649 



Figure 12. Maximum and Minimum Extent of Ice 

 Edges 



Figure 13. Average Annu.alIceDriftin the Arctic 

 Basin 



The extent oj the Arctic tee cover undergoes a large seasonal flucltwiton. 

 between an average of about 16 million square kilometers in winter 

 {March} to 8 million square kilometers in summer l.\ugust}. Ytar to year 

 variations are large in specific sectors, but averaged over all longitudes, 

 they are only a few percent. 



The northernmost position of the Arctic sea ice edge at each longitude is 

 shown in white for summer and grey for winter 



The Navy 's Historical ke Morphology data are a refinement of the long 

 term averaged view shown here, and include information about ice condi- 

 tions and composition on finer spatial and temporal scales. 



b. Accessibility 



Mos; of the Navy's best historical ice morphology data for the 

 Arctic are classified today. A closer review is needed to 

 determine how this data set could be made more accessible. 

 Although NIC does not provide direct project support to non- 

 governmental organizations, the primary NIC unclassified 

 derived product (the bi-weekly global sea ice assessment) is 

 available to the general public via computer file transfers. NIC 

 also indirectly supports a variety of private activities such as the 

 sea lift resupply of communities along the North Slope of 

 Alaska and winter fishing fleet operations in the Bering Sea. 



Ice drift direction and speed data are represented by vectors. 



Arrows represent the direction ofict dnfi across the Arctic Basin: the 

 speed is proportional to the length of the arrow. The ice moverient 

 "fronts" are shown in yearly intervals. 



Solid lines labeled J -6 indicate the tikelv number of years thai ic e will 

 sur\'ive before it exits the Arctic Ocean through the From Strait {between 

 Greenland and Spitsbergen) or melts in ;he warm water near ihe coast 

 during summer. 



c. Scientific Utility 



The sea ice cover of the polar regions exhibits complex 

 interactions and feedback that affect both local Arctic climate 

 as well as the climate of more distant, inhabited temperate 

 regions of the globe. Bctli tfie extent and the thickness of sea 

 ice are believed to be particular!;, sensitive to subtle changes in 

 climate, a sensitivity that is believed to be particular!) important 

 over the outer continental shelves of the Arctic. Also, model 

 calculations for a wide range of greenhouse warming scenarios 

 predict the poleward amplification of climate change, which 

 should be accompanied by a reduction in the sea ice cover. 



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