Why it Snows in the Frozen North: Scientists Reveal How Arctic Snowflakes Form

Why does it snow so much in the frozen north? That's a good question, and now scientists may have an answer as to why drifts pile up in places like the Arctic.

Snow doesn't just materialize out of thin air. In order for snowflakes to form, they need a nucleus, a speck of dust, where water molecules can cling as their structure freezes. These ice-forming nuclei are relatively rare. Yet over the Arctic, where the atmosphere is very clean and the ocean is covered with ice, it can snow for days. So why is this exactly?

In order to find out, the researchers created a model to describe how ice crystals form, grow and fall. Then then backed up the model by using data on Arctic clouds, which are very well studied.

So what did they find? As the number of snow crystals increases, their mass soars by a power of 2.5. This was particularly surprising, since the scientists believed that it was more of a 1:1 ratio. Because the relationship is stronger, though, it explains why it snows so much in northern reaches. For example, if you triple the amount of crystals, the mass goes up by a factor of 16.

"The key assumption we made was that there's a hidden source of ice nuclei that's always there, but they are just really, really low efficiency," said Shaw, one of the researchers, in a news release. "The consensus in the research community has been that you need special pieces of dust to catalyze the ice. We thought, 'What if there was more stuff out there that would produce ice if you just wait long enough?' Maybe when you put it in contact with a drop of water, it doesn't freeze immediately. But if you wait an hour, or two hours, it does. Our model assumes that the atmosphere is full of those really inefficient nuclei."

The researchers aren't sure what the weak nuclei are, or even where they come from, but it seems like they exist based on the experimental data. It's very possible that they're what help cause the massive amounts of snowfall seen in places like the Arctic. Currently, the researchers are investigating a bit further in order to find evidence of these nuclei.

The findings are published in the journal Geophysical Research Letters.