From Bright Windows to Dark Spots: Snow Cover Controls Melt Pond Optical
Properties during Refreezing
Abstract
Melt ponds have a strong impact on the Arctic surface energy balance and
the ice-associated ecosystem because they transmit more solar radiation
compared to bare ice. In the existing literature, melt ponds are
considered as bright windows to the ocean, even during freeze-up in
autumn. In the central Arctic during the summer-autumn transition in
2018, we encountered a situation where more snow accumulated on refrozen
melt ponds compared to the adjacent bare ice, leading to a reduction in
light transmittance of the ponds even below that of bare ice. Supporting
results from a radiative transfer model suggest that melt ponds with a
snow cover >0.04 m lead to lower light transmittance than
adjacent bare ice. This scenario has not been described in the
literature before, but has potentially strong implications for example
on autumn ecosystem activity, oceanic heat budget and thermodynamic ice
growth.