Seasonal weather in the United States and Europe is heavily dependent on ocean currents in the North Atlantic, particularly the Gulf Stream, so it is important to understand these currents, their location, and what changes in them might mean for future weather and how they might affect winter climate.
This is the first article in our Gulf Stream series, taking a comprehensive look at this ocean current – where it is, how it works, and the important role it plays in winter weather in the U.S., Canada, and Europe.
What is the Gulf Stream?
The Gulf Stream is a powerful ocean current that carries warm water from the Gulf of Mexico into the North Atlantic Ocean. It travels up the east coast of the United States and then heads toward northwestern Europe.
Below is a quick overview of the North Atlantic Ocean Current and the Gulf Stream, showing how the Gulf Stream flows across the North Atlantic Ocean. The Gulf Stream doesn't flow in a neat straight line, but as you can see, it's much more complex and full of large and small whirlpools.
The warm waters of the Gulf Stream directly affect Florida's climate. Compared to other southeastern states, Florida has warmer winters and cooler summers.
The Gulf Stream also flows toward Europe, warming Western European countries and having a major impact on the regional climate.
The Gulf Stream is best understood through temperature analysis and sea surface movement. In the image below, you can see the sea surface temperatures in summer. You can see the current of warm water moving up along the east coast of the United States and extending into the North Atlantic Ocean.
This is the fully visible Gulf Stream, which carries vital warm water towards the northern regions of the Atlantic Ocean. In contrast, the cold Labrador Current can be seen flowing down along the east coast of Canada.
We've produced a high-resolution video animation showing the movement of the Gulf Stream, the warm water that flows along the East Coast of the United States throughout the year, keeping temperatures consistently warm even in winter.
The Gulf Stream is perhaps best viewed through an analysis of ocean surface motion and speed. In the image below, ocean surface currents are seen, where the Gulf Stream stands out most and where we can see its most vivid shape and morphology.
This current doesn't flow in a straight line as it appears in many diagrams. It's a much more complex flow with strong dynamics across the North Atlantic. It's filled with tiny eddies of warm and cold water. In fact, it's very similar to the jet stream we see in the atmosphere.
Looking around the world, we see that the Gulf Stream is not alone: in many regions, ocean circulation persists, the most notable example being perhaps the Japan Current (Kuroshio), whose activity is very similar to that of the Gulf Stream.
North Atlantic Current
The larger system that the Gulf Stream flows through is called the Atlantic Meridional Overturning (AMOC). The AMOC is a large system of currents in the Atlantic Ocean that is driven by differences in temperature and salinity, which affect density. The Gulf Stream is just the surface portion of the AMOC in the North Atlantic.
The image below, provided by the UK Met Office, gives a rough overview of the global ocean circulation system. This circulation system has many different names, but the most well-known is probably the “Earth Conveyor Belt” or “Thermohaline Circulation”. The AMOC is an ocean current system that covers the North and South Atlantic Oceans.
But what drives the North Atlantic ocean currents?
As the Gulf Stream carries the warm water north, it releases much of its heat and the water begins to cool. Along the way, evaporation also occurs, making the water saline.
Cold temperatures and high salinity make water denser and heavier, so this denser water begins to sink in the ocean. Sinking water creates movement and momentum, which pulls more water down from the surface, creating steady overturning currents.
The image below shows the salinity of the ocean surface, or the amount of salt in the water. The higher the number, the saltier and denser the water is. Above 35, the water still contains a lot of salt, so as it cools it becomes denser (heavier) and sinks farther out into the North Atlantic.
The cold, dense water slowly flows south for several kilometers below the ocean's surface. Eventually, the water begins to rise to the surface again, where it warms up in a process called upwelling, completing the cycle.
This is important because the AMOC is a vital component of Northern Hemisphere weather and climate. It transports a lot of warm water and energy northward. The image below outlines the North Atlantic portion of the AMOC, which also includes the Gulf Stream.
Below we have created a special graphic that shows why the Gulf Stream and ocean currents are so important to the weather in the United States, Canada, and Europe.
This image shows average January surface temperatures over the past 42 years, showing the large temperature differences between the far North Atlantic and Canada, for example, despite being at the same latitude.
For example, look at the 60th parallel along the tip of Greenland. You'll see that there's a difference of nearly 30 degrees Celsius between the North Atlantic and southern Canada. Further north, the temperature difference is just as great.
The difference in winter climate between Britain and southern Canada is quite striking. This difference would not occur without the warm Gulf Stream, which brings warm water north and keeps Europe's climate moderate.
Since many of our readers are familiar with the Fahrenheit temperature scale, we've created the same graph in Fahrenheit. You can see that there is a large difference of 50-60 degrees Fahrenheit between the far North Atlantic and southern Canada.
Also, warmer weather is seen along the east coast of the United States, again due in part to the influence of warm ocean currents, which bring about moderate weather. The Gulf Stream brings warmer waters and temperatures, which also influences summers and thunderstorm activity.
A closer look at the North Atlantic edge of the AMOC shows that it is extremely complex, with warm water being transported far beyond the British Isles and Iceland, reaching deep into the Arctic Circle.
Looking at actual ocean temperatures from last February, we can see that positive temperatures of 6-10 degrees (43-50 degrees F) continued all the way to the Arctic Circle. The dark blue temperatures indicate sea ice. We used data from winter (February) because that is when the temperature difference is greatest and is most visible as warm ocean currents are more prominent.
Looking deeper, about 380 meters (1,240 feet), the Gulf Stream is still clearly visible, but the cold waters south of Greenland, which sink as the current thickens, are also more visible.
Continuing down, you reach the bottom of the Gulf Stream at a depth of about 1,200 meters (4,000 feet). To the east, near the European continental shelf, the waters are warmer and there is no noticeable warm current.
Recent studies and data show that the Gulf Stream is indeed losing momentum and starting to collapse. In our next article on the Gulf Stream, we will look at the changes in the Gulf Stream and why and how it is collapsing. Don't forget to bookmark this page to learn more about weather and climate.
