The US Naval Institute News has published a chart, prepared by the USCG, listing their best estimate of the world icebreaker fleets. Ships are listed by country, horsepower class, and year the ship entered service. Ships under construction or planned are also listed.
Only ships of more than 10,000 Brake Horse Power (7,457 MW), capable of independent Arctic operation, are included. There are notations to indicate nuclear propulsion, whether the ship has made it to the North Pole, whether it is government owned, and if the ship is designed specifically for the Baltic.
Chuck Hill's CG Blog 
Could you provide a link to this chart? Thanks Chuck
Sorry, thought I had. Correcting.
Anyway here it is: http://news.usni.org/2013/07/23/u-s-coast-guards-2013-reivew-of-major-ice-breakers-of-the-world
Note Mackinaw is not on the chart because it has only 9,119 SHP (6.8 MW).
I found I had to enlarge the chart to see it clearly.
There are some errors in the chart, not to mention numerous misspellings.
There are no definite plans to produce the 110-megawatt behemoth (“L-110”) and even if there were, it wouldn’t be ready by 2017 as the ship has not been ordered yet. Also, Toboy is missing.
The new Finnish icebreaker (in service by winter 2015-2016) is also missing.
Also, I don’t agree with including icebreaking cargo ships such as Vasiliy Golovnin into the list of icebreakers. There are other cargo ships with identical or considerably better icebreaking capability as well, but they are not “icebreakers”.
The chart has been updated again:
Click to access 20170501%20major%20icebreaker%20chart.pdf
Tups, thanks, I have added a link to this on my reference page as “Icebreakers of the World”