Atlantic storms mix the surface layer of the ocean
Westward moving weather systems in the mid-latitudes can dramatically disturb the ocean’s upper layers. These storms move very quickly, much more quickly than oceanic eddies in deeper layers. They thus increase the amount of mixing in the upper layers of water, leading to homogeneous conditions in the so-called surface mixed layer (causing more uniform temperature and salt concentrations, for example). The more mixing that takes place at the surface, the more homogeneous and thick this layer becomes.
The animation shows the fluctuations of the ocean’s surface mixed layer: The color scale reflects the thickness of the layer. The red colors reflect particularly thick layers, while the bluish colors indicate thinner uniform layers. The strongest variations in the northern hemisphere are apparent between January and March. In contrast, layering appears relatively stable between May and September.