Emperor Geese are more often associated with arctic and sub-arctic Alaska (and Russia). It sounds like there are four prior records in Sonoma County (in 1978, 1994-1995, 1996-1997, and 2001).
Here are a few photos from different perspectives.
Sitting:
Watching the waves:
With Black Oystercatchers:
Searching for food and eating some green algae:
Profile view:
Many thanks to Scott for spotting this goose and to Dea for passing along the sighting.
P.S. I was curious about the species name. Apparently "canagicus" refers to the island of Kanaga or Kyktak (in the Aleutian Islands).