What characteristic can contribute to the complexity of a wine when blended?

The characteristic that contributes to the complexity of a wine when blended is barrel aging. This process allows wine to interact with the wood, which can impart various flavors and aromas such as vanilla, spice, and toast. Additionally, barrel aging can encourage certain chemical reactions that enhance the wine's structure and mouthfeel. This interplay of flavors from oak and the wine itself plays a significant role in creating a more nuanced and layered tasting experience, enhancing the overall complexity of the final product.

While consistency, flavor intensity, and alcohol content are important aspects of wine, they do not specifically contribute to the depth and intertwining flavor profiles that blending with barrel aging can bring to a wine.