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Diving investigations confirm previous circumstantial evidence of seafloor freezing and anchor ice accretion during freeze‐up storms in the Alaskan Beaufort Sea. These related bottom types were found to be continuous from shore to 2‐m depth and spotty to 4.5‐m depth. Spotty anchor ice occurred as pillow‐shaped crystal aggregates on buried slabs of frozen sand surrounded by unfrozen sand. Considerations of required conditions for ice bonding and anchor ice growth allows regional extrapolation and suggests the possibility of anchor ice growth out to 20‐m depth, the estimated maximum depth of supercooling during fall storms. Anchor ice and seabed freezing apparently do not develop during a calm freeze‐up. Because of the abrupt growth of anchor ice during a freezing storm and its release soon after formation of a surface ice cover, this ice type has not been documented before. The concretelike nature of frozen bottom, where present, should prohibit sediment transport by any conceivable wave or current regime during the freezing storm. But elsewhere, particularly where the bonded crust is broken by grounded ice, anchor ice lifts coarse material off the bottom and incorporates it into the ice canopy, thereby leading to significant ice rafting of shallow shelf sediment and likely sediment loss to the deep sea.

One feature of high-latitude areas is the formation of ice clusters attached to the beds of rivers, lakes and the sea. This anchor ice, as it is widely known, plays an important role in mobilizing bed sediments, as well as ecological roles as a food source, habitat and potentially fatal environment. Much work has been devoted to fluvial anchor ice in the Northern Hemisphere, yet comparatively little work has described anchor ice in polar marine environments, despite its description by Antarctic expedition scientists over a century ago. In this paper, we review the current understanding of anchor ice formation in polar marine environments. Supercooled water is a necessity for anchor ice to form and frazil adhesion is the most likely common mechanism for initial anchor ice growth. Strong biological zonation has led some authors to suggest that anchor ice does not form to depths of greater than 33 m, yet in Antarctica there appear to be no physical reasons for such a limit given the production of supercooled water to substantial depths associated with ice shelves. Future work should focus on the potential extent of anchor ice production and identify the key oceanographic, glaciological and meteorological conditions conducive to its formation.

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