If the Great Lakes are directly connected to the Atlantic Ocean, what prevents them from being saltwater lakes?

The Great Lakes are indeed directly connected to the Atlantic Ocean, via the Saint Lawrence River, which flows from Lake Ontario to the Gulf of Saint Lawrence, and from there to the Atlantic Ocean. However, the Great Lakes are not saltwater lakes because of the following reasons:

• Location: The Great Lakes are located inland, far from the coast, and are fed by freshwater rivers and streams. This means that they do not have a direct source of saltwater.
• Outflow: While the Great Lakes do have an outflow to the Atlantic Ocean, it is not a large enough volume of water to significantly impact the salinity of the lakes. In addition, the lakes lose water through evaporation, which concentrates the remaining water and increases its salinity, but this is countered by the constant input of freshwater from the rivers and streams.
• Ice Cover: The Great Lakes are located in a cold climate and are often covered by ice in the winter months. This ice cover prevents the lakes from evaporating too much, which could lead to an increase in salinity.

Overall, while the Great Lakes are connected to the Atlantic Ocean, their location, outflow, and ice cover prevent them from becoming saltwater lakes.