What action should you take to manage carburetor icing once it's indicated?

The correct action to manage carburetor icing once it’s indicated is to turn on carburetor heat. Carburetor icing can occur when the temperature and humidity conditions are conducive to ice formation in the carburetor, which can disrupt the airflow and fuel flow to the engine. When carburetor heat is activated, it introduces warm air into the carburetor. This warm air helps to melt any ice that has formed and prevents further ice from forming, thereby restoring normal operation of the engine.

Turning on carburetor heat is a critical response that directly addresses the cause of the problem. The other options, such as increasing throttle or adjusting the mixture to lean, do not directly counteract the icing effect and may even exacerbate the situation by increasing the risk of engine roughness or further complications. Climbing to a higher altitude may also not resolve the icing issue since temperatures can still support icing at higher elevations. Thus, using carburetor heat is the most effective and immediate action to take in managing carburetor icing.