When you think about the seas around the North or South Pole, what image comes to your mind? Most likely, you conjure up a picture of polar bears, icebergs, and frigid waters. Not every ice chunk floating in polar waters is an iceberg. Some are growlers.
To find polar ice chunks you have to journey to Antarctica, Greenland, or between latitude 55 degrees North and 60 degrees North off the coast of Alaska and Canada. Chunks of glaciers or shelf ice break away from the icy mass in a practice called “calving”. Summer finds massive icebergs decomposing into smaller versions of themselves. Each of these is identified according to its size. Icebergs are the largest and the easiest for ship radar to detect. Bergy bits are the next size down from icebergs and can jut up to sixteen feet above the water’s surface. They are not as easily detected on radar or by a watchful eye.
Growlers are rounded and smaller than bergy bits. They can be transparent at times and at other times have a black or green hue. While bergy bits float a bit higher in the water, growlers are unstable and float lower. As with the other polar ice chunks, about 90 percent of the ice mass floats beneath the water and 10 percent is visible. Growlers can be the most difficult to detect and are especially hazardous when they drift into shipping lanes. During rougher weather, they are nearly impossible to spot. The best time to identify a growler is when the sea is calm. Radar can then locate them at about 1.6 kilometers distance.
Growlers have been compared in size to a grand piano or a small sports car. Though most ships traversing polar waters have special hulls to endure going through floating ice fields, mariners still attempt to avoid growlers.
The earliest mention of growlers in polar expedition literature was in the November 23, 1912, entry by Robert Cushman Murphy in the Logbook for Grace when he mentions “Doubled lookouts for bergs and growlers were stationed at the bow.”
Growlers are named for the sound they make. David Lewis in the 1979 Voyage to Ice: the Antarctic Expedition of Solo described them as “a rounded bump of very dense ice from the core of the iceberg that wallows awash with a hollow roaring sound.” According to Rob Gell, author of Antarctica: Future of a Frozen Wilderness growlers “growl” when they “slide along a ship’s hull.”
Growlers seem a strange name to attach to a polar ice chunk, but some means of identification have to be used by those who navigate berg-laden waters.
Resources:
Hince, Bernadette. The Antarctic Dictionary: A Complete Guide To Antarctic English. CSIRO Publishing, 2000.
Essen, Marty. Cool Creatures, Hot Planet: Exploring the Seven Continents. Encante Press: Corvallis, MT, 2007.
http://weblog.greenpeace.org/oceandefenders/archive/2005/11/
http://www.britannica.com/titanic/iceberg.html
