From the air, it looked like a weather system: a vast white swirl with a well-defined centre sitting just off the coast of Labrador.

But on closer inspection, what appeared to be a strong storm was actually a mass of sea ice caught in an ocean eddy, or circular current of water.

Kyle Roberts, a meteorologist with KOKH-FOX 25 in Oklahoma City, tweeted images of the ice gyre captured by a pilot friend, along with a NASA satellite image from June 26 confirming the size and location of the eddy.

Not a hurricane…sea ice caught in an eddy off of Newfoundland and Labrador, Canada. Via a pilot friend of mine. pic.twitter.com/bpAxLqMPSN — Kyle Roberts (@KyleWeather) July 3, 2016

Ocean eddies are common but rarely visible to the naked eye. In this case, explains The Weather Channel, the eddy was likely caused by the clash between the frigid Labrador Current and the warm Gulf Stream, which due to their temperature have different densities. Chunks of ice drifting south from the Arctic just happened to get caught in the middle, putting on a spectacular show for aircraft and satellites for more than a week before the eddy dissipated.