Melt butter in a small saucepan over medium-low heat; stir maple syrup, curry powder, and ground mustard into butter until smooth. Pour 1/4 cup ginger ale into butter mixture. Reduce heat to low and simmer for 2 minutes.

Place pork tenderloin into a slow cooker and spread carrots over pork; pour remaining ginger ale over meat and carrots. Pour the butter syrup over the top.

Cover and cook on Low for 8 hours. Season with salt and black pepper.