Air photo interpretation of Great Lakes ice features / Ernest W. Marshall.

BALL ICE FORMATION

Ball ice consists of roughly spherical masses of slush and frazil ice which accrete in turbulent water.
Loewe (1949) reported ball ice 3-5 cm in diameter in the sub-Antarctic waters of the South
Atlantic and ascribed its origin to the accretion of slush and frazil ice.
Ball ice in the Great Lakes was observed by the writer in a nearshore zone of Lake Huron
in the Rogers City area, Michigan. The ball ice formation was observed during a time of intense, local snow squalls which left patches of slush on the water surface. This ball ice was
composed principally of slush which was shaped by the turbulent water conditions offshore from
the cliffed icefoot into lumps and balls up to 1 meter in diameter (see Fig. 19). The lumps that
formed in the less turbulent zones, a few tens of meters offshore, were flattened discs, while
those that entered the extremely turbulent zone near the ice foot accreted into spheres.
Water turbulence at the foot of the icefoot stirred sand into suspension causing lumps entering this zone to accrete concentric bands of sand and slush (see Fig. 20). As a result of
intense wave action these balls were thrown onto the icefoot where they froze and added sand
and ice to the barrier. In other cases the ball ice was carried by winds and currents into coves
where it collected to form a uniquely structured ice sheet (see Fig. 21). This drift of the ball
ice serves to redeposit sand both along the shore and in deep-water sites.
Ball ice has been observed in other areas of the Great Lakes. During ice reconnaissance
flights over Lake Superior in early January, the writer observed wide zones of this type of ice
along the shoreline west of the Keweenaw Peninsula and along the Marquette shoreline. In
these areas rough lumps up to 2 meters in diameter were frequently observed. Extensive
fields of loose ball ice were observed in the western basin of Lake Erie, while later in the
season similar fields were observed frozen in a matrix of clear ice (Fig. 22). Ball ice has
also been frequently observed along the Lake Ontario shoreline east of Oswego, N. Y. (A. G.
Ballert, Personal communication).
*Director of Research, Great Lakes Commission, Ann Arbor, Mich., 1965.

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