l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I28 



of the warm water from the region of St. Michael goes to the north- 

 west toward Wrangell Island. 



The extremes of temperature experienced by the marine inverte- 

 brate animals at Barrow below a depth of 50 feet during the summer 

 of 1948 and the period from June 30, 1949, to September i, 1950, 

 ranged from a high of 4.1° C. to a low of —1.8° C. recorded, re- 

 spectively, on September 6, 1949, and July 27, 1950. The variation in 

 temperature at the surface is a few degrees more than that of deeper 

 water. The highest surface temperature in 1948 was 7.0° C. on 

 August 17, but that year floating ice was always present in greater 

 or lesser amounts. In 1949, a surface temperature of 7.0° C. was 

 recorded on August 11, 12, 13, 14, and 16; the highest that year was 

 7.2° C. on August 17. These temperatures were taken at approxi- 

 mately 5 p.m.; the morning temperature on these days was 6.7° C. 

 These dates were just after the sun began dipping below the horizon. 

 The higher temperatures were very fleeting, usually lasting only a 

 few hours. 



The coldest temperature recorded, taken through a hole in the ice, 

 was —2.1° C. from November 13, 1949, until March 22, 1950. From 

 March 23, 1950, to April 16 the temperature was —1.9° C. ; on May 

 30, 1950, it reached —1.5° C, and from then until the time the ice 

 went out it gradually warmed to 0.5° C. In 1949 the surface tempera- 

 ture jumped from —0.4° C. on July 30 to 4.5° C. on July 31. The ice 

 had been gone since the night of July 19. 



As explained under the discussion of the natural history of marine 

 invertebrates, there are few animals that are affected by surface tem- 

 peratures. In general it can be said that the extremes to which the 

 invertebrate animals in the vicinity of Point Barrow are subjected are 

 from — 1.8° to 4.0° C, as shown by the writer's records for an entire 

 year and for three summers. This is a range of less than 6.0° C. The 

 following table gives the average monthly records for the time that 

 this investigation was carried on. The twice-daily records for this 

 period were considered too extensive for inclusion in this report, 

 especially since, with the possible exception of some planktonic forms, 

 surface temperature has little effect on the invertebrates of the region. 



Table 2 gives the extremes of temperature during the same period 

 covered by table i. 



While the temperature may be 7° C. at the surface, 10 feet down 

 it will be at least 3° or 4° colder. Time and facilities did not permit 

 the routine taking of temperatures at the two most useful depths — 

 50 feet, and on the surface of the bottom. 



The frozen ground (permafrost) extends approximately 1,000 feet 



