Precipitation over the region of southern Africa is largely influenced by remote and adjacent ocean conditions (Pomposi et al., 2018), through various mechanisms. In today’s post, we look into the impact that the Agulhas Current (AC) exhibits on precipitation along the eastern coast of South Africa (SA).
The AC is the strongest western boundary current (WBC) in the southern hemisphere (Njouodo et al., 2018). As a WBC, it is responsible for transferring large amounts of warm and saline water from the Indian Ocean to the eastern coast of SA (it is estimated that it transports ~70 Sverdrup (Sv, 1Sv=10^6 m^3 s^-1)) (Njouodo et al., 2018).
The impact that the AC exerts on different scales is a very interesting topic of concern, especially for oceanographers, however, large knowledge gaps still exist. On a local-regional scale, the AC has been associated with a co-located band of precipitation along the eastern coast of SA. The AC is typically characterized by steep SST and SLP gradients and convergence of low-level winds that favor convection (Njouodo et al., 2018).
Apart from its local impact, the AC through the Agulhas Leakage (AL), affects the Atlantic Meridional Overturning Circulation (AMOC), feeding it with warm and saline water (Beal et al., 2011). Climate change is expected to cause an increase to the AL, bringing more salty and warm water from the Indian Ocean to the Atlantic Ocean (Beal et al., 2011). The increase of the AL is largely caused by the southward migration of the Indian Ocean subtropical gyre (Yang et al., 2020).
Speed of sea currents at 6/1/2021. Map taken from Windy.
Sea surface temperature at 6/1/2021. Map taken from Windy.
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