Anchor-ice formation and ice rafting in southwestern Lake Michigan, USA

Anchor ice, i,e,l ice attached to the bed in a lake, stream, or ocean, is c ommon in the nearshore zone of southwestern Lake Michigan during winter. La custrine anchor ice has at least four distinct morphologies and was observe d on sand, pebble, and boulder substrates in water depths to 4 m, the limit of diving traverses. The maximum depth of anchor ice formation may he much greater. Anchor ice is released from the lake bed on mornings following fo rmation events. Released, floating anchor ice carries sediment to the water surface. This sediment is ice-rafted along shore and offshore under the in fluence of prevailing winds. We estimate that similar to 0.85 m(3) of sand per meter of beach is being removed from the nearshore zone of southwestern Lake Michigan hy anchor ice annually, Melting ice drops this sand in deep water far from shore. This is a significant loss of sand from the sediment- starved nearshore zone of southwestern Lake Michigan.