A larger volume of younger ice meant that a larger portion of it made it through the summer and was available to form second-year ice
The salt content in first- and second-year ice
gives them different electrical properties than multi-year ice: In winter, when the surface of the sea ice is cold and dry, the microwave emissivity of multiyear ice is distinctly different from that of first- and second-year ice
But, most of the 2009 September Arctic sea ice is thin first- or second-year ice
, rather than thicker, multi-year ice that used to dominate the region," said Meier.