Morphology of the seafloor in the Southern Mozambique Channel: Evidence for long-term persistent bottom-current flow and deep-reaching eddy activity

• Main Authors: Breitzke, Monika, Wiles, Errol, Krocker, Ralf, Watkeys, Michael Keith, Jokat, Wilfried
• Format: Conference Object
• Language: unknown
• Published: AGU 2012
• Subjects: Antarc*; Antarctic
• Online Access: https://epic.awi.de/id/eprint/30507/; https://hdl.handle.net/10013/epic.39799

New high-resolution bathymetric and sub-bottom profiler data collected in the Southern Mozambique Channel along a grid of 16 parallel, non-overlapping lines show a large variety of bedforms which were formed by strong bottom currents. They are visually classified into four main microtopographic zones and several sub-zones which divide the study area into regions with (1) smooth seafloor, (2) undulating bedforms, (3) seamounts and islands, and (4) the Zambezi Channel. A smooth seafloor occurs on the Mozambican continental slope together with downslope mass-wasting processes, north and south of Bassas da India, on the eastern levee of the Zambezi Channel and in the Zambezi cone. Undulating bedforms of some kilometres wavelength and several tens of metres height cover most of the southern, central and northeastern study area. The most spectacular bedforms are numerous, closely spaced, giant erosional scours of up to ~450 m depth, more than ~20 km length and ~3 - 7 km width in the southwestern part of the study area. Here, northward flowing Antarctic Bottom Water (AABW) is topographically blocked to the north and deflected towards the east due to the shallowing bathymetry of the Mozambique Channel. SW-NE trending undulating bedforms aligned parallel to the deflected AABW and interpreted as small contourite mounds allow to trace the AABW flow path eastwards. An ~100 km long W-E trending channel indicates the northernmost extension of the AABW. NW-SE oriented undulating bedforms in the west, hummocky bedforms in the east and arcuate, cross-cutting features in-between reflect a completely different current regime in the central study area. Comparisons with LADCP sections show, that the western part lies in the range of deep-reaching anticyclonic Mozambique Channel eddies (MCEs), so that the undulating bedforms are again considered to be small contourite mounds aligned parallel to a part of the swirl. The cross-cutting features in the middle mark the eastern boundary of the MCE, where a northbound flow direction ...