Sea ice ablation is an important physical process affecting the global climate system. During the Arctic melt season, rapid changes occur in both sea ice surface conditions and the extent of ice. These changes alter the albedo and vary the surface energy budget. Understanding variations in Arctic sea ice is critical for global climate studies. This paper investigates the spring onset of melt in the Arctic seasonal sea ice zone through analysis of melt signatures derived from Nimbus 7 scanning multichannel microwave radiometer data. Satellite-derived melt signatures, determined by 18- and 37-GHz vertical brightness temperatures, are associated with the initaal melt of the snow pack on the sea ice surface. Sea ice melt events vary spatially and temporally. Within the arctic basin the melt signature is observed first in the Chukchi Sea and the Kara and Barents seas. As melting progresses, the melt signature moves westward from the Chukchi Sea and eastward from the Kara and Barents seas to the Laptev Sea region. The initial location of the melt signal also varies with year. In 1979 the melt signature occurs first in the Chukchi Sea; and in 1980 in the Kara Sea. The data for the initial melt varies between 1979 and 1980 by an average of 7--10 days with a maximum of 25 days in the Chukchi Sea region. Monitoring the occurrence of melt signatures can be used as an indicator of climate variability in the Arctic's seasonal sea ice zones. ¿ American Geophysical Union 1987