Bruce, these are beautiful shots, you are a lucky guy to do that trip! I'm extremely jealous. I'm sure the only time I'll ever get to see the arctic is if I have to do construction there...doh.
Can you tell me what f-stop you used? I've been thinking about getting the 500, but these shots have some WEIRD looking bokeh.
Cheers
James
Thanks for the compliments, James. Many of those shots were 90% luck and only 10% skill, but that doesn't mean I'm throwing 'em away! 
I'm afraid that's too far North for drilling (although I'm sure George W. would give it a try if it belonged to the U.S.! 
), but I hope you do get up there some time...before ALL the ice is gone (it is retreating--and therefore removing the polar bears' hunting habitat--rapidly...very sad, but that's another topic).
I shot shutter priority on almost all of the animal excursions, primarily because we were in a bobbing zodiac with only hand-held cameras, so I knew my only hope of in-focus pictures with a long lens was a high shutter speed. In order to get those speeds, I generally used ISO of 200-400, and I just tried to keep the shutter speed at 1/800 - 1/1250 (depending on how bouncy the zodiac was) if lighting would allow (MANY of the shots were 1-2 stops underexposed; thank heavens for RAW!). The entire equation would have changed dramatically if we had been on solid ground (or ice) with a tripod!
If you go to The Svalbard Gallery on my Website and look at the EXIF info on these photos, you'll see that many of the shots ended up being at pretty wide open f-stops (considering the fact that I was using a 2X TC on many of them). And the EXIF info seems a bit squirrely with the 2X TC, e.g., on shots taken with the 100-400mm and 2X TC it only shows the lens length as 400 (rather than 800mm). With the 500mm lens and 2X TC, it always seemed to register the focal length as 1000mm. (Note: the 2X TC was a Canon, but it was an OLD one that I borrowed from a professional photog on the boat - I somehow left mine home! So that might have been part of the problem with EXIF data being weird.)
All that aside, my impression of the 500mm f/4 lens is that it is AWESOME! While I was reasonably happy with how it performed with the 2X TC (accurate AF, decent sharpness, etc.), I was blown away with how it performed by itself! The image in the viewfinder just jumped out at me with clarity and sharpness, the AF was great, and I have no doubt that the IS made hand-holding possible! One person had a brand new 600mm, and I suppose it is even better, but I think the 500mm is a more practical (if we can use that word for these monster lenses!) choice. If I had taken my 1.4X TC (which I also somehow forgot!), I likely would have used that part of the time with it, but I actually think I might have gotten better results with just the 500 alone (and heavy cropping after the fact).
As for the weird bokeh on some of these photos, you really need to bear in mind that they are not only taken with a 2X TC, but that the background/negative space in many of these photos is WAY the hell back there (e.g., mountains 10 miles away) with a huge expanse of ice (which bends light weird ways anyway) in between. In some respects, it's like taking a photo in the desert or along a LONG highway in the sun -- the light gets dramatically distorted by the distance and "wavery" air in between (I'm sure there are scientists who can explain it WAY better than that, but you get the idea). The air was cold, crisp, amazingly clean (NO pollution), and I noticed how weird the faraway backgrounds looked -- not just through the lens, but in person. In short, I think for bokeh analysis, you need to look at a lot of other photos taken with the lens, rather than these...
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