Belle Isle and postulated the causes of observed 

 surface warming as a berg is approached. He 

 further elucidated on this warming phenomena 

 near bergs and the part it plays in deterioration 

 in a 1913 report and agam in 1927. Barnes (1927) 

 looked closely at the physical properties of bergs, 

 including the quantities of entrapped air. He 

 speculated on the causes of calving based on his 

 observations of river ice. A correlation was 

 drawn by Barnes between the internal thermal 

 stresses set up by natural conditions, i.e., the sun, 

 and the calving that resulted. He cites observa- 

 tions made in bright sunlight, concluding that the 

 penetrating rays through the clear melt water on 

 the bergs surface sets up the expansion stresses. 

 He attempted to create these stresses by using 

 thermite bombs to mduce greater calvmg. Zeusler 

 (1926) and Ricketts (1930) made quaUtative studies 

 of the melting processes supported by actual ob- 

 servations. Smith (1931) summarized the basic 

 knowledge to date, citing the various methods of 

 berg deterioration and the conditions causing 

 them. He made detailed observations of several 

 bergs deteriorating under different environmental 

 conditions. The next work of significance occurred 

 when Bidlard (1960) reported on the attempts to 

 destroy bergs. Thermite bombs were used to 

 duplicate the experiments of Barnes (1927). 

 High explosive bombs were also tried to fracture 

 the larger bergs, and the melting of a berg was 

 "hastened" by covering it with lampblack. All 

 of these methods attained only a limited degree 

 of success and were not pursued further. In 1960 

 a program was initiated to gather statistical 

 deterioiation data on bergs. Coast Guard ships 

 of opportimity were to make studies on deteriora- 

 tion when required to standby dangerous bergs 

 drifting in the shipping lanes. No information 

 as to whether or not the project gathered any useful 

 data is available, however, very few bergs in the 

 past 5 years have required a standby vessel. 



In 1964 a preliminary study was conducted by 

 Ice Patrol (Kollmeyer et al, 1964) in order to 

 gain some insight into the problem and to develop 

 the techniques required for future work. A berg 

 was observed oA'er a week's time in a relatively 

 warm air environment and \n water slightly 

 above 0° C. Unfortunately quantitative size 

 measiu-ements were of no value due to the in- 

 accuracy of radar deterinuied ranges and no 

 correlation work could be accomplished. Tlie 

 various problems encountered, particularly those 

 of size and shape measurements, lead to the use 



of more elaborate and effective equipment during 

 the 1965 study. 



Theoretical Analysis 



The deterioration parameters that can be 

 considered the most important are those which 

 contribute to the actual melting of a berg. 

 Calvmg or breakage is random, and at the 

 present time cannot be directly tied to environ- 

 mental conditions. AU forms of heat transfer 

 must be exammed. Basic prmciples of thermo- 

 dynamics indicate that to develop a workable 

 estimate and prediction system, all aspects of 

 radiative heat transfer along with detailed anal- 

 ysis of the small scale phenomena of the fluid 

 boundary layers must be investigated. 



The intent herein is not to present an all en- 

 compassing document of heat transfer to icebergs, 

 but to outline an intensive study that will ul- 

 timately lead to accurate deterioration prediction 

 models. 



The heat budget of an iceberg can be described 

 as follows: 



Net heat added = heat required to raise a berg's 

 temperature. In this treatment, complete melt- 

 ing is the primary concern, therefore the net 

 heat added will be considered as that heat used 

 to raise a berg's temperature to 0° C. and to 

 melt the ice (heat of fusion). 



Q,= direct incoming solar radiation 



Qr = solar radiation reflected from a berg's 



surface 

 ^o=convective-conductive heat from the air 

 Q„=convective-conductive heat from the 

 water 

 Qaa,r=air and water radiative transfer to berg 

 Qir= iceberg back radiation 

 A quantitative look must be given to the heat 

 budget equation of a berg to determine which 

 terms are important and which ones can be 

 dropped. A hypothetical berg will be used for 

 this purpose. Deterioration data based on years 

 of experience will be drawn from Ice Patrol 

 (Lenczyk 1964), as shown in table IC. Listed 

 therein are rules of thumb used to predict the 

 life of various sized bergs in several different 

 water temperature envu-onments. These are gross 

 figures and will be utilized only to show the im- 

 portance of each heat transfer process. The 

 selected figures to be used are 2.2° C. water tem- 



42 



