Tendril of ice in the Weddell Sea
Nature can generate some perplexing patterns. Satellite images in April 2016, for example, showed mysterious lines criss-crossing the Caspian Sea. (It turns out those lines were caused by icebergs dragging their keels along the sea-floor.) Now images from the coast of the Antarctic Peninsula show another curious phenomenon: what looks like a tendril of sea ice snaking away from the ice pack in the Weddell Sea.
On 04 April, 2018, the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this natural-colour image of sea ice between various levels of cloud cover. As austral autumn progresses, sea ice around Antarctica is starting to grow again after reaching its annual minimum extent on 20–21 February.
The long, isolated patch of ice is a curiosity that is not easily explained. "The sea ice edge is usually pretty far south this time of year," said Ron Kwok, an ice scientist at NASA's Jet Propulsion Laboratory. "I have never seen a coherent feature by itself like that in the middle of the ocean that survives without melting."
Similar patterns show up in the atmosphere on the lee side of icebergs. These so-called "von Kármán vortex" streets arise when winds are diverted around a blunt, high-profile area—often an island rising from the ocean, or sometimes an iceberg. The alternating direction of rotation in the air forms swirls in the clouds.
View the full resolution image.
Credit: NASA Earth Observatory, Joshua Stevens, using VIIRS data from LANCE/EOSDIS Rapid Response.