Climate change: what is happening in the ocean?

Climate change: what is happening in the ocean?

There is continued scientific and public debate about the possibility of future climatic changes that may result from human activity such as the burning of fossil fuels since the 18th century. Within this context, the article provides a brief review of the ocean's role within the global climate system. It illustrates how the ocean regulates the Earth's climate and how it asserts control over the climate system. One key feature of the present state of the ocean climate is a global thermohaline circulation, which allows for an exchange of heat and greenhouse gases in a conveyor belt type fashion throughout the ocean interior. Continuous mixing of surface water into the deep ocean caused by complex ocean and atmosphere processes may have already led to a global ocean warming. The detection of a human induced greenhouse effect against the background of natural climate variability is a difficult task. Daily, seasonal, or decadal changes in temperature, for example, are much larger than the anticipated human induced temperature increase of only several tenths of a degree. This climate variability is discussed by using several prominent examples. In the last section of this article, observations of climate variability in the South Pacific Ocean are described. It is here, where a fingerprint of global ocean warming may have already been found in recently collected data. When compared to historical data records from the 1960s, these new data indicate a warming of the subsurface ocean. Today's policy and decision makers wait for more pronounced signals of an enhanced greenhouse effect to arrive and scientists continue to search for further convincing evidence. However, one benefit of global climate and ocean research is the discovery and study of a suite of previously unknown climate system phenomena during the last two decades.