A meltwater induced collapse of the ’conveyor belt’ thermohaline circulation and its influence on the distribution of Δ14C and δ180 in the oceans

• Main Author: Mikolajewicz, U.
• Format: Report
• Language: English
• Published: 1996
• Subjects: North Atlantic
• Online Access: http://hdl.handle.net/21.11116/0000-0003-25DE-A; http://hdl.handle.net/21.11116/0000-0003-25E0-6

An ocean general circulation model coupled to a nonlinear energy balance model of the atmosphere and a statistical feedback model for wind stress shows a temporary collapse of the ’conveyor belt’-type thermohaline circulation in response to a prescribed meltwater input of 500 years duration. The thermohaline circulation of the Atlantic reverses. The associated changes in ocean heat transport lead to a strong cooling in the North. Atlantic and in Europe. Due to the windstress feedback, the mode without North Atlantic deepwater formation is slightly unstable and the system slowly returns to the ’conveyor belt’ overturning mode. The circulation changes leave a strong imprint in geochemical tracers included in the model simulations. Radiocarbon chronologies are strongly affected, showing a rapidly advancing radiocarbon ’clock’ when formation of North Atlantic deepwater collapses and a very slowly moving radiocarbon ’clock’ when the conveyor-belt overturning starts again. In the deep Atlantic, the changes in the origin of the water masses lead to a rapid increase of the differences in radiocarbon ages relative to the surface waters. 6180 shows a similar time evolution as salinity, but the errors in the reconstruction of salinity from 6180 are typically larger than 1 psu during meltwater input. Much of the meltwater signal in sea water is obscured in carbonate shells due to the temperature effect.