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Place 07 · The Northeast Coast · Chapter 3 of 7
Where Warm Meets Cold
Off Cape Hatteras, a river of warm tropical water carrying more than all the world’s rivers combined turns away from the coast and heads for Europe, and the cold water from Labrador slides in to take its place.
About 15 minutes · 1 video · 1 live ocean map · 2 quick activities
Start here
The Kuroshio’s Atlantic twin
In Place 06 you met the Kuroshio, the fast, narrow, warm current on the western side of the North Pacific gyre. The Atlantic has its own: the Gulf Stream, a western boundary current that runs north along Florida and the Carolinas, then turns east off Cape Hatteras, North Carolina, and heads across the ocean. North of that turn, the Northeast coast is bathed by something else entirely: cold water that started near Greenland and Labrador.
Watch this
See it move
Met Office — What is the Gulf Stream and why is it important? Under two minutes from the UK’s national weather service, who have a keen personal interest in warm water arriving from America.
While you watch, look for
- Where the Gulf Stream starts and where it goes
- Why people on both sides of the Atlantic care about it
- Something you did not expect. Hold onto it.
The short version
Three things going on here
The warm side
A fast river in the sea
NOAA puts the Gulf Stream’s average speed at about 6.4 km/h (4 mph), reaching about 9 km/h near the surface, and says it carries more water than all the world’s rivers combined. It hugs the coast up to North Carolina, then peels away to the northeast off Cape Hatteras and slows to about 1.6 km/h as it widens. Everything from Delaware Bay north sits on the other side of that turn.
The cold side
Water from Labrador
The Labrador Current flows south along the coast of Labrador and Newfoundland at about 35 km a day, carrying icebergs as far as the Grand Banks. It keeps the water over the shelf there 7 to 10°C colder than at the same latitude on the west coast of Europe. Cold water that ultimately comes from the north helps keep New England’s sea chilly, and every summer a band of cold bottom water called the Cold Pool lingers under the warm surface from Cape Hatteras to Georges Bank.
The front
Rings, eddies and fog
Where warm and cold water meet there is a front, a sharp boundary where the temperature changes quickly over a short distance. The Gulf Stream wiggles, and its loops can pinch off as warm-core rings: spinning, clockwise blobs of warm water that drift for months, and a 2020 census counted about 33 a year since 2000, up from about 18 a year before. When warm, moist summer air drifts over the cold water off Maine, it chills until its water vapor condenses into fog, which is why so many Maine lighthouses come with foghorns.
Photos: Zelch Csaba, Jonathan Cooper, Shamia Casiano / Pexels
Play with it
Find the line between warm and cold
This live map shows today’s sea surface temperatures and currents off the East Coast, from Cape Hatteras to Nova Scotia. Find the fast, warm streak leaving the coast at North Carolina, then look north of it for the cold water along New England, and click anywhere to read the temperature.
Live map: earth.nullschool.net by Cameron Beccario, with sea surface temperatures from NOAA and ocean currents from OSCAR (Earth & Space Research) and the Copernicus Marine Service.
Two questions to answer while you are in there
- Click on the Gulf Stream south of Cape Cod, then on the water just off the coast of Maine. How big is the temperature difference today, and how far apart are the two spots?
- Can you find a loop or a round blob of warm water that seems to have broken off the Gulf Stream? Which way do you think it is spinning?
Try it yourself
Check yourself
Try it
Warm Side or Cold Side?
Eight quick calls: which side of the front are you on?
Try it · interactive
Current Collision
Build a map and cross-section from Cape Hatteras to Nova Scotia: switch the Gulf Stream and the Labrador Current on and off, read the temperature along a ship’s route, spin off a warm-core ring, and see where the fog forms.
Open Current Collision in its own window (opens in a new tab).
Words you will hear
Four terms, that is all
Gulf Stream
Fast, warm western boundary current of the Atlantic
Labrador Current
Cold current flowing south past Labrador and Newfoundland
Front
Sharp boundary between two different water masses
Warm-core ring
Spinning warm eddy pinched off the Gulf Stream
Check your understanding
Practice the whole chapter
Everything in this chapter, in eight quick questions. Retry as often as you like. Read the feedback on every answer, right or wrong, because that is where the learning is.
Practice
Practice: Where Warm Meets Cold
Eight questions covering the video, the three cards, the four terms and the interactive above.
If you want more
Go deeper
- Oceanography 101 (MiraCosta) 9.8 — The Gulf Stream and the Antarctic Circumpolar Currents — LibreTexts · 5 minutes
- Webb 9.4 — Western Intensification — LibreTexts · 6 minutes
- NOAA National Ocean Service — How fast is the Gulf Stream? — NOAA · 2 minutes
Photo credits (Pexels): Brian, Karolina, Zelch Csaba, Jonathan Cooper, Shamia Casiano.