Abstract:

In this paper,the difference of Chukchi Sea ice distribution in 1999 and 2003 is studied by using the satellite remote sensing data form NSIDC.The results showed that the total sea ice in 2003 was obviously lighter than that in 1999.Sea ice cover was decreased in the spring and autumn of 2003. The sea water coming from Bering Sea passed the Bering Strait and entered into the Chukchi Sea half month earlier than that in 1999,which caused the sea ice melt seriously. However, the increase process of sea ice area was slowed down in July and August of 2003, and the ice area was close to that of 1999. In the autumn, the sea ice freezing process was postponed greatly, at least half month. The difference can better explain the heavy ice we met in 1999 expedition and the moderate ice status in 2003 expedition. The most important reason for lighter ice in 2003 is the higher air temperature (SAT).The SAT in 2003 spring and autumn were much higher than that in 1999, and the highest SAT difference record is about 18°C in coastal area of Alaska. The notable warmer weather provides the extra heat to decrease sea ice in 2003.Another factor acting on Chukchi Sea ice is the difference in wind field between the two years.The water flux from Pacific is greatly affected by the local wind field in both Chukchi Sea and Bering Sea.In 1999, the wind went against the entering of Pacific water in spring,whereas wind in 2003 spring is benefit to the entering.The southern wind occurred in both first few days of November 2003,caused the delay in sea ice freezing in autumn.The disagreement of the meteorologic factors in both years could be attributed to the difference in AO index,a larger scale process. AO index is positive in 2003 and negative in 1999, which determined in great extent the different pattern in both years.