What is the name of the currents that flow in the opposite direction to the main surface currents?

Countercurrents are ocean currents that move in the opposite direction to the prevailing surface currents. These currents are often found beneath the main surface layer and can play a significant role in oceanic circulation. They can be influenced by various factors, including wind patterns, temperature, salinity differences, and the Coriolis effect.

Countercurrents can significantly impact marine ecosystems by facilitating the mixing of nutrients and playing a role in the distribution of marine species. Their existence is crucial for understanding the overall dynamics of ocean circulation, as they contribute to the redistribution of heat and nutrients throughout different layers of the ocean.

The other options describe different types of currents; for example, undercurrents describe currents that flow beneath surface currents but do not specifically denote the reverse flow relative to main currents. Tidal currents are related to the gravitational pulls of the moon and sun and are periodic, while thermohaline currents are driven by differences in temperature and salinity rather than the direct opposition to surface currents.