Major Findings 3 



small ridges pushed up by the growth of underlying ice wedges. The total 

 area enclosed by the ridges is about double the pond area. Despite the 

 minuscule drainage basins and the desert-like levels of precipitation (12 cm 

 annual, 50% falls as rain in June through September), the surrounding 

 tundra is often saturated and the ponds do not dry up. Water flows from 

 one basin to another for only a few days during the spring runoff. There is 

 no belowground water movement from basin to basin or into the sediments 

 because of the underlying permafrost. 



From late September until mid-June, the ponds and their underlying 

 sediments are solidly frozen. Melting of the ice in the ponds occurs over a 

 few days in the spring and water temperatures can reach as high as 16°C 

 any time thereafter. Thawing of the sediments continues throughout the 

 summer until 30 cm are thawed. The ponds are so shallow that the water 

 temperature can change as much as 10°C per day in response to sunlight, 

 air temperature, and wind. June, July, and August are cool (mean air 

 temperature is 2.8°C), cloudy (83% cloud cover), and windy (an average of 

 6.1 m sec ~ ^) so the mean water temperature is low, around 6°C. 



FIGURE 1-2. The intensively studied ponds near Barrow, Alaska. A 

 small field lab is at the upper left of the picture and experimental sub- 

 ponds in Pond B are at right. An aerial cable car is suspended above the 

 subponds. 



