Ice Blades in a Small Frozen Pool

May 25, 2018

IceNeedles_DSCN4845 - Copy

May 2018 Viewer's ChoicePhotographer: Kathy Arbuckle 
Summary Authors: Kathy Arbuckle; Jim Foster

The photo above showing curious blades of ice was taken on a chilly late March morning in eastern Washington State. The temperature registered 27 F (-3 C). It was cold enough to freeze the shallow pool of rainwater that had accumulated in one of the ends of a large (about 24 in or 60 cm diameter) plastic spool. Each blade grew jutting upward at the same angle as it emerged from the icy pool. The largest formation pictured here measures approximately 4.5 inches in height (11.5 cm)

It's likely that clear skies allowed temperatures to drop quickly during the overnight hours, permitting fast freezing (supercooling) of the little pool. Since water typically freezes first along the edges of an enclosed container, the volume of water in the center of the pool, where the blades emerged, tends to be slightly raised and is last to freeze. Expanding ice beneath the surface of the water forces the remaining liquid water out through the hole near the center, forming a hollow protrusion. Bizarre shapes, including needles, spikes and sails can result. The small size of the pool, the confined space, differential freezing rates all play a role in determining whether or not protrusions will occur and the shape they'll take. In addition, because of the preferred growth of ice in crystalline planes, the protrusions often are at similar angles (often 60 degrees) to the ice-covered surface.

If you have a frost-free freezer perhaps on occasion you've noticed sharp spikes form on ice cubes. Photo taken on March 23, 2018, at 6:50 a.m.

Photo Details: Camera: NIKON COOLPIX P90; Software: Microsoft Windows Photo Viewer 6.1; Exposure Time: 0.012s (1/81); Aperture: ƒ/4.5; ISO equivalent: 160; Focal Length (35mm): 129.