What are the approximate dimension of this iceberg? Any chance the ratio is 1:4:9?
Not likely.

Quoting Kelly Brunt, an ice scientist with NASA and at the University of Maryland, from What the Heck Is the Deal with This Weird, Square Iceberg? at LiveScience.com:


  What makes this one a bit unusual is that it looks almost like a square,


which does not rhyme with anything in your suggested 1:4:9 ratio.

The article mentions the obvious


  And, as with all icebergs, the part visible above the surface is just the top 10 percent of its mass. 


but that only tells you that 90% is under water, nothing about its absolute height above sea level.