Abstract:
The Northern Mozambique Channel has been an area of interest for several marine
operations in the prospecting and exploiting of offshore hydrocarbons. Thus, a detailed
understanding of the local circulation and dynamics is crucial for safety and environmental
monitoring in case of an oil spill event. In the present study, a combination of different data
set products was used to infer the structure of the currents and the related processes that
affect their variability in the Northern Mozambique Channel. We used CTD and ADCP
measurements data collected during the research cruise ship “Dr Fridtjof Nansen” in March
2018, and the satellite altimetry-derived geostrophic currents. A longitudinal transect was
considered off Cabo-Delgado, Quissanga district - 12 o S with almost 100 km distance, we
concentrated on the upper 200 m depth where we have ADCP measurements. Our results
presented three different modes of the current structure from a horizontal perspective: on the
coastal tip, the currents are southwards orientated with moderate velocities of up to 0.6 m/s
and vertically homogeneous, intensifying towards the sea at 1000 m isobaths with strong
velocities of up to 1 m/s south-westwards orientated, while on the eastern part of the transect
at around 2000 m isobaths, the near-surface currents (above 50 m depth) are completely
weak (< 0.2 m/s) and are north-westwards orientated. The weak north-westwards currents at
the near-surface (above 50 m depth) observed off 2000 m isobaths are wind-driven, with less
influence from the Sea Surface Height gradient. The strong south-westerly currents are found
to be a result of the Sea Surface Height gradient, and their intensity is affected by the rugged
steering topography on the west coast of the Channel. Moreover, the Channel is dominated
by anticyclonic eddies propagating southwards with current speeds (> 1 m/s). These results
suggest the need for delicate and suitable materials and methods for offshore operations, as
the floating platform installations will have to withstand very strong currents up to a depth
of more than 1000 m. The current speeds are fast enough to move the spilt oil to the coast
quickly, affecting the coastal ecosystems and consequently human health.
