Both the atmosphere and oceans play significant roles in the determination of climate on seasonal and longer time scales. Due to latitudinal differences in solar heating, the Tropics have a net energy surplus whereas the polar regions have a net energy deficit. Thus water is relatively transparent to solar radiation, meaning it is an excellent absorber of solar radiation. This is because the absorption of solar radiation is not limited to the surface but can occur through a volume of water down to a depth of about 100 m.
Oceans receive more than half of the energy entering the climate system.
The ocean has a high heat capacity. The tropical oceans are particularly large reservoirs of heat. Oceans provide the bulk of the thermal inertia of the climate system on the time scale of weeks to centuries. The ability of the oceans to store heat reduces the magnitude of the seasonal cycle in surface temperature by storing heat in summer and releasing it in winter. The moderating effect of oceans on air temperature occurs because of the thermal storage in the upper layers of the ocean.