 

 ployments. 



Table 1 shows the total 

 iceberg sightings reported to IIP in 

 1 989 (including resights) which were 

 in MP's operations area and away 

 from the Newfoundland coast. 

 Sightings are broken down by the 

 sighting source and iceberg size. 

 IIP ICERECDET and commercial 

 shipping were the major sources of 

 iceberg sighting reports this season. 

 AES of Canada was not able to 

 provide as many reports this season 

 as last. Appendix A lists all iceberg 

 sightings received from commercial 

 shipping, regardless of the sighting 

 location. 



Table 2 lists monthly esti- 

 mates of the total number of icebergs 

 that crossed 48°N during the vari- 

 ous reconnaissance eras: pre-ln- 

 ternational Ice Patrol, ship, aircraft 

 visual, and aircraft SLAR eras. Table 

 3 compares the estimated number 

 of icebergs crossing 48°N for each 

 month of 1 989 with the monthly mean 

 number of icebergs crossing 48°N 

 for each of the four different eras. 



During the 1989 ice year, 

 an estimated 301 icebergs drifted 

 south of 48°N latitude, compared to 

 187 during 1988. The average 

 number of icebergs drifting south of 

 48°N peryearfrom1900to 1987is 

 403 icebergs (Alfultis, 1987). IIP 

 defines those ice years with less 

 than 300 icebergs crossing 48°N as 

 light ice years ; those with 300 to 600 

 crossing 48°N as average; those 

 with 600 to 900 crossing 48°N as 

 heavy; and those with more than 

 900 crossing 48°N as extreme. 

 Thus, 1989 was an average year. 



Table 2: Total Icebergs South of 48*N - The four periods shown 

 are pre-lnternational Ice Patrol (1900-1912), ship recon- 

 naissance (1913-45), aircraft visual reconnaissance (1946-82), 

 and SLAR reconnaissance (1983-88). 



Nine satellite-tracked ocean 

 drifting buoys were deployed to 

 provide operational data for MP's 

 iceberg drift model. These buoys 

 were the same standard size drifting 

 buoys IIP has been deploying for 

 fourteen years. In addition, several 

 of these buoys were, for the first 

 time, equipped with barometric 

 pressure sensors. The U.S. Naval 

 Oceanographic Command provided 

 the funding for these barometric 

 sensors. Drift data from these buoys 

 are discussed in Appendix B. 



Prior to the start of the 1 989 

 season, 1 1 P modified its Air-deployed 

 expendable BathyThermograph 

 ( AXBT) system which was first used 

 in 1988 (Alfultis, 1988). During the 

 1989 season, IIP operationally de- 

 ployed 40 AXBT's which were pro- 

 vided by the U.S. Naval Oceano- 

 graphic Command. The AXBT 

 measures temperature with depth 

 and transmits the data back to the 

 aircraft. 



Temperature data from the 

 AXBTs were sent to the Canadian 

 tvleteorological and Oceanographic 

 Center (f^ETOC) in Halifax, Nova 

 Scotia, Canada, the U.S. Naval 

 Eastern Oceanography Center 

 (NEOC) in Norfolk, Virginia, and 

 FNOC for use as inputs into ocean 

 temperature models. IIP directly 

 benefits from its AXBT deployments 

 by having improved ocean tem- 

 perature data provided to its iceberg 

 deterioration rrrodel. To further en- 

 hance the quality of environmental 

 data used in its iceberg nnodels, IIP 

 also provided weekly drifting buoy 

 sea surface temperature (SST) and 

 drift histories and SLAR ocean fea- 

 ture analyses to METOC and NEOC 

 for use in water mass and SST 

 analyses. 



