Picture this, if you will: A foolhardy photographer has made his way onto a large frozen wetland slough in a prairie along the Platte River. After his boots punctured the thinner ice along the edge of the slough, he has carefully, with dripping boots,stepped up onto the marginally thicker ice beyond and is now army crawling across the frozen surface, trying to ignore the cracking sounds all around him each time he moves. He knows his life isn’t in danger (the water is only a few feet deep and he’s 50 yards from his truck), but there seems a very good likelihood of submerging the camera equipment he’s carrying and of getting suddenly and uncomfortably wet and cold.
From a distance, it’s hard to see what the photographer is risking so much to photograph. Every minute or so, he appears to stop and aim his camera at the base of rushes and other plants protruding from the ice, even changing lenses several times to get different perspectives. Of plant stems in the ice? What a loon. …Actually, that’s a patently unfair slam on loons, which have infinitely more sense than this chucklehead seems to have.
Let’s hear the explanation in the photographer’s own words, for whatever that’s worth.
Yeah, I get it. And I’m glad (as I very often am) that no one was ACTUALLY watching as I slid myself and my gear across the ice earlier this week. But what I was chasing were little cone-shaped pieces of ice suspended above the frozen surface of the wetland. I found them strangely attractive and an intriguing mystery. What caused the ice to form a cone in the first place, and why were those cones so far above the surface of the surrounding ice?
I certainly don’t have a definitive answer to those questions, but I have hypotheses. I’m guessing there are pieces of relevant information, including that it both rained and snowed recently, that temperatures have been hovering right around the freezing mark over that same time period, and that there is water flowing out of the slough and – probably – lowering the level of the ice.
Even with all that information, though, I’m still struggling to understand exactly what I was seeing. I’m thinking maybe the raised cone-shaped ice was formed by snow/sleet/frozen rain accumulating at the base of the plants – both because of wind eddies around the stems and maybe also water running down the stems from above. I’m pretty sure the elevation of the ice went down in the days prior to my little photo adventure. But how did the cones become detached from that ice?
Whatever happened, it created an awful lot of those little cones across the top of that particular wetland slough and others like it. I’m guessing a more experienced and smarter person than I could have drawn helpful inferences from the uneven surface of the ice. There were shallow cavities in some places and raised areas in others, but for the life of me, I couldn’t figure out what was driving that pattern. Instead, I focused on photographing the cool little cones and trying not to get anything other than my waterproof boots wet. In that, at least, I was successful.
The Prairie Ecologist 
You need to become an ice archaeologist. I have not seen your ice skirts, but have seen somewhat related phenomena, including a fish in a tree. My take (guess) on what you have is the following: The water level was higher when it started to freeze on the upright stems. It gradually lowered before the surface of the water froze, but the air temperature was low enough to freeze your funnel shapes as the level of the water became less. Growth of the skirt would cease when the surface of the water froze. It is also possible that water splashing was involved if it was quit windy before the main body of water froze over.
Roadside and farm field water puddles sometimes produce interesting designs on the underside of the ice sheet if the water underneath soaks away during the freezing process.
I came across this phenomenom (or something similar) last winter at Lake Manawa across the river in Iowa. The weather lake was not frozen at the time but it had been previously – so the water was quite cold. The temperature plunged down to the single digits and there was a night of strong northwesterly winds which drove the water up on the dead lotus stems that grow along the southern shore. The next day the winds had died down and the sky was clear. And as I drove the stretch along the southern shore (this is around Boy Scout Island) early in the afternoon, the ice clinging to the stems almost blinded me as they reflected the sunlight into my eyes. It was impossible to focus on them and see their form but later on it was apparent what had happened. It happened again several weeks later but not so well. I’m waiting for the next time when the conditions are right to see if I can get some photos.
My guess (pure speculation!) is that there was a layer of snow atop the ice, then nearly frozen rain drops traveled slowly down the stems and froze when they reached the snow. In more open areas, the raindrops (with the additional force from gravity) melted/compacted the snow, refreezing at the water level. Since then, the remaining snow around the stems melted, leaving the ice suspended.
The only bit I can add is the cones are much like stalagmites in caves. As the sun warms the stems, frost melts and the water runs down the stems until it reaches the snow or ice and forms a cone. I think Danelle has solved the mystery of the suspended cones. As Danelle mentioned, the drops “froze when they reached the snow.” The sun warmed the surface of the dark ice (under the snow) enough to melt the snow leaving the cones of ice suspended. The topography of the ice is probably due to splashing as the ice was freezing which Paul contributed. Although, it appears in some cases the cones may have acted like magnifying glasses concentrating the sun and causing ice to sublime faster under the cones.
This is just too funny. Shortly after I read this yesterday (it was still up on my computer), my colleague called me over to his computer to show me a photo he took two days ago of the exact same thing, which he found on a stem at a little spring behind the nature playscape here at work. I showed him your piece (since it was still up). We pondered it. We thought about ice level dropping, but didn’t know that there had actually been a high level of ice at the spot where he found it – it was mostly just plants, the spring being more of a seep than standing water. For us, as you, it remains a ponderable.
Uneducated guess(?): https://beetlesinthebush.wordpress.com/2010/01/22/friday-flower-crystallofolia-frost-flowers/
I like the wet stem theory. Near freezing water ran down the stem and froze in the micro climate just above the ice level. As water ran down it ran over the frozen ring on the top side and froze around the rim of previously frozen ice, giving it the cone shape. The air/water temps and the rate of precipitation against the reeds would have to be just right. If it acquired moisture accumulated too slow it would freeze along the length of the stem and be a “stem-cicle”. If the rate was too fast it would not freeze before draining into the lake. I wonder how the distance above the ice each ring varied. Lets say they were all one inch, that would be a clue. If they varied one to 3 inches that would tell a different story.