The U.S. contribution to a large international effort to document long-term trends in carbon storage and transport in the global oceans by reoccupying selected hydrographic sections on decadal timescales began with three North Atlantic cruises in 2003. The initial results from these reoccupation cruises have shown significant long-term changes in oxygen, carbon dioxide (CO2), and several other measurable parameters since the last global survey, which occurred in 1993.
The ocean has a memory of the climate system and is second only to the Sun in affecting variability in the seasons and longterm climate change. The ocean stores an estimated 1000 times more heat than the atmosphere, and 50 times more carbon. Additionally the key to possible abrupt climate change may lie in deep-ocean circulation.