Key takeaways
- Fjords are glacial valleys drowned by the sea, which is why they are so much deeper than a river valley of the same size.
- A fjord basin can be several hundred metres deep while the sill at its mouth is far shallower, trapping cold water inside.
- That geometry is why a boat can work here in an Arctic winter when the open sea outside would be impossible.
- Cold deep basins with soft seabed give the king crab the invertebrates and detritus it feeds on.
What a fjord actually is
The word gets used loosely for any dramatic inlet, and the real definition matters here because it explains everything about the water you sail through. A fjord is a glacial valley that has been drowned by the sea. Ice, not a river, cut it, and ice cuts differently.
A river erodes downward in a V, wearing at the lowest point of its channel. A glacier is a body of ice hundreds of metres thick that scours the whole valley floor and both walls at once, producing a U-shaped trough with steep sides and a broad flat bottom. When the ice retreated and sea level rose, the sea flooded those troughs. What you are sailing along is the bottom of an ice-age valley.
Why they are so deep
Because a glacier does not stop cutting at sea level. It has enormous weight behind it and it keeps grinding downward for as long as it is moving, which means the floor of a fjord basin can lie hundreds of metres below the surface, considerably deeper than the open coastal shelf just outside.
There is usually a shallower sill at the mouth, where the glacier finally lost its power and dumped the rock it had been carrying. That sill is why fjord water behaves the way it does. Cold, dense water gets trapped in the basin behind it and does not exchange freely with the open sea, which makes a fjord basin a cold, stable, dark environment year round.
The snow-covered fjord landscape outside Tromso from the deck
Why the crab is down there
Everything above is the reason a king crab does well here. It is a cold-water animal that lives on the seabed, feeding on invertebrates, molluscs, worms and detritus, and it does not need light. A deep fjord basin with a soft floor and cold stable water is close to ideal ground for it.
The pots go down into exactly that environment. When you watch one come up over the rail, what you are seeing is a sample of a world a few hundred metres below the boat that has almost nothing in common with the bright snowy landscape you are looking at while you wait.
The shelter that makes winter work
The other consequence of the geometry is protection. The islands and headlands around Tromso break up the swell coming in off the Norwegian Sea, and the fjords themselves are enclosed on both sides by mountain. The result is water that stays workable in weather that would stop a boat outside.
That is not a small thing for a cruise that sails year round. An operator running an open-coast trip in January would be cancelling constantly. Working inside the fjord system means the trip can be a dependable daily sailing rather than a seasonal one, which is precisely what this cruise is.
2h
Roughly how much of the four and a half hours is spent under way, which is the time you get to look at the fjords.
The islands you pass
Tromso itself sits on an island, Tromsoya, with the city built across it and bridges connecting it to the mainland on one side and to Kvaloya, the much larger whale island, on the other. The sailing takes you out through that channel system rather than straight out to sea.
What you get from the deck is a sequence: the city and its cathedral, then bridges, then the shoulders of the islands rising on either side, then progressively wilder ground as the settlements thin out. The mountains do not look like the western fjord country of postcards; they are lower, more rounded and more scattered, and in winter they are white from the water up.
How the mountains got there
The rock is far older than the fjords and comes from an entirely different event. These mountains are the worn-down roots of the Caledonian range, thrown up when continents collided several hundred million years ago in a mountain-building episode that also produced the Scottish Highlands and the Appalachians.
What you see now is the eroded stump of something once far higher. Then, comparatively recently, the ice arrived and carved the valleys through it. Two processes, hundreds of millions of years apart, and the landscape you are sailing through is the result of both working on the same rock.
What it looks like in each season
In deep winter the whole thing is white to the waterline, and in December and January the light is a long blue twilight rather than daylight. That is a genuinely strange and beautiful thing to move through, and it is why some photographers deliberately pick those months.
By spring the low sun comes back and lights the snow directly, which is arguably the best of it. In summer the mountains are green and brown with snow only on the tops, the water turns a different colour entirely, and the whole scene stays lit around the clock. The same two hours of sailing gives you a completely different landscape depending on when you come.
It is worth spending the sailing time on deck for at least part of it, whatever the month. The saloon is warm and the windows are good, but the scale of a fjord does not come across through glass, and the two hours under way are not a commute to the crab. They are half of what you paid for.
