Seasonal weather in the United States and Europe depends strongly on the North Atlantic Ocean currents, specifically the Gulf Stream. For that reason, it is important that we understand these currents, where they are, and what their changes mean for our weather in the future and their influence on the Winter climate.
This is the first article of the Gulf Stream series, where we will look at this ocean current as a whole: where it is, how it works, and what important role it plays in the Winter climate over the United States, Canada, and Europe.
WHAT IS THE GULF STREAM
The Gulf Stream is a powerful ocean current that brings warmer waters from the Gulf of Mexico into the North Atlantic Ocean. It extends upwards along the eastern coast of the United States and then turns towards northwest Europe.
Below, you can see a simple outline of the North Atlantic ocean currents, and the Gulf Stream. You can see how it flows across the North Atlantic. It does not flow in such a nice straight line, but as you will see, it is much more complex and full of small and large swirls.
The warmer waters of the Gulf Stream directly influence the climate of Florida. Compared to other southeastern states, it keeps Florida’s temperatures warmer in the winter and cooler in the summer.
Since the Gulf Stream also extends towards Europe, it helps to warm western European countries, having a major impact on the regional climate.
The Gulf Stream is best seen if we look at the temperature analysis and the ocean surface movement. In the image below, you can see the ocean surface temperature in summer. You can see the warm stream of water moving up along the eastern coast of the United States, extending far into the North Atlantic.
This is the Gulf Stream fully visible, transporting essential warmer waters up towards the northern regions of the Atlantic Ocean. In contrast, you can see how the cold Labrador Current flows down along the east Canadian coast.
We produced a high-resolution video animation that shows the Gulf Stream in motion. The warm waters flow up along the east coast of the United States throughout the year, keeping steady warm temperatures even during the winter.
The Gulf Stream is perhaps best seen in the movement and speed analysis of the ocean surface. In the image below, you can see the ocean surface current speed, where the Gulf Stream really stands out and can be seen in its most raw shape and form.
This ocean current does not flow in a straight line, as seen in many diagrams. It is much more complex, with strong dynamics across the North Atlantic. It is full of smaller swirls of water, both warm and cold. It is actually very similar to the jet stream found in the atmosphere.
Looking around the world, we can see that the Gulf Stream is not the only one of its kind. Many areas have persistent ocean circulation. The most notable example is perhaps the Japan Current (Kuroshio), which is very similar to the Gulf Stream in its activity.
NORTH ATLANTIC OCEAN CURRENTS
The larger system in which the Gulf Stream flows is called the Atlantic Meridional Overturning Circulation, or AMOC. The AMOC is a large system of ocean currents in the Atlantic Ocean, driven by differences in temperature and salt content, which affects its density. The Gulf Stream is just the surface part of the AMOC in the North Atlantic.
The image below from the UK Met Office shows a rough outline of the entire global ocean circulation system. It has many different names, but perhaps the most notable are the Global Conveyor Belt or the Thermohaline Circulation. AMOC is the ocean current system that covers the North and South Atlantic.
But what is driving the ocean currents in the North Atlantic?
As the Gulf Stream transports warm waters northwards, it starts to cool, as it releases a large part of the heat. Evaporation also occurs along the way, increasing the salt concentration in the ocean.
Lower temperatures and a high salt content make the water denser and heavier, so this dense water will start to sink down into the ocean. Sinking water causes movement and momentum, pulling down more water from the surface and creating a stable overturning flow.
The image below shows ocean surface salinity or the amount of salt in the water. The higher the number, the saltier and denser the water. Above 35, we still have salty waters, so as the water cools, it gets denser (heavier) and sinks down in the far North Atlantic.
The cold, dense water slowly flows southwards, several kilometers below the ocean surface. Eventually, it starts to rise back to the surface and warms in a process called “upwelling.” With that, the circulation is complete.
This is important because the AMOC is an essential part of the weather and climate in the Northern Hemisphere. It transports a lot of warmer waters and energy towards the north. The schematic below shows the outline of the North Atlantic part of the AMOC, of which the Gulf Stream is a part.
We produced a special graphic below that shows why the Gulf Stream and Ocean currents are so important for the weather in the United States, Canada, and Europe.
The image shows the average January surface temperature for the past 42 years. It shows the large temperature difference between the far North Atlantic and Canada, for example, despite being at the same Latitude.
We can look at the latitude line 60 degrees North, for example, along the tip of Greenland. You can see that there is almost a 30°C difference between the North Atlantic and southern Canada. Going further North, the temperature difference is just as large.
The difference in winter climate between the United Kingdom and southern Canada is really significant. This would not be possible without the warm Gulf Stream, as it brings warmer waters towards the North, keeping the climate milder in Europe.
Since many of our readers are more familiar with the Fahrenheit temperature scale, we produced the same graphic, but in Fahrenheit degrees. You can see the large 50-60 degrees F difference between the far North Atlantic and southern Canada.
You can also see the warmer climate along the east coast of the United States. This is also partially affected by the warm ocean current, which brings milder conditions. The Gulf Stream also has an effect in summer and on thunderstorm activity, as it provides warmer waters and air temperature.
Looking closer at the far North Atlantic part of the AMOC, we can see that it is very complex. Warmer waters are being transported far beyond the British Isles and Iceland, reaching deep into the Arctic Circle.
Looking at the actual ocean temperatures from last February, you can see positive temperatures of 6-10 degrees C (43-50 degrees F) reaching into the Polar Circle. Dark blue temperatures indicate sea ice. We used the winter (February) data because the temperature contrast is greatest in winter, and the warm ocean currents are best seen as they stand out more.
If we look deeper down below the surface, at around 380 meters (1240ft), the Gulf Stream is still quite obvious. But you can also better see the colder waters south of Greenland, where the ocean current sinks down as it becomes denser.
Still going further down, to around 1200 meters (4000ft), we reach the very bottom of the Gulf Stream flow. We can hardly see the warm current standing out, as we have warmer ocean temperatures further towards the east, around the European continental shelf.
Recent studies and data show that the Gulf Stream is actually losing strength and is starting to collapse. In our next article on the Gulf Stream, we will look at the changes in the Gulf Stream and how/why it is collapsing. So don’t forget to bookmark our page to learn more about our weather and climate.