Thank you so much. I wasn't 100% sure - they vary so much in looks and color. I have also posted a photo of his friend which I am also pretty sure is one as well. Would you be able to confirm that for me as well

I'm not an expert, but to me, this looks close to the widespread North American species Argiope trifasciata. Compare, for instance, such images of that species as:

Spiders of North America does not list Argiope bruennichi, but does list trifasciata from several provinces of Canada. This map from the British Arachnological Society does not show that species from Alaksa. (It could be incomplete of course, like many range maps.) I can't find any information on Alaska per se on the Internet. Certainly a number of Old World species from many taxa do occur in North America only in Alaska.
Looking at images of Argiope bruennichi on the Internet, it does seem to resemble Argiope trifasciata rather closely, but perhaps the photo at top does match bruennichi better. Compare, for instance, the image above (on left), with an image of bruennichi from Germany (right):

Can anyone shed light on this issue? This seems to be a notable record for the guide, if correct. It would be helpful to have some more information on how to differentiate the two species and to have some references from collections or checklists from Alaska.

that Jeff had commented on one of these Alaskan images, but now there seems to be only one image. We had questioned the earlier image identification because the species was Old World, but seem to remember that Jeff was comfortable with the ID. I wonder if that means we lost the image which contained his comments. You might drop him an email and see what he recollects.