11.8: The Importance of the Ocean’s Seasonal Cycle

The seasonal cycle of stratification and destratification drives some of the most important processes in the ocean. Seasonal production of cold water at the surface in polar oceans plays a key role in the formation of deep and abyssal waters, critical to the deep ocean circulation. The seasonal cycle of primary production in temperate and polar oceans nourishes marine food webs and supports fisheries. And the seasonal growth and decay of the polar ice caps has profound implications for a number of physical, chemical, and biological processes as well.

Formation of the seasonal thermocline in spring and summer and its disappearance in fall and winter represent one of the best examples of the connection between physical, chemical, and biological processes in the ocean. The seasonal dynamics of food webs—from tropical to polar ocean—emerge from the seasonal cycle of heating and cooling. In turn, these dynamics drive changes in the chemistry of the upper ocean, which have important implications for the carbon cycle and Earth’s climate. More will be revealed in the chapters ahead.

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