In the Great Lakes, there are permanent currents and variable currents. Permanent currents are always found in certain locations — and only vary in strength. For example, strong currents are always present along piers and breakwalls, and can be found where rivers and streams empty into the lake.

Yes, absolutely. The Great Lakes have currents that are remarkably similar to those in the world’s oceans, though on a smaller scale. These currents are a critical part of the lakes’ physical dynamics, influencing everything from water temperature and nutrient distribution to navigation, pollution dispersal, and beach safety.

Here’s a breakdown of the main types of currents found in the Great Lakes:

1. Wind-Driven Currents (The Most Common)

These are the primary drivers of surface water movement. How they form: Sustained winds blowing over the vast surface of a lake push the water, creating currents that flow primarily in the direction of the wind. Impact: They can cause upwelling (when wind pushes surface water away, allowing colder, nutrient-rich water from the depths to rise) and downwelling. They are also responsible for seiches (see below).

2. Thermal Currents

• How they form: In summer, shallow coastal waters warm up much faster than the deep, central lake. This warmer, less dense water can flow offshore, while cooler water from the depths moves in to replace it near shore, creating convection-like currents.

3. Density Currents

• How they form: Caused by differences in water temperature and sediment load. For example, a river (like the St. Clair River flowing into Lake St. Clair) may carry colder or sediment-laden water that is denser than the lake water. This denser water can plunge beneath the surface and flow along the lake bottom as a distinct current.

4. Wave-Induced Currents

These are critical for beach safety: Longshore Currents