The Labrador Current is a cold, relatively fresh current that flows south along the coast of Labrador and eastern Newfoundland, carrying Arctic water out of Baffin Bay and the Davis Strait into the North Atlantic. By the standards of the great boundary currents it is small — transport of a few sverdrups against the Gulf Stream's 150 — but its influence is out of all proportion to its size, for three reasons. It carries icebergs, calved mostly from the glaciers of west Greenland, south into the busiest transatlantic shipping lanes, in the stretch of ocean known as Iceberg Alley. Where it meets the Gulf Stream near the Grand Banks it produces one of the sharpest temperature fronts in any ocean, the cold wall, and some of the densest and most persistent fog anywhere on Earth. And the mixing at that boundary, over a shallow submarine plateau, created the Grand Banks — for four centuries the most productive fishing ground in the world, until the cod collapsed in 1992.
Down From Baffin Bay
The current is assembled from two cold sources. The larger is the Baffin Island Current, carrying Arctic water south through Baffin Bay and the Davis Strait. The other is the West Greenland Current, running up Greenland's west coast and then curving west across the top of the Davis Strait to join the southward flow.
What results is water that is both cold and fresh: temperatures from below zero to about 4 °C, and salinity noticeably lower than the open Atlantic, because it carries Arctic river runoff, sea-ice melt and Greenland meltwater. The freshness matters more than it might seem, because fresh water is light, and light water does not sink. That has consequences discussed below.
The current follows the Labrador shelf south, splits around the Grand Banks, and sends one branch through the Strait of Belle Isle into the Gulf of St Lawrence and another around the outside of the Banks. Its cold water reaches as far south as the latitude of New York on the inshore side of the Gulf Stream, which is why the sea off Nova Scotia and Maine is so much colder than the sea at equivalent latitudes in Europe. Its northern reaches are covered in the Labrador Sea guide.
Iceberg Alley and the Ice Patrol
Roughly 10,000 to 40,000 icebergs calve from Greenland's glaciers each year, most from the fast-flowing outlet glaciers of the west coast. The Labrador Current is what moves them.
The journey takes one to three years. Bergs drift north up Greenland's west coast, cross to the Canadian side, and then head south, running aground repeatedly on shallow banks along the way and often spending a winter locked in sea ice. Those that survive reach the latitude of Newfoundland in spring and early summer, and the stretch of water off eastern Newfoundland where they concentrate is Iceberg Alley. In an average year a few hundred cross 48°N, the latitude at which they become a shipping hazard; in a heavy year, over a thousand.
They are lethal because they arrive exactly where the great-circle route between northwestern Europe and the northeastern United States runs, and because they arrive in fog. The Titanic struck one on 14 April 1912 in calm, clear, moonless conditions with a flat sea — a combination that removed the usual visual cue of surf breaking at a berg's waterline. The response was the International Ice Patrol, established in 1914 and still operating, now flying aerial reconnaissance and combining it with satellite data and drift modelling to issue daily ice limits. No vessel heeding the published limit has been lost to a berg since.
The Cold Wall
Just southeast of the Grand Banks, the Labrador Current runs into the Gulf Stream, and the meeting is abrupt rather than gradual.
The temperature difference across the front can exceed 15 °C over a horizontal distance of a few kilometres — one of the steepest gradients in any ocean. Eighteenth-century navigators used it as a positioning aid: a thermometer over the side told you which side of the front you were on, and therefore roughly where you were, long before reliable longitude was available.
The fog is a direct consequence. Warm, humid air sitting over the Gulf Stream drifts north across the cold Labrador water, is chilled from below, and its moisture condenses. The result is advection fog on an enormous scale, and the Grand Banks are among the foggiest places on the planet: parts of the area average over 120 days of fog a year, and Argentia in Newfoundland has recorded more than 200. Fog and icebergs in the same water, on the same shipping route, in the same season, is the combination that made this stretch of ocean so dangerous.
What the Icebergs Are Worth
An unusual set of industries has grown up around the ice the current delivers, on the reasonable grounds that if several hundred icebergs a year are going to arrive off your coast and melt, you may as well use them.
Newfoundland operators harvest bergs commercially, working from small boats with nets and chainsaws or collecting the growlers and bergy bits that break off, and the water is sold for bottled water, vodka, gin and beer. The selling point is genuine: the ice fell as snow on Greenland tens of thousands of years ago and compacted without ever touching the ground, so it contains almost no dissolved minerals and traps air bubbles at the pressure of the ancient atmosphere. Poured into a glass, it fizzes faintly as those bubbles release.
Iceberg tourism is larger. The bergs grounded along the Newfoundland and Labrador coasts each spring draw a substantial visitor season, tracked by a public iceberg-sighting map, and the towns along the northeast coast plan around it much as Tasmania plans around the aurora.
Then there is the industry that pays to keep them away. Oil and gas platforms on the Grand Banks — Hibernia, Terra Nova, White Rose — sit directly in Iceberg Alley, and they have to manage the hazard actively. Hibernia's concrete gravity base structure was engineered with a serrated outer wall designed to withstand a direct strike from a large berg. Smaller bergs are dealt with by physical intervention: support vessels tow them aside with looped cables or steer them off course using propeller wash and water cannon. Iceberg management is a permanent, budgeted line item on the Newfoundland offshore, and it exists because of a current that is mostly notable for being small.
The Grand Banks and the Collapse
The Grand Banks are a series of shallow submarine plateaus southeast of Newfoundland, in places under 50 metres of water. Two things made them extraordinarily productive: sunlight reaching the seabed across a huge area, and the nutrient supply generated where the two currents meet and mix.
Atlantic cod were the result, in quantities that European fishermen found difficult to describe. Basque, Portuguese, French and English fleets were working the Banks by the early sixteenth century, and salt cod from Newfoundland became a staple commodity of Atlantic trade for four hundred years. The fishery survived that entire period on hook, line and small boats.
It did not survive industrial trawling. Factory freezer trawlers arriving from the 1950s took catches an order of magnitude larger, landings peaked around 1968, and the stock declined through the 1970s and 1980s while quotas were repeatedly set above scientific advice. In July 1992 Canada declared a moratorium on northern cod fishing. It ended a five-century industry effectively overnight and put tens of thousands of Newfoundlanders out of work — the largest single industrial layoff in Canadian history.
Three decades on, recovery has been slow and partial. The ecosystem reorganised, with capelin, shrimp and snow crab occupying space the cod had held, and the cod that remain grow more slowly and mature smaller. It is the standard reference case for the proposition that a fishery can be pushed past a point from which it does not simply spring back.
A Freshening Current, and Why It Matters
The Labrador Current is getting fresher, and this connects a small regional current to a question of global consequence.
The Labrador Sea is one of a handful of places on Earth where surface water becomes dense enough to sink to great depth in winter — deep convection, the process that forms the dense water filling the deep Atlantic and drives the lower limb of the overturning circulation. That process requires surface water to be salty enough that winter cooling can tip it over.
Greenland is now losing mass at a substantial rate, and much of the resulting fresh water enters exactly this region. Fresh water is buoyant, and a fresher surface layer resists sinking regardless of how cold it gets. Observations have recorded significant freshening, and winters with little or no deep convection in the Labrador Sea have been documented.
The stakes are set out in the guides to the Gulf Stream and the North Atlantic Drift: if the northern end of the circulation stops sinking, the whole conveyor slows. Whether Labrador Sea convection is genuinely on a downward trajectory or simply passing through a long phase of natural variability is one of the more consequential open questions in oceanography, and it is being asked about a current whose transport is smaller than a single Gulf Stream ring.