The ‘surface scattering layer’ (SSL) is the highly-scattering,
coarse-grained ice layer that forms on the surface of melting, drained
sea ice during spring and summer. Ice of sufficient thickness with an
SSL has an observed persistent broadband albedo of
~0.65, resulting in a strong influence on the regional
solar partitioning. Experiments during the MOSAiC expedition showed that
the SSL re-forms in approximately one day following manual removal.
Coincident spectral albedo measurements provide insight into the SSL
evolution, where albedo increased on sunny days with higher solar
insolation. Comparison with experiments in radiative transfer and global
climate models show that the sea ice albedo is greatly impacted by the
SSL thickness. The presence of SSL is a significant component of the
ice-albedo feedback, with an albedo impact of the same order as melt
ponds. Changes in SSL and implications for Arctic sea ice within a
warming climate are uncertain.