Summer Albedo Variability And Trend In The Chukchi Sector,1981to2012

We obtained albedo in Chukchi Sector from the Advanced Very High Resolution Radiometer (AVHRR)(level1B) after calibration, sun zenith angle correction, narrow-to-broadband reflectance conversion, anisotropy correction, and atmospheric correction. SMMR&SSM/I date sets, NCEP/NCAR Reanalysis1and OI.V2SST data sets have been used to calculate sea ice concentration, surface air temperature, sea surface temperature and summer sea ice minimum average and trends from1981to2012for the Chukchi Sector, to explaine the albedo variations.The results indicate a significant downward trend in the mean albedo in August from1981to2012. The albedo was between0.33and0.45prior to2006. Two historical lows appeared in2007and2012. The albedo increases with increasing latitude, with the values of approximately0.15at latitudes below70°N and between0.5and0.7at latitudes above75°N, where the sea surface is covered with ice. In the area between70°and75°N, the albedo varies between0.2and0.5and decreases significantly (at95%significance level) due to the melting of sea ice.As the albedo of Chukchi Sector in August reduced over the past32years, the sea ice concentration, surfacec air temperature, sea surface temperature and multiyear ice area also have rapid changes. Sea ice concentrations decreased significantly, and the spatial variation is very similar with albedo, the correlation coefficient is0.81. Surface air temperature in the hole area and sea surface temperatures in the open waters have increased about2℃overall. Meanwhile, multiyear ice coverage decreased, summer sea ice minimum area approximate7.0×105km2from the1980s, down to about1.0×105km2in2007, with an average annual rate of decline about20,000km2. These factors directly caused the decrease in albedo. Other factors, the accumulation of black carbon, the enlarging fractions of melt ponds and the timing of melt onset also play an important role in the albedo decline.The complicated weather and imaging conditions in the Arctic region have made research into long-term albedo variability difficult. The reasons for the albedo changes are complicated. This study confirms that the drastic changes in the albedo in the Arctic Chukchi Sector over the last decades, especially the significant downward trend, are closely related to the global climate change. However, the consequences induced by such changes and their interaction with the global climate change require further study.