Thermohaline Circulation

Assembled from 17 blocks · 2 evidence · 46 related

1. Story
2. The part of ocean circulation driven by density rather than by wind. Seawater density rises as it cools and as salt is concentrated in it — by evaporation, or by sea ice forming and rejecting brine — and where surface water becomes denser than the water beneath it, it sinks. That happens in only a few small places: the Labrador and Nordic seas in the north, and a handful of shelf regions around Antarctica in the south. The sunk water spreads at depth, mixes slowly, and returns to the surface diffusely over the rest of the world ocean, so the circuit is grossly asymmetric — sinking is concentrated and rising is spread out. Radiocarbon ages give a sense of the timescale: deep water in the North Pacific is roughly two thousand years older than deep water in the North Atlantic. Wallace Broecker's 1987 "great ocean conveyor" cartoon made the idea famous and, by simplifying it into a single looping belt, also made it easy to misunderstand.
3. Knowledge
4. Thermohaline Circulation
5. Connections
6. Atlantic Meridional Overturning Circulation (AMOC)
7. Coastal and Equatorial Upwelling
8. Antarctic Bottom Water (AABW)
9. Southern Ocean
10. Argo Profiling Float Array
11. Wallace Broecker
12. The great ocean conveyor is drawn
13. The Argo design array is completed
14. IPCC AR6 assesses AMOC decline as very likely and collapse as unlikely this century
15. Evidence
16. The article in which the "great ocean conveyor" diagram of global thermohaline circulation first appeared, drawn as a cartoon for a lay readership in a discussion of the Younger Dryas. Citation details taken from a Journal of Physical Oceanography review of the conveyor concept read via search summary; the original article was not consulted.
17. Radiocarbon ages differ by about 1,000 years between the North Atlantic and the Southern Ocean and by a further 1,000 years between the Southern Ocean and the North Pacific, making deep North Pacific water the oldest in the ocean. Read via search summary alongside reporting of a 2017 study on the North Pacific "shadow zone"; neither paper was fetched.