Antarctic Polar Front (Antarctic Convergence)

Assembled from 18 blocks · 1 evidence · 50 related

1. Story
2. The circumpolar boundary where cold Antarctic surface water flowing north meets and sinks beneath warmer sub-Antarctic water. It is a sharp front, often crossed in a matter of hours by ship, with a surface temperature step of several degrees. It functions as a biological wall as much as a physical one: the species assemblage on either side differs profoundly, and Antarctic krill is essentially confined to the cold side of it. Its position wanders with longitude and season, running roughly between 50 and 60 degrees south, and it is the reason the Southern Ocean can be defined biologically rather than by an arbitrary line of latitude. It is also a large part of the answer to why nothing walked back into Antarctica: the isolation is oceanographic before it is geographic.
3. Knowledge
4. Antarctic Polar Front (Antarctic Convergence)
5. Antarctic Circumpolar Current (ACC)
6. Connections
7. Antarctic Circumpolar Current (ACC)
8. Antarctic Krill (Euphausia superba)
9. Antarctica
10. Antarctic Polar Front (Antarctic Convergence)
11. Atlantic Meridional Overturning Circulation (AMOC)
12. Drake Passage
13. Southern Ocean
14. Drake Passage
15. A circumpolar current becomes possible
16. Drake Passage is measured and the ACC turns out to be larger
17. Evidence
18. Analysis of a compiled database of scientific net hauls indicates a long-term decline in Antarctic krill density in the southwest Atlantic sector, correlated with reduced winter sea-ice extent, together with an increase in salp abundance. V55 VERIFICATION BASIS: not opened during production; no research channel was available. The magnitude of the reported decline is deliberately not quoted anywhere in this pack, because subsequent work has contested it and the figure could not be checked.