Ocean and Climate
The ocean and atmosphere are partners in creating our climate. By circulating heat and water around the planet and transferring it to the atmosphere, the ocean plays a critical role in Earth’s climate system. A large portion of this heat transport occurs in the North Atlantic Ocean. Scientists do not fully understand how climate changes in the tropical Pacific and Atlantic Oceans are linked to changes in the North Atlantic and Arctic Oceans. But the Atlantic clearly amplifies and extends climate changes, with significant impacts in Europe and the U.S. East Coast.
The northern North Atlantic is one of the few places on Earth where relatively cold, salty waters are dense enough to sink to the abyss. The plunge of this great mass of cold, salty water propels a system of global ocean circulation called the Ocean Conveyor. The Conveyor also draws warm, salty tropical waters northward into the North Atlantic. This pumps heat into the region (which significantly raises average winter temperatures), as well as salt (which makes North Atlantic waters denser and increases sinking that drives the Conveyor). Changes in this strategic region can lead to widespread and potential abrupt climate changes.
Observations and measurements in the ocean, especially the Arctic and Atlantic, are critical to understand the ocean’s role in climate. Using the latest technology—from the long core and ocean observatories to autonomous underwater vehicles—WHOI scientists are working to answer some of science’s most challenging questions about the planet’s future climate.
Schematic of the hydrologic (water) cycle near the coast. (Illustration by Jack Cook, Woods Hole Oceanographic Institution)
The Hydrological Cycle
With 86 percent of global evaporation and 78 percent of global precipitation occurring over the oceans, the role of the ocean water cycle in the global climate system has received increasing attention. Changes in the ocean water cycle have far-reaching effects on global climate, as they not only drive the changes of ocean circulation but also exacerbate the severity of the terrestrial hydrologic events. There is ever-increasing evidence that the origins of flood and drought cycles on land are closely linked to variations of the ocean water cycle. The close connection between the oceanic and terrestrial water cycles leads to key questions in the global climate debate: if the ocean keeps warming up, how will the ocean water cycle change and what will be the consequences of such change on society’s water needs that are land-based. Understanding these questions is important because water is at the heart of both the effects and causes of the global climate change.
Carbon and the Ocean
The ocean and atmosphere are linked in an important chemical relationship, as the ocean is both a source and sink of atmospheric carbon dioxide (CO2). Of the greenhouse gases, carbon dioxide is perhaps the most important because of its strong links to human activities. Since the start of the Industrial Revolution, atmospheric carbon dioxide has risen steadily, contributing to an average increase in global temperatures of about 0.8°C.
The ocean is a major sink for atmospheric CO2 through many physical and biological processes that result in chemical exchanges between the ocean and the atmosphere, and between the upper ocean and the deep ocean. Over time, organic carbon settles into the deep ocean, ultimately stored in deep sea sediments—a process referred to as the “biological pump” – a natural process for removing excess CO2 from the atmosphere. An important consequence of the current, rapid increase in CO2 of the upper ocean is that the surface waters are becoming more acid as the CO2 is transformed into carbonic acid through chemical reactions in the water. These chemical changes have the potential to disrupt some important ecosystems that rely on the production of shell material made of calcium carbonate (including many organisms of commercial value).
The warming of the ocean may also reduce the future rate of uptake of CO2 from the atmosphere because warmer water holds less CO2 than colder waters. Changes in the ocean circulation may also reduce the ability of the ocean to take up the world’s carbon and reduced uptake of CO2 by the oceans means that more will stay in the atmosphere and increase the rate of warming. Today we don’t really understand the interactions of the ocean, atmosphere, and the biosphere well enough to know how much CO2 will continue to be absorbed by the oceans and how much will remain the atmosphere in the future.
Last updated: July 1, 2015