Editing Agulhas Current (section)

===Agulhas Undercurrent===
Directly under the core of the Agulhas Current, at a depth of {{Convert|800|m|abbr=on}}, there is an Agulhas Undercurrent which flows equatorward.<ref>{{Harvnb|RSMAS|2005}}</ref>  The undercurrent is {{Convert|2000|m|abbr=on}} deep and {{Convert|40|km|abbr=on}} wide and can reach {{Convert|90|cm/s|abbr=on}} at {{Convert|1400|m}}, one of greatest speeds observed in any current at this depth, but it also displays a great variance with a transport of 4.2±5.2 Sv.  The undercurrent can represent as much as 40% of the Indian Ocean [[meridional overturning circulation|overturning transport]].<ref name="Beal-2009-Intro">{{Harvnb|Beal|2009|loc=Abstract, Introduction, pp. 2436-2437}}</ref>

Below {{Convert|1800|m|abbr=on}} a separate layer of the undercurrent can be distinguished: the more coherent [[North Atlantic Deep Water]] (NADW) which transports an average of 2.3±3.0 Sv.<ref name="Beal-2009-Intro" />  NADW rounds the southern tip of Africa after which the major part (9 Sv) flow eastward and a smaller part (2 Sv) northward through the Agulhas Undercurrent and into the [[Natal Valley]] (the basin between South Africa and the Mocambique Plateau); remnants of NADW has been observed in the [[Mozambique Basin]] and [[Mozambique Channel|Channel]].  The undercurrent is more leaky than the Agulhas above, resulting in a relatively well-mixed composition of water masses&nbsp;&mdash; at intermediate depth there is a mixture of [[Antarctic Intermediate Water]] and [[Read Sea Water]].<ref name="Beal-2009-Disc">{{Harvnb|Beal|2009|loc=Discussion and summary, pp. 2448-2449}}</ref>

The periodicity of the meanders and Natal pulses of the Agulhas is matched by the Agulhas Undercurrent.<ref name="Beal-2009-Intro" />  More research is needed but observations seem to indicate that during a meander event the Agulhas moves first onshore, then offshore, and finally onshore again, first weakening then strengthening 10-15 Sv.  At the same time the undercurrent is first squeezed offshore and weakened when the Agulhas moves onshore, then strengthened and forced upward when the Agulhas moves offshore, and finally returns to normal.<ref name="Beal-2009-Disc" />