Climate Change Science - Increasing Temperature of the Ocean

Australia: The Land Where Time Began

Climate Change Science - Increasing Temperature of the Ocean

The World Ocean is the greatest reservoir of heat on Earth, responding to changes in temperature more slowly that either the atmosphere or land. Warming resulting from human activities that emit carbon dioxide has caused the average global atmospheric temperature to increase by about 1^oF over the past century. The temperature increase in the oceans over this period has been 0.18^oF. This warming has reached to a depth of about 700 m (2,300 ft), which is the zone in which most marine life inhabits.

The ocean is an important part of the variability of the climate and climate change. The heat capacity of the ocean is about 1,000 times greater than that of the atmosphere, and since 1960 the net uptake of heat by the ocean is about 20 times higher than that of the atmosphere. This large amount of heat, that is stored mainly in the upper layers of the ocean, has a crucial role in climate change, variations on decadal and seasonal time scales in particular. The level of the ocean rises when its temperature rises because of thermal expansion and if the heat of the ocean waters continues rising there will be severe consequences for the food chain of the world.

Sea-Surface Temperatures (SSTs) – relative distribution

Climate and weather patterns around the Earth are greatly influenced by sea surface temperatures. A wide swathe of water in the Pacific Ocean along the Equator that warms by 2-3^oC every 3-7 years is an example. The El Niño causes this warming, which is a hallmark of this weather pattern, changing rainfall patterns around the world, with heavy in the southeastern US and severe drought in Australia, Indonesia and southern Asia. Tropical cyclones (typhoons and Hurricanes) on a smaller scale draw energy from warm ocean waters to form and intensify. It has been found that there is a direct relationship between the strength of the El Niño on the number of storms and their intensities.

In a time series, which can be downloaded at no cost from http://earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MYD28M, the most obvious patterns shown is the year-round difference in temperature of the sea surface between the poles and the equatorial regions. It can be seen that various warm and cool currents stand out, even when the monthly averages of sea surface temperature. The Gulf Stream, a band of warm waters, flows north along the east coast of the US and then to the east across the North Atlantic Ocean.

A few events show up, though short-lived weather events that have an influence on the temperature of the ocean are often hidden in monthly averages. An example occurred in December 2003, when strong winds blew to the southwest from the Gulf of Mexico across Central America towards the Pacific Ocean, which drove warm surface waters away from the coast, which allowed cold water to upwell to the surface. These winds, the Tehuano winds, are a recurring phenomenon.

Heat content of the ocean

It has been found that about 93.4 % of the heat that has built up by the Earth has been taken up by the World Ocean. The ocean is thought of by climate scientists and oceanographers as having a “skin” comprised of the upper layer of from a few millimetres to a few metres. This sunlight warms this “skin” and the accumulating heat begins to move downwards into the deeper in the ocean. As stated by the 2^nd law of thermodynamics, as heat continues to accumulate in the surface layer of the ocean, if the atmosphere is cooler heat begins to move into the atmosphere, and down into the deeper parts of the ocean which is also cooler, and is dispersed in all directions by the ocean currents.

It has been documented that glacial ice on the west coast of Antarctica is being melted by warmer waters in the Southern Ocean. The ice of the West Antarctic ice shelves is being melted by the warming waters of the Southern Ocean. These ice shelves have been slowing the progress of glaciers on land into the sea, therefore as the ice shelves melt more ice from the land is moving into the sea to replace them, thereby leading to sea level rise.

A graph of the rise of heat in the World Ocean can be seen on

http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/ ; public domain.

Sources & Further reading