Approximately 71% of the Earth’s surface is covered by water. Moreover, well over 99% of the total heat budget of the earth is contained in the ocean. We have already seen how heat is the engine behind climate dynamics. It logically follows, therefore, that the oceans are an integral part of climate. In this section, we will focus on the physics of ocean circulation and how it helps drive climate. We will show that the effect on climate can be very large (including the whole ocean) or more regional, limited to an individual storm system. Finally, we will focus on ways in which the ocean is likely to change in the future and how that change will have a profound impact on climate.
If you have spent time at the beach or in a coastal city, you will likely appreciate the way in which the ocean affects the weather and climate of the coastal region. Oceans have a tremendously high heat capacity, so they have a large damping effect on climate. In the summer, the ocean acts to cool the land, and in the winter the opposite effect occurs and the land is kept warmer. Take coastal California, for example. In the months of June and July, San Francisco is one of the coldest locations in the United States, yet in the winter, the city is among the warmest places. This dichotomy is a result of the effect of heat from the Pacific Ocean influencing the climate of the California coastline.