Heat retention in continents and oceans

Continents (land) and oceans (bodies of water) respond very differently to heat from the sun. In the height of summer, we cannot walk barefoot on cement, and yet we can cool off in a pool. At night, the cement cools off rapidly; then, the pool seems warm. Because fluids are mobile, heat can be more easily distributed through a larger area in fluids than in solids. While solids quickly become hot to the touch, just a short distance below the surface, temperatures remain cool (a property that keeps cellars cool in the summer). Heat is distributed more evenly through a liquid than through a solid; thus the entire liquid needs to be cooled in order for the liquid to feel cool to the touch. In the case of a solid, the exterior can be cool while the interior remains hot; we need cool only the exterior, not the entire solid. Ultimately, this means that oceans are slower to warm and slower to cool than continents.

Consider how these properties of continents and oceans might modify climates. At the dawn of the Mesozoic, the continents were united into the single land mass, Pangaea (see Figure 2.5). Here, continental effects - more rapid warming and cooling of continents than oceans - would have been more intense than today. Pangaea must have experienced wide temperature extremes. It would have heated up quickly and become hotter, and then cooled off rapidly, and become colder, than do modern continents, whose continental effects are mitigated by the broad, temperature-stabilizing expanses of oceans between them.

The post-Late Triassic break-up of Pangaea mitigated the strong continental effects (see Figures 2.6 and 2.7). With the rise in eustatic sea level and supercontinental dismemberment, the effects of the large epeiric seas were superimposed upon the diminishing continental effects. For example, the strong continentality (hot, dry summers; cold winters) observable even today in the interiors of continents would have been decreased by the presence in the Jurassic and Cretaceous of the large continental seaways. These large bodies of water would have stabilized global temperatures, decreasing the magnitude and rapidity of the temperature fluctuations experienced on the continents during times of lower sea level.

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