The Challenge of Counting Icebreakers

The numerical gap is far less important than the gap between required and actual capabilities.

If you’ve been paying attention to U.S. Arctic Strategy or U.S. Coast Guard icebreaker acquisition, you’ve undoubtedly read that the U.S. only operates three icebreakers (two before the recently purchased Storis came online). And you probably know that the U.S. Coast Guard says it needs eight or nine icebreakers, four or five of which are medium icebreakers, in order to accomplish its mission.

On October 17th, the Arctic Economic Council published “an updated global inventory of icebreakers and major ice-breaking vessels.” Here is the chart that accompanied the announcement:

Wait, what? The U.S. has twelve icebreakers and three Arctic research vessels? I thought the U.S. only had three? If we need eight or nine and have fifteen, what’s the problem?

The AEC chart lists Aker Arctic as source. Last year, Aker published their own chart showing icebreaker numbers:

World icebreaking fleet 1 January 2024, according to Aker Arctic.

Note: Although the chart description and article title refer to “icebreakers,” context in the article makes it clear that this is both icebreakers and other major icebreaking vessels. More on this distinction later.

Counting Icebreakers by Vessel Purpose

Aker Arctic describes its methodology:

The diversity of icebreaking ships makes compiling an exhaustive list of icebreakers challenging. It is difficult to draw a clear line between ships that should be included and ships that should be left out.

In addition to purpose-built icebreakers, many research ships, offshore vessels, and even one luxury cruise ship have been officially classified as icebreakers. However, their ability to operate independently in difficult ice conditions is merely a means to carry out other tasks.

Although smaller ice-strengthened tugboats are often used for icebreaking operations in harbours, they are not considered as icebreakers. Oil tankers, LNG carriers, and other cargo ships are also excluded even if they are fully capable of independent year-round operation in the most challenging Arctic ice conditions.

Aker’s conclusions are subject to debate and quibbling. As they put it on X when considering creating an icebreaker poster (still not released):

Complicating efforts to compare icebreakers is the fact that each nation uses their own method of classifying icebreakers. Even when nations use the same nomenclature— as in the “heavy”, “medium”, and “light” categories used by both the U.S. and Canadian Coast Guards— their definitions are different. For example, the U.S. Coast Guard would classify the Canadian Coast Guard’s heavy icebreaker Louis S. St-Laurent as a medium icebreaker.

Aker’s process considers the purpose of the vessel and its specific design, not its icebreaking capability. This limits the utility of these charts in comparing icebreaking/polar capability between nations, as a small Great Lakes icebreaker counts the same as a PC 2 icebreaker capable of operating in touch polar ice conditions. This is why Aker list shows the USA having fifteen or sixteen icebreakers instead of the three polar icebreakers normally referred to in discussions of U.S. Arctic and Antarctic capability.

Included in Aker’s list are the very small (662 ton) Bay-class tugboats. The U.S. Coast Guard operates nine of these vessels for use in the Great Lakes and along East coast rivers:

Counting Icebreakers by Capability

U.S. Coast Guard icebreaker chart as found in the CIA World Factbook.

At first glance, this seems simple. You can just count vessels by the International Association of Classification Societies (IACS) Polar Class, as in the chart above.

As a reminder, here is the description from the IACS Unified Requirements concerning Polar Class:

IACS Polar Class Descriptions (IACS UR I1)

However, there are at least four problems classifying vessels by Polar Class.

First, as the American Bureau of Shipping notes in its Guidance Notes on Ice Class, these classifications are a measure of survivability in ice load conditions, not a measure of icebreaking ability:

Note that an ice class notation is verification that the hull and machinery are strengthened to withstand ice loads to a level corresponding to the vessel’s associated ice class. An ice class notation does not guarantee efficient performance in ice. The hull form, installed power, and crew capability/knowledge govern the ship’s performance in ice. Ice class rules do not prescribe requirements governing the hull form design.

Second, the Polar Class requirements only apply to vessels contracted on or after July 1, 2007¹. Before that, each classification society used its own criteria. Although there has been an effort to assign older vessels an ‘assumed’ Polar Class, the difference in earlier standards makes this at best imprecise. ABS describes the situation before the Polar Class rules were adopted:

Ice class rules have existed for many decades in Classification Society Rules and in Polar coastal nation rules. The different rule sets prescribed requirements which were dependent on the local ice conditions for a specific country’s waters or the Classification Societies’ school of thought. The large number of ice class rule sets led to confusion for ship owners/operators and significant work for regulators to determine if a vessel was compliant with a specific rule set. This led to many efforts to determine “equivalency” between ice class rule sets but often led to more confusion and disagreement between stakeholders.

Third, these rules only apply to vessels that intend to operate in polar waters, which includes Antarctic waters and international voyages in Arctic waters². The Great Lakes, St. Lawrence Riverway, and the Baltic Sea are key areas not included. Also excluded are vessels intended for use in Russia’s Arctic waters. This is why Russian icebreakers do not normally have a Polar Class, rather a class assigned by the Russian Maritime Register of Shipping (RMRS).

Fourth, while Polar Class (and assumed Polar Class) can be useful proxies for icebreaking capability, they are not the full picture.

For example, Finland’s Polaris, a PC 4 icebreaker, has a better icebreaking capability than many PC 3 vessels including the icebreakers Fennica, Nordica, Nuyina, Kronprins Haakon, Aiviq/Storis (assumed PC 3) and the icebreaking research vessel Xue Long 2. Nonetheless, Polaris is not designed for operation in polar waters. More on that later.

Polar Class is better than an earlier method of classification that uses the brake horsepower of the ship’s power plant³. Before the advent of podded propulsion units, this was a defensible system. But now, as modern podded propulsion units can achieve similar levels of icebreaking performance at far less power, this method makes little sense. Aker Arctic’s comparison of Polar Star (assumed PC 2, 60,000 bhp) and Le Commandant Charcot (PC 2, 46,000 hp), demonstrates this advancement:

What, then, is a polar icebreaker?

There is no easy answer to this question. One can say that a polar icebreaker (or a polar icebreaking vessel) is one that has a Polar Class, as it is strong enough to operate at the poles in a certain level of ice.

From a practical standpoint, though, not all Polar Class vessels are suited for all polar operations.

Earlier I mentioned Polaris, noting that this PC 4 icebreaker can break ice better than many PC 3 icebreakers. This superior icebreaking performance is largely because Polaris has a third Azipod mounted on her bow. This same feature is a liability in the polar regions, as pushing the bow Azipod through heavy multi-year ice risks damaging the pod and effectively excludes all but the most careful backing and ramming, an important technique when dealing with multi-year ice.

For older hulls (sometimes called “traditional” icebreakers), there is a tradeoff between icebreaking and open-ocean seakeeping. These icebreakers traditionally have found hull designs that generally handle poorly in open ocean conditions. For example, once the Polar Star starts rolling, she doesn’t stop, earning her the nickname “The Polar Roller.” For this reason some older hulls are not as suited for polar operations.

For modern designs, the tradeoff is far less, particularly when combined with a roll damping tank (as is installed in the Finnish icebreakers Fennica, Nordica, Otso, and Polaris.)

Other features can come into play such as crew size and a lack of endurance without refueling.

But in general, I’d say that a polar icebreaker is an icebreaker that can achieve its purpose/accomplish its missions in the polar region.

For the U.S. Coast Guard, this equates to two types of icebreakers. Heavy polar icebreakers must be able to accomplish the limiting polar mission, breaking ice for the resupply of McMurdo station in Antarctica. And they must be able to do this year after year following a long journey on the open ocean (conducting the U.S. Coast Guard’s other missions as it does so).

Medium icebreakers must be able to operate in areas and conditions where there is maritime traffic in the Arctic, particularly in the areas surrounding Alaska. And not just operate independently but be able to reach vessels in distress and provide assistance to them. A modern icebreaker with azimuth propulsion should be able to do this easier than the U.S. Coast Guard’s current medium icebreaker, Healy. These icebreakers must also be able to break ice to keep ports, such as Nome, Alaska, open when required. Indeed, Nome will likely be the future home port of many of the Arctic Security Cutters, the planned class of new medium icebreakers.

The U.S. Coast Guard is also tasked with supporting scientific research. Healy directly supports the National Science Foundation with her annual patrol. For research, the requirements are perhaps less stringent, as a pure research vessel can decide where it goes. A U.S. Coast Guard icebreaker conducting rescue and assist or breaking ice off of McMurdo has no such choice.

For the U.S. Coast Guard, polar icebreakers must be able to fulfill these roles/accomplish these missions now and in the future. For others, the required capabilities might be different.

This Lloyd’s Register chart (other classification societies have similar ones) lists some of the roles and functions of polar icebreakers. Vessels desiring an icebreaker designation must demonstrate that they can carry out their expected operational profile (i.e. their functions) in the planned operating area.

I think it is a useful framework to consider the roles of polar vessels, how they differ, and why all polar vessels are not suitable for all polar missions.

A Quick Note about the Icebreaker Designation:

Some sharp-eyed readers have probably noted that China’s polar research vessels are included in these charts/lists. In the past many (including me) have noted that China’s polar research vessels are just that- polar research vessels. They are not technically icebreakers.

The IACS Unified Requirements describe an additional “Icebreaker” notation that can be given to Polar Class vessels:

I1.1.3 Ships which are assigned a Polar Class notation and complying with the relevant requirements of UR I2 and UR I3 may be given the additional notation “Icebreaker”. “Icebreaker” refers to any ship having an operational profile⁴ that includes escort or ice management functions, having powering and dimensions that allow it to undertake aggressive operations in ice-covered waters.

Icebreaker notation requires an additional margin above that required by the Polar Class notation. None of China’s vessels have the additional ‘icebreaker’ notation.

I believe it is defensible to include China’s polar research vessels (along with other “non-icebreakers”) in these list as to exclude them would not reflect the true picture of global capabilities. After all, these Chinese research vessels support a large Antarctic presence and certainly have influence in the Arctic.

The Bottom Line:

While these charts and lists certainly have some utility in showing the capabilities of nations to operate in the ice, the challenging nature of counting icebreakers limits their usefulness in comparing fleet capability. As nations have different needs based on geography, it is far more useful to consider national requirements than to compare numbers.

U.S. Coast Guard Requirements:

The U.S. Coast Guard’s latest fleet analysis says that it needs eight or nine icebreakers, four or five of which should be heavy and four or five medium, in order to accomplish its required missions in the polar regions (both Arctic and Antarctic).

For refresher, here are two articles I’ve previously written about the importance of these missions in the Arctic and Antarctic. Both articles could use an update, but they remain useful in explaining why the U.S. Coast Guard needs a larger fleet to provide consistent presence in these regions:

It doesn’t matter how many icebreakers the Russians have in comparison to the U.S. Coast Guard. As a national with a long coastline above 60°N, Russia requires many more icebreakers than the United States to explore for oil/gas, support resupply (by sea) of their own cities, and to enable the export of key goods.

What matters is that the U.S. Coast Guard is unable to accomplish its assigned missions, putting at risk the ability of the United States to influence the situation in these two very important regions in the face of increased Russian and Chinese activity.

Thoughts and Comments:

Trying to get an apples-to-apples comparison between icebreakers and icebreaking fleets is surprisingly difficult, even impossible.

Different organizations use different methods in order to estimate the basic capability of nations to operate in ice. In general, looking at the numbers and capabilities of national fleets does show a level of interest in operations in the ice, whether driven by national ambition (such as China), necessity (such as Finland), or a combination of both (Russia).

Russia’s fleet is particularly hard to count, as demonstrated by the great variety of numbers cited in research papers and news articles (and in the three charts I used above). This is because Russia’s icebreaking ‘fleet’ contains a great variety of icebreaker types- from small port/coastal icebreakers to their powerful nuclear icebreakers. Drawing the line on “what is an icebreaker” can be challenging.

If one counts Russia’s smaller icebreakers, certainly Great Lakes icebreakers should also be included in the comparison, leading to a U.S. count of fifteen or sixteen instead of the three more commonly discussed. In my next article, I’ll describe those sixteen icebreakers to show the varying capability of vessels called “icebreakers.” At some point I will also dive into Russia’s icebreaking fleet, and deliver that promised ‘deep dive’ on China’s fleet of polar research vessels.

For that reason, the U.S. Governenment should focus on acquiring icebreakers to meet its requirements without worrying about the numerical differences.

As I write this there has been little no additional news on the USA-Finland deal for eleven Arctic Security Cutters, four of which are to be built in Finland. You can be sure I’m tracking that closely.

That’s it for today. Until next time—

All the Best,

PGR

1. For some reason, Aiviq did not receive a Polar Class designation even though her contract was signed after 2007. The American Bureau of Shipping classified Aiviq as an A3, roughly equivalent to PC3.

2. The Polar Class Rules are required by the International Maritime Organization’s (IMO) Guidelines for Ships Operating in Polar Waters. Specifically, they are applicable to “ships operating in Antarctic waters or while engaged in international voyages in Arctic waters.”

Antarctic waters are simply defined as waters south of 60° S:

For Arctic waters, it is a bit more complicated:

Because the requirements apply only to international voyages in Arctic waters, transits that fall only within Russian Arctic waters are excluded. The Russians have their own rules and classification system, the RMRS.

3. When I first began tracking icebreakers in 2017, the U.S. Coast Guard used icebreaker charts with this key for heavy/medium/light icebreakers.

4. Lloyd’s Register references three different functions in its July 2025 edition of Rules and Regulations for the Classification of Ships. From this, you can see that each function/profile could have different requirements to receive the “Icebreaker” designation. (Lloyd’s Register itself uses Icebreaker (+)). See function chart above.