Iceballs Answer
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Hi, I'm Bryan Yeaton and this is the Weather Notebook.

In yesterday's segment, listener Ann Alpern of Buffalo, New York asked us if we could help her identify the large round objects she found on the shore of Lake Erie after an autumn storm.

We called regular Weather Notebook contributor and meteorologist Keith Heidorn to find out what Ms. Alpern found.

"What the questioner saw are called appropriately enough, ice balls and are likely common on the Great Lakes during the winter. Their formation early in the cold season arises because Lake Erie is the shallowest of the Great Lakes. It normally freezes beginning in late November or early December. When the water temperature drops to near freezing, slabs of ice usually form first along a shoreline exposed to strong wind and waves. But rather than form as large uniform sheets, lake ice begins as irregular, flat chunks of ice scattered along the water's edge. Much of this ice is broken up over time by wind and wave action along the shore, and smaller chunks can float back out into the lake. If wind and wave are high, these chunks are quickly pushed back onshore forming an "ice foot" from the beach into the water. But, if the waves are small and wind light, some chunks move out into the lake. These floating chunks then become rounded into balls through their jostling in the waves. The iceballs then can migrate along the longshore until they melt or are again tossed back onshore. After time, grounded ice balls lose their rounded character and combine with other ice pieces to form the shore ice seen each winter. The observed ice balls likely picked up bits of weed and shells when they first froze on the shoreline.

That's meteorologist Keith Heidorn who lives in Victoria, British Columbia. The Weather Notebook is a production of the Mount Washington Observatory. Our show is underwritten by Subaru and the National Science Foundation.