soM£ v£r/A//r/0A/s or the ^Hcr^e 



, where the growing season 



s less than 

 50 DAYS 



Figure 2-1. — Some definitions of the arctic region. 



Many definitions use climate as a criterion to delimit the polar 

 areas. Based on temperature, the Arctic is defined as: 



1. The area lying north of the boundary fixed by the isotherm 

 of 50° F. (10° C.) for the warmest month, or the isotherm of 

 14° F. (minus 10° C.) for the coldest month. 



2. Areas having a mean annual temperature of 32° F. or below. 



3. All areas where the sum of the average temperature in de- 

 grees centigrade of the warmest month plus one-tenth of the 



18 



