Chapter 3 Key Concepts

Climate change has caused the ocean to increase in temperature, sea and land ice to retreat, and the oceans to acidify to alarming degrees.
This chapter discusses the form of climate change in terms of oscillations and longer-term trends, then the main atmospheric drivers of global climate change, and finally, a crucial side-product of increases of carbon dioxide: acidification of the ocean.
Oscillations and directional change in climate occur at large oceanic spatial scales. They interact to result in climate variability.
Multidecadal oscillations in climate are a major pattern observed throughout the world’s oceans. World climate patterns in recent decades are usually a combination of oscillations combined with a long-term warming trend.
Climate oscillations are irregular alternations between coupled atmosphere−oceanic states that result in changes of wind systems, oceanic currents, and regional climate.
El Niño is a global-scale climate oscillation dominated by a major warming event that spreads from west to east in the tropical Pacific Ocean.
In the Atlantic, the North Atlantic Oscillation causes strong fluctuations in wind systems and oceanic climate.
The Arctic Oscillation Index causes major alternations of climate in the North Atlantic. Its timing is strongly correlated with the North Atlantic Oscillation Index.
The Pacific Decadal Oscillation causes decadal switches in climate, may strongly affect coastal marine food webs, and facilitates large movements of mobile large predators north or south along the Pacific coast of North America.
Earth and oceanic climate are moderated because of the greenhouse effect.
Atmospheric quantities of carbon dioxide have increased strongly because of the burning of fossil fuels and less so owing to deforestation; these factors are warming the earth’s surface and ocean waters.
Seawater temperatures have been increasing over the past century.
Increased temperature has caused sea-level rise and major changes in oceanic circulation, sea-ice coverage, and water column structure.
Increased temperature may cause increases of ocean stratification, reduction of dissolved oxygen, and intensification of midwater oxygen minimum layers.
Increased temperature may cause physiological stress on marine populations, reorganizations of food webs, and changes in geographic ranges of species.
Carbon dioxide additions to the atmosphere result in increased dissolved CO₂, decreased pH, and increased problems for some calcifying organisms in the sea.
Ocean acidification is being accelerated in certain environments such as eastern Pacific upwelling centers where dissolved oxygen is low and waters rise toward shore environments, but also in coastal environments where human-influenced degraded coastal waters result in lower dissolved oxygen.