In the news over the last couple weeks has been some bizarre ice formations. In fact, it seems like around this time each year as temperatures dip, we are surprised anew at the way the world works when we hit a freezing point. Specifically, we've been fascinated by what are called frost flowers. There are a couple types -- those that form on land and those that form over water. Here is a closer look at each.
First, let's look at the frost flowers that form on the sea. These blossoms of ice sprout up when weather conditions are just so, and are similar to hoar frost.
NPR reports, "They aren't flowers, of course. They are more like ice sculptures that grow on the border between the sea and air. On Sept. 2, 2009, the day Jeff's colleague Matthias Wietz took these pictures, the air was extremely cold and extremely dry, colder than the ocean surface. When the air gets that different from the sea, the dryness pulls moisture off little bumps in the ice, bits of ice vaporize, the air gets humid — but only for a while. The cold makes water vapor heavy. The air wants to release that excess weight, so crystal by crystal, air turns back into ice, creating delicate, feathery tendrils that reach sometimes two, three inches high, like giant snowflakes. The sea, literally, blossoms."
Handy dandy Wikipedia tells us, "On lake ice, frost flowers are effectively identical to hoar frost crystals. On sea ice, brine is wicked up onto the hoar frost crystals, which leads to high salinities of up to 100psu (ppt) (approximately three times more salty than sea water)."
A second kind of frost flower, which is an entirely different phenomenon, occurs on land and actually does involve plants.
In late autumn or early winter, when air temperatures drop to freezing but the ground has not frozen, the sap from long-stemmed plants expands and creates cracks along the stem. Water is drawn through the cracks and freezes as soon as it hits the air. The more water drawn up through the stem and out of the cracks, the more layers are created, pushing farther out from the stem like frozen ribbons, or "flowers".
Incredibly delicate and easily melted, the frost flowers are visible usually in the mornings before the sun warms the air temperature.
It's truly mind-blowing the way changes in weather and shifts in temperature can create these small, temporary, beautiful sculptures out of air and water.