Ice crystal structure of multi-year ice sampled at the North Pole

Temperature and salinity profiles for the same core from the North Pole

Tony Gow, Erk Reimnitz, Bill Bosworth and Terry Tucker taking cores of dirty ice

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Sea Ice

of incident solar ra-

Ice crystal structure

pearing to have solid bottoms, obvi-

of multi-year ice

ously had an established hydraulic link

sampled at the

North Pole.

with the ocean below. Cores through

the bottom ice verified this, showing

rotten ice with interconnecting chan-

nels. Colors of the ponds varied from

very light blue to deep dark green. The

color depended on the pond depth, the

condition of the bottom ice and bio-

logical activity. Chlorophyll a concen-

trations were found to be substantially

larger in green freshwater ponds than

in the light-blue ponds. The albedos

of the ponds also depended on depth

and color. Deep ponds with rotten bot-

tom ice had albedos of 0.09; albedos were

as high as 0.3 for shallow light-blue ponds. Frozen snow-

covered ponds farther north exhibited albedos of 0.8.

A two-stream radiative transfer model (Perovich 1990)

has been used to estimate the partitioning of incident solar

radiation into that reflected back to the atmosphere, that

absorbed by the ice, and that penetrating the ice to the

ocean or directly into leads. The results show a dramatic

decrease in the solar radiation absorbed into the ice after

18 August, when fresh, light snow covered the ice. The

model points out that most of the radiation absorbed by

the ocean comes from the absorption by leads, rather than

through the ice.

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