CANADIAN FISHERIES EXPEDITION, 1914-15 



245 



8. IXFLUEXCE OF MELTlXG ICE UPON THE MOVEMENTS OF SEA- 



W»ATER. 



One of the strongest and most effective causes of ocean currents and hydro- 

 graphical changes is, as Prof. Otto Pettersson' has shown, the melting of ice. If a piece 

 of ice be placed in a tank of sea-water, the water will soon exhibit very strong and 

 distinct current movements, the melting of the ice also occasioning marked alterations 

 in the temperature, salinity, and specific gravity of the water. 



Professor Pettersson found by his experiments that the melting of the ice gave rise 

 to three currents in the water, a cold surface current of low salinity proceeding in a 

 direction away from the ice; below this a warm salt current moving toward the ice; and 

 finally a cold salt bottom ciirrent away from the ice again. 



I have also carried out some experiments of this nature with melting ice in sea- 

 water. A glass-walled tank, 350 cm. long, 40 cm. broad, and 40 cm. deep, was filled 

 with sea-water to a height of 35 cm. In one end of the tank was then placed a rectan- 

 gular piece of ice measuring 61 cm. length, by 40 cm. width, and 23 cm. thickness. 

 At the other end of the tank a current of water was introduced at a temperature of 

 8° C. and with a salinity of 30 per cent, the inflow taking place at the rate of 12 cm. 

 per second with a corresponding outflow from the surface so as to maintain a con- 



/C£: 



Fig. 29. — Ice melting experiment. 



staiit level. The outflow took place in a separate compartment of the tank, 75 cm. long, 

 divided off from the remaining, consequently 275 cm. long by a partition 25 cm. high, 

 so as to leave free communication between both portions of the tank through the space 

 of 10 cm. above the partition, vide fig. 29. The object of this inflow arrangement was 

 to procure stationary conditions in the tank. The system thus arrived at. by the way, 

 is very much like the conditions prevalent in the gulf of St. Lawrence, which commu- 

 nicates with the ocean through Cabot strait. 



The block of ice was placed in the tank at 11 a.m., and immediately commenced 

 to melt at the rate of 0-80 cm.^ per second. As the sun-omiding water was brought into 

 circulation, the rate of melting increased, so that by 12 o'clock it was 1-24 cm.^ per 



1 O. Pettersson. On the influence of ice-melting upon oceanic conditions, 

 grafisk-bio'.ogiska liommissionens skrifter II. Gothenburg, 1905. 



Svenska hydro- 



