NAVEASTOCEANCEN used all of 

 these data to help bogus the 

 Labrador Sea EOTS. The highly 

 selective data collection strategy 

 improved EOTS representation of 

 the Labrador Current/North 

 Atlantic Current confluence. 



IIP encouraged NAVEASTO- 

 CEANCEN and FLE- 

 NUMOCEANCEN to take more 

 advantage of MP's drifting buoy 

 program. IIP annually deploys 6 

 to 12 TIROS Oceanographic 

 Drifters (which only measure SST) 

 in the Labrador Current. These 

 drifters remain in the IIP region for 

 up to 3 months before they are 

 entrained in the North Atlantic 

 Current. IIP deploys them during 

 iceberg reconnaissance flights, 

 monitors their performance, and 

 ensures that they are on the 

 Global Telecommunications 

 System for real-time data relay to 

 FLENUMOCEANCEN. In 1988 

 IIP began providing drift histories 

 to NAVEASTOCEANCEN so it 

 could better visualize North 

 Atlantic Current meanders and 

 eddies. The U. S. Navy has 

 funded the incremental cost to 

 have barometric sensors on some 

 IIP buoys. 



EFFECT ON NEW INPUTS ON 

 ICEBERG MELT ESTIMATES 



The replacement of existing 

 temperature and wave inputs with 

 ones that better represented the 

 environment were expected to 

 affect iceberg deterioration 

 estimates. However, from the 

 1987 IIP iceberg study (Hanson, 



1987). IIP realized that the Joterio- 

 ration estimates, derived from 

 these inputs, had to also be 

 evaluated, before assuming that 

 the modelled melt better repre- 

 sented actual melt. If the mod- 

 elled melt derived from the new 

 inputs were better, IIP would also 

 have to redefine when icebergs 

 could be deleted for reason of 

 complete melt. 



During June and July 1988, IIP 

 examined the predicted melt 

 histories of all icebergs which had 

 been sighted on or after 3 June 

 1988. This date corresponded 

 with the start of the new sea 

 height and sea period inputs from 

 FLENUMOCEANCEN. Concur- 

 rent deterioration estimates were 

 generated for each iceberg by 

 running in parallel two versions of 

 the operational deterioration 

 model. Both versions used the 

 finer gridded temperature input; 

 however, one version (VI) used 

 significant wave height and 

 primary wave period data, while 

 the other (V2) used sea height and 

 sea period. IIP used version VI 

 to predict all its operational 

 iceberg deterioration estimates for 

 the 1988 ice season. 



Versions VI and V2 were com- 

 pared with regard to the "percent 

 of melt" when icebergs were 

 deleted from the database. 

 Reasons to delete icebergs were 

 based on: a thorough aerial 

 reconnaissance of an area in 

 which an iceberg is expected to 

 have drifted, and no iceberg is 

 sighted; or when icebergs exceed 



175% of predicted melt, or 200% 

 of predicted melt for those ice- 

 bergs which set the "limits of all 

 known ice". IIP studied a sample 

 of 231 non-tabular icebergs: 71 

 small (assumed to be 60 m long); 

 102 medium (102 m long); and 58 

 large (213 m long). The maximum 

 waterline length for a reported size 

 is always assumed by the deterio- 

 ration model when an iceberg is 

 first sighted. This waterline is 

 deteriorated over time until a new 

 size is reported, which resets the 

 waterline to the maximum length 

 for that size category. 



Figure C-1 shows the scatter 

 diagrams for each iceberg size 

 category. For nearly 90% of the 

 sample, the V2 melt rate was 

 equal to or slower (better) than the 

 VI rate. A linear regression 

 analysis appeared useful in 

 describing the potential improve- 

 ment in modelling total melt for the 

 large and medium-sized icebergs; 

 the linear correlations for these 

 size categories were high; 0.97 

 and 0.86 respectively. The low 

 (0.55) correlation for the small size 

 icebergs made linear regression a 

 less reliable indicator for that 

 category. The new environmental 

 inputs appear to reduce modelling 

 error between 10% (for large 

 icebergs) and 35% (for medium 

 and small icebergs). This com- 

 parison reflects only the improve- 

 ments associated with using sea 

 height and sea period. Although 

 not measured, similar improve- 

 ment in substituting the fine for the 

 coarse resolution temperature 

 data was expected. 



83 



