LNG Chain

Explainer

Ice-class carriers and the Arctic routes

An ice-class LNG carrier is a vessel strengthened to operate independently in sea ice, the highest commercial grade being Arc7 ships able to break ice astern, built to serve Arctic export projects along the Northern Sea Route.

Arctic LNG projects present a problem no other export scheme has: for part of the year, the sea between the plant and the customer is solid.

What ice class means

Ice classes are notations assigned by classification societies describing what conditions a hull and its machinery can handle. They run from light notations for occasional first-year ice up to grades intended for independent operation in substantial ice.

For LNG the notation that matters commercially is Arc7, under the Russian system. It denotes a vessel able to work in significant first-year ice on its own for much of the year rather than following an icebreaker throughout. That independence is the whole point: escorting a fleet of gas carriers with dedicated icebreakers around the calendar would be prohibitive.

The double-acting design

An efficient open-water hull and an efficient icebreaking hull are close to opposites. Open water wants a fine bow that parts water cleanly. Ice wants a blunt, sloped form that rides up on the sheet and breaks it by weight.

The double-acting solution is to stop choosing. The ship runs bow-first in open water, and turns around in heavy ice to run astern, where the hull form and the azimuth propulsion pods are arranged to break it. The pods swivel, so the ship is genuinely bidirectional rather than merely able to reverse.

It is an elegant answer to a hard constraint, and it requires far more installed power than a conventional carrier — a substantial share of the extra cost, along with the strengthened structure and winterisation of every system exposed to the weather.

The route is a season, not a distance

The Northern Sea Route across the top of Russia is dramatically shorter between north-west Europe and north-east Asia than any southern alternative, and it avoids Suez, Malacca and the Panama Canal entirely.

It is also only usable part of the year. Eastbound transits have historically been concentrated in the summer and autumn, and while the window has lengthened it has not become a year-round shipping lane. Outside the season, cargoes from Arctic projects go west instead, or are transshipped to conventional vessels at an ice-free port so the expensive ice-class ships can shuttle rather than make the full voyage.

That seasonal switching is unusual. Most LNG trades have a route; an Arctic trade has two, and which one is in use changes the voyage length, the number of ships required and the effective capacity of the fleet serving the project.

Transshipment

Because ice-class vessels are expensive and slow in open water relative to their cost, the economic pattern is to use them for the ice leg only. A cargo is carried out of the Arctic to a transshipment point and moved ship to ship into a conventional carrier for the long haul.

It adds an operation, a cost and a place where things can go wrong, and it is done anyway because the alternative is sending a ship built for ice across an ocean that has none.

Reading Arctic projects in the tracker

Arctic export terminals appear in the data like any other, with capacity, status and ownership. What the data cannot show is the seasonal structure behind them: a project whose deliverability depends on the ice year, a fleet that is purpose-built and not fungible with the rest of the world’s ships, and a route whose length depends on the month.

The carrier section would be where those vessels appear, and it is currently empty because Global Energy Monitor publishes the LNG Carrier Tracker only behind a download form. Until that file is loaded, the ships serving these projects are absent from the site even though the terminals they serve are not.

Common questions

Each answer stands on its own.

What does Arc7 mean?
The highest ice class commonly applied to LNG carriers under the Russian Maritime Register system, denoting a vessel able to operate independently in substantial first-year ice rather than needing an icebreaker escort throughout.
What is a double-acting ship?
A vessel designed to run bow-first in open water for efficiency and stern-first through heavy ice, where the hull form and the propulsion pods are arranged to break it. It avoids compromising open-water performance for ice capability.
Is the Northern Sea Route open all year?
No. Eastbound transits are seasonal, historically concentrated in the summer and autumn months, though the window has lengthened. Outside it, Arctic cargoes go west or transship, which changes voyage length dramatically.
Why do ice-class carriers cost so much more?
A strengthened hull, far more installed power, azimuth propulsion pods and winterised systems throughout. The vessels are also built in small series at few yards, so there is little of the cost learning that a long production run brings.
Does ice class affect cargo capacity?
Yes, indirectly. Structure and machinery take space and weight, so an ice-class vessel typically carries somewhat less cargo than a conventional ship of similar dimensions.

Last reviewed 2026-09-07.