Thermoclines occur in tropical, equatorial seas and lakes but never in polar seas. This absence of thermoclines near the poles is the result of water circulation patterns and low levels of sunlight. The solar energy entering polar waters is not enough to raise the surface temperature significantly. Without this warm top layer, a thermocline cannot form. Also the positions of land masses in the polar latitudes cause strong circumpolar ocean currents that would disrupt any thermocline formation.