Interim Report 



Iceberg Deterioration 



by 



Ronald C. Kollmeyer, U.S. Coast Guard 



Introduction 



The problem of iceberg deterioration is an 

 intimate part of iceberg forecasting. The ability 

 of commander, International Ice Patrol to make 

 accurate predictions of the positions of icebergs 

 that may menace the shipping lanes depends not 

 only on reliable drift data but dependable esti- 

 mates of life expectancy as well. At present, the 

 only way to determine when a berg can be dropped 

 from consideration is by direct observation of its 

 progressive reduction in size. Hence, as tech- 

 niques of drift prediction are perfected and 

 scouting for position becomes less necessary, there 

 must be a corresponding increased ability to 

 predict deterioration rate, if any substantial 

 saving in man hours, fuel and equipment are to be 

 safely realized. This will require perfection of the 

 techniques to the point where accurate automatic 

 downgrading of specific bergs can be made with 

 complete confidence without actually viewing 

 them. 



Some attention has been given to the problem 

 of iceberg deterioration since 1912, however no 

 quantitative work was ever accomplished which 

 would lead to reasonably precise predictions. 



The idealized solution to the problem calls for 

 a detailed examination of the heat budget of an 

 iceberg. Basically, the heat transfer into a berg 

 causes melting, the rate of which is dependent 

 upon many factors. Coupled with the melting is 

 the phenomena of calving or the breaking off of 

 ice pieces. The calving problem complicates 

 prediction schemes because of its randomness in 

 both quantity and frequency. Mass distribution, 

 prominence configuration and existing cracks all 

 play a part in calvnng thus rendering the calving 

 problem unpredictable under any conditions. 



Detailed heat transfer studies can be accom- 

 plished for small areas of ice surface, but difficulty 

 arises when these studies are extended to the entire 

 surface of an iceberg. Unequal heat transfer, 

 caused by unequal temperature distributions and 



turbulence, prevents the extension of mathemati- 

 cal relationships to actual conditions and makes 

 modeling difficult. The underwater configuration 

 also plays a major part in the deterioration by 

 presenting varying siu"face areas for a given mass. 

 These shapes can only be speculated on until 

 actual observations are made. In the interim 

 gross conclusions must be drawn to categorize 

 the subsurface shapes and sizes into groups, 

 sub-groups and deterioration types. These types 

 reflect the mass to surface area ratios which 

 affect the heat transfer and melting rates. At 

 present only the portion of the berg above the 

 water can be classified by deterioration type. 

 Bergs of the drydocked or pinnacle shapes tend 

 to have low mass to surface area ratios while a 

 blocky or spherical berg tends to have a larger 

 ratio. While these ratios play a role in grouping 

 surface deterioration types, no consideration can 

 be given to the underwater portion because of the 

 lack of ability to determine the underwater 

 configuration. 



The logical direction for research in berg de- 

 terioration should be along statistical lines. Basic 

 deterioration parameters must be measured along 

 with quantitative mass size changes in an attempt 

 to correlate the data and develop an effective 

 method for predicting deterioration rates. This 

 prediction method must be based on easily ob- 

 tainable parameters such as air and water tem- 

 peratures, wind velocities, sea state, berg size, 

 and configiu-ation. 



Previous Work 



In the past no really quantitative work has 

 been performed on berg deterioration. Much is 

 available in the descriptive field of berg disin- 

 tegration but basic correlative data along with 

 mass changes are not available. 



Barnes (1912) one of the early observers of 

 bergs, made water temperature measurements in 

 the vicinity of icebergs in and near the Strait of 



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