The Ocean’s effect on seasons

One of the most obvious demonstrations of water's ability to diminish temperature changes can be seen in the ocean and its effect on weather and climate.

The summer solstice (usually June 21^st) is the day when the Northern hemisphere receives the most sunlight. If there were no other influences on temperature, this should be our hottest day of the year, yet the hottest day on the Eastern seaboard of the United States generally occurs more than a month after that time, in late July or early August.

By the same token, the Northern hemisphere receives the least energy from the sun on the winter solstice (usually December 21^st) but the Eastern seaboard often doesn’t see snow until January and the coldest day often falls as late as February.

It is important to note, however that the same can not be said for all places on Earth or even all places in North America.

It is not uncommon for the middle of the USA to experience heat waves in May and snow in November. In simplest terms, the seasons lag behind the sun but do so much more dramatically on the coasts than they do in the middle of the country.

The reason for this is simple. The ocean is a huge heat sink and is in contact with both the atmosphere and the land mass that makes up our continent. As such, it has a moderating effect on the temperature experienced.

Let’s say all of that again, but this time in English.

Seasons - a more complete explanation

As the winter comes to an end and the days begin to get longer, both the ocean and the land are cold (although the ocean is not as cold as the land). Sunlight is absorbed by both the ocean and the land and they begin to get warmer, and to warm the air above them. However the heat capacity of the ocean is huge compared to that of the land, thus the land warms up more quickly than the ocean does. Likewise, the air over the land warms more than the air over the ocean.

Since the land and ocean are in contact, heat can transfer between them. Thus the warm land gives heat to the cold ocean and is cooled down in the process. The air above the ocean and land are also constantly mixed by wind and weather patterns, preventing one from being significantly hotter than the other.

Through all of the spring, energy is absorbed by both land and water and their temperatures increase slowly, the land held back by its contact with the colder ocean. As late June and the longest day of the year arrive, the ocean is still relatively cold and is, therefore, still taking heat from the land, preventing it from becoming too hot.

As summer continues, the ocean, having absorbed heat from both the sun and the land for many months continues to get slowly warmer. As the temperature of the ocean gets closer to that of the land, it begins to take less heat from the land, allowing the land to get warmer. Thus, by August, more of the energy absorbed by the land stays with the land and the temperature rises. The land continues to feed heat to the ocean throughout the summer, albeit at a slower pace, which is why the ocean is at it’s warmest in early September.

As summer ends and the fall begins, less and less energy is available from the sun. As a result the temperature of both land and ocean start to fall. However, the ocean is such a huge heat sink that its temperature drops much more slowly.

Within a month or two, the ocean is warmer than the land the transfer of heat changes direction. Thus, the warm ocean prevents the land from becoming too cold. By late December, the ocean is still warm enough to prevent the land from becoming too cold and the air from producing snow.

As winter continues, and the ocean continues to give away heat its temperature drops more and more. As the temperature difference between the ocean and the land becomes smaller, the rate of heat transfer slows and the land cools more quickly.