Changes in ocean water mass properties: oscillations or trends?
Harry L Bryden1, Elaine L McDonagh, Brian A King
1Southampton Oceanography Centre, Empress Dock, Southampton SO14 3ZH, UK. h.bryden@soc.soton.ac.uk
Science (New York, N.Y.)
|June 28, 2003
Summary
Thermocline mode waters have recently become saltier and colder, reversing a trend of freshening observed from 1965 to 1987. These findings reveal significant natural oscillations in oceanographic properties.
Area of Science:
- Oceanography
- Climate Science
Background:
- Thermocline mode waters are crucial indicators of oceanographic changes.
- Previous interpretations linked freshening trends to anthropogenic climate change.
Purpose of the Study:
- To analyze long-term changes in thermocline mode water properties.
- To compare hydrographic data from multiple decades.
Main Methods:
- Utilized five hydrographic sections spanning from 1936 to 2002.
- Analyzed temperature and salinity data for upper thermocline waters (10-17°C).
Main Results:
- Mode waters showed little change between 1936 and 1965.
- Observed freshening from 1965 to 1987.
- Since 1987, mode waters have become significantly saltier and colder.
Conclusions:
- Recent changes in mode waters largely reverse the 1965-1987 freshening trend.
- Substantial natural oscillations, not solely anthropogenic factors, influence mode-water properties.
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