114 



MAEION EXPEDITION TO DAVIS STRAIT AND BAFFIN BAY 



spriiia' Avhen iceberf>:s drift into the Gulf stream southeast of Xew- 

 foundland, then the underwater body of a berg melts faster than 

 the above part. If, on the other hand, the air is warmer than the 

 water — for example, during summer in the cold waters around the 

 Grand Banl: — the air-exposed portion of an iceberg will melt the 

 faster. But in each case account nuist be taken of the specific heat 

 of the water as compared with that of air. ]\Ielting usually pro- 

 ceeds fastest at the water line of icebergs, the engirdling furrow 

 being a common sight on bergs in the ice regions. Acceleration of 

 the rate of wastage is also affected by the size of the ice body. The 

 smaller a berg becomes the greater is the ratio between exposed sur- 

 face and mass, and therefore the faster is the rate of melting at a 

 constant temperature. Also the smaller a l;erg becomes the more 



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A Water-Washed Berg Melting Rapidly 



Figure 74.— This berg on May 9, 1921, in latitude 41° 45' N., lonj;itudt! 47° 3U' W., 

 liad been two days in the Gulf Stream south of Newfoundland : water tempera- 

 ture 63° F. Its surface is completely water washed, due to the frequent chanires 

 in equilibrium, and it has acquired a polished surface, looking much like melted 

 glass. On close inspection the berg could be seen " steaming," like an ice cake 

 on a hot summer's day. A flow of water also, due to the excessive rate if 

 melting, bathed the entire surface. (Official photograph, international ice patrol.) 



it comes under the control of the surface layers, which by virtue of 

 the'r greater warmth and more rapid motion accelerate the rate of 

 Avasting of the ice. 



The most advanced stages of melting are observed on bergs which 

 drift into the Gulf stream off the Grand Bank in summer, when 

 during the warm, calm days of late June they become furrowed by 

 hundreds of rivulets from every side. lender these conditions they 

 melt so rapidly that the plane of equilibrium is constantly altering, 

 so that the bergs roll over and over. The constant washing jxjli.shes 

 the sui'face and smoothes off all sharp prominences, and the ice that 

 reaches these subtropical surroundings fairly steams like an ice cake 

 on a hot summer's day. 



One more factor Avhich may further the jirocess of nu'lting is 

 the descent of warm aii' near icebergs. The atmosphere in the vicin- 



