TRANSPORT AND MIXING AT THE
SOUTHWEST INDIAN RIDGE
The Indian Ocean harbours an important but poorly understood part of the global meridional ocean overturning circulation, which transports heat to high latitudes. Understanding heat exchange in the Indian Ocean requires knowledge of the magnitudes and locations of both meridional deep-water transport and mixing, but in particular the latter is poorly constrained at present.
We made detailed measurements of transport and mixing in the narrow Atlantis II fracture zone in the Southwest Indian Ridge, one of the main conduits for equatorward-flowing deep water. We observed a northward jet of deep and bottom water extending 1,000 m vertically with a transport of 3 Sv. The flow was contained below the sides of the fracture zone (black and grey lines in the figure below).
Turbulent diffusivity within the jet was up to two orders of magnitude above typical deep ocean levels in our measurements. The flow through this narrow fracture zone is about 25% of the total meridional overturning circulation in the Indian Ocean. The elevated turbulence in this deep sheared flow is not hydraulically controlled, in contrast to many other fracture zones.
This research was funded by the National Science Foundation and the University of California Ship Funds.