3 August, 2003
Ice is misleading. At first glance, it all seems the same. Sure, some pieces are thicker and larger than others, but it's still plain ol' ice, right? If you take a closer look, you'll see that there is far more to it than just the "tip of the iceberg." Indeed, scientists have identified and described close to 20 different kinds of ice depending on whose classification system you happen to be looking at.
The first distinction has to do with the origin of the ice; that is, did it come from land or the sea? On land, it begins with water vapor which eventually condenses to form snow. If there's enough snow over a long period of time, you may end up with ice sheets and glaciers. These in turn can produce an ice shelf or ice bergs on the coast.
In the ocean, however, sea water freezes to form Frazil Ice, and later on, Grease Ice. That's interesting- greasy ice- I didn't know there is such a thing. Not only that, but come to find out, there is someone on board that is actually a grease ice expert. Dr. Karl Newyear knows all about the stuff. In fact, Karl earned his PhD studying how waves propagated through grease ice. If I remember correctly, waves speed up in grease ice that produces a recognizable pattern that can be identified from space using remote sensing techniques.
From grease ice forms an accumulation of spongy, white lumps several centimeters across called Shuga which Karl has observed along the way. Continued freezing will produce Ice Rind, then Pancake Ice, Fast Ice, and Pack Ice. Then there are Floes, five different kinds to be exact, from Ice Cake to Vast. Going back to land-originated ice, there are also Tabular Bergs, Bergy Bits, and Growler Ice.
Finally, a combination of ice fragments that can include wreckage of many of the forms mentioned above, you may get Brash Ice. This "wrecked ice" is what the Palmer has been busting through most of the time during our cruise according to Karl. Of course, the whole process repeats itself when the Brash Ice melts and becomes sea water again. From there it can directly freeze again, or evaporate and come down as precipitation on land somewhere.
One of the big questions up here is whether the ice that melts each summer exceeds the ice that forms every winter. Indeed, one of the goals of the Shelf-Basin Interactions program is to help us get a handle on that very question; however, it's going to take years and years of collecting data like we are on this survey cruise before we can even attempt to answer that about global warming.
In the meantime, I just plan to enjoy the grinding and groaning under the Palmer's hull as it shudders and rolls through the next patch of ice.
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