_:b1218156 . _:b1218156 . _:b1218156 . _:b1218156 "A marine downwelling describes a net current of marine surface water towards deeper regions of the water column. Marine downwellings are usually caused by differences in the density (and hence, temperature and salinity) of seawater."^^ . _:b1218156 "PLB:plb"^^ .