NO. 9 MARINE INVERTEBRATES, ALASKA — MacGINITIE 9 



Lagoon is Smith Bay, into which flows the Ikpikpuk River. Teshek- 

 puk Lake, the largest lake on the northern slope, empties into the 

 same bay through a channel, the mouth of which joins the delta of 

 the Ikpikpuk. These rivers are important to the marine life off Point 

 Barrow for they affect the salinity of the water and carry to the ocean 

 organic material that supplies some of the detritus on the bottom 

 offshore. 



As has been mentioned under "Climate," the average annual rain- 

 fall of the northern slope is only about 4 inches, so the runoff is not 

 great. Because of the relatively slight variation in elevation, these 

 rivers meander amazingly and the currents are slow. Occasionally 

 one lake may break through into another, and the resulting flow of 

 water thaws the permafrost and sometimes cuts a channel several feet 

 deep. 



The discharge from Elson Lagoon has more effect on the ocean 

 water near Point Barrow than that from any other source. There are 

 several reasons for this : ( i ) The fresh water from the rivers flow- 

 ing into Elson Lagoon through Admiralty Bay and Dease Inlet is of 

 considerable volume. (2) The lagoon is large and quite shallow. Ref- 

 erence to U. S. Coast and Geodetic Survey map 9495 shows that 

 Elson Lagoon, Dease Inlet, and Admiralty Bay together form a body 

 of water 90 square miles in area, and nowhere is the depth more than 

 12 feet. The bottom is a blue mud, which is stirred up by wind waves, 

 and carried in large quantities into the sea, sometimes coloring it for 

 miles alongshore and offshore. (3) The body of water under dis- 

 cussion has a shoreline (not including the chain of islands separat- 

 ing the lagoon from the ocean) of about 100 miles which is eroding 

 very rapidly in summer. During the fall of 1949 not only was the 

 ocean muddy but also great quantities of tundra (lichen masses and 

 grasses, including roots) were floating in it. This large amount of 

 organic matter, derived mainly from the eroding shoreline of the 

 lagoon and from the rivers, furnishes the detritus of the ocean floor 

 to a distance of 25 miles from shore, which was as far out as dredging 

 was carried on. It is my opinion that such material from the shores 

 of the Arctic Ocean and contributary rivers supplies detritus through- 

 out the entire Arctic Basin. 



Along the beach at Point Barrow and for hundreds of miles east 

 and west, erosion is proceeding at a rapid rate. Point Barrow proper 

 has receded 28 feet in four years — a rate of 7 feet a year. At one 

 place in Elson Lagoon the shore has eroded inland 115 feet in four 

 years. These figures were supplied by Dr. G. R. MacCarthy, of the 

 U. S. Geological Survey, who obtained them by measuring the tri- 



