Although there are several factors that determine the intensity of this current, we generally speak of two main factors. One of the factors that drive the water flow is the process that occurs when the cold air in the Norwegian Sea, and the surrounding cold Arctic water is mixed with the warm water and cools it. The cold water then becomes heavy and sinks towards the bottom, where it then flows back into the North Atlantic as a bottom current. This process "draws" the warm and salty Atlantic water into our region and supports a warmer climate in northern Europe than is normal at such high latitudes.
The global temperature increase will eventually lead to an increased melting of polar ice. This will form a layer of fresh water on the ocean surface, a layer that is lighter than the salty Atlantic water. This fresh water will work as an insulating cover over the Atlantic water. The consequence of this will be that the Atlantic water is not cooled sufficiently to sink down and form deep water. This slows the process that "draws" the warm Atlantic water up to our latitudes, and we can get a colder climate. This hypothesis is supported by the fact that we have observed a reduction in the formation of heavy deep water in the Norwegian Sea during the past 30 years, although the process is far from being stopped.
The other important driving force is the general wind patterns over the North Atlantic. Low pressure systems keep coming in over the Norwegian coast from the southwest, will also contribute to push the warm Atlantic current into the Norwegian Sea.
This is the wind-driven component that feeds the strength of the ocean currents. We can say that this process "pushes" the warm and salty water into our oceans. As a result of global warming we are experiencing stronger wind activity in our area, which is also observed in the past 30 years. Thus, the second of the two major driving forces of the North Atlantic current has the complete opposite effect than the first