Saturday, November 26, 2011

The Myth of Frozen Waves

In an outing in the Laramie Basin the other day I came across “frozen waves” on the downwind side of Sodergreen Lake. Had it really been so cold that the waves had frozen in place?
"It was so cold the waves just froze right there by the shore, yah, you bet! and I tell ya it took three days to thaw the fish out after we got home, that's how cold it was ..."

I thought maybe these wave-like ridges formed as water splashed on ice when the lake started to freeze at the margins.  Or perhaps the wind and waves moved chunks of ice towards shore before the lake was completely frozen.  Some research online identified this phenomenon as a nearshore ice complex, or NIC (from page 8 of this booklet):
"Ice ridges form where waves break, such as over nearshore sandbars ... There may be several parallel rows of ice ridges; usually there are more ice ridges than sand bars. Lakeward of the ice ridges, a zone of slush ice may collect. This slush ice can be driven repeatedly by waves onto the outer ice ridge, raising its crest 15 feet (5 meters) high or higher above the lake."
Nearshore ice complex on Sodergreen Lake, Wyoming, USA.
Sodergreen Lake in the southwest Laramie Basin.
Sodergreen Lake is only about 50 acres (20 ha) when full, so the NIC there isn't exactly spectacular.  Bigger lakes produce bigger ones.  NICs often protect against erosion but can do damage when chunks of ice are pushed against whatever is on shore.  Below left:  NIC on Great Lakes (USA); below right:  ice shove on St. Lawrence River (Canada).
When I was searching for information on nearshore ice I came across some REALLY spectacular "frozen waves" supposedly from the Great Lakes.  For myth-busting details, see Waves Frozen in Place?

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