Double diffusive convection (DDC) plays a role in small scale mixing in the oceans, which ultimately act as a critical driver for large, even global scale processes. DDC plays a significant role in upwelling of nutrients and vertical transport of heat and salt in oceans. Salt fingering contributes to vertical mixing in the ocean, which helps to regulate the gradual circulation of the ocean, which in turn controls the climate of the earth. It also helps to understand the temperature-salinity patterns in oceans (Thermohaline staircase) as shown in figure.
Figure: Temperature and salinity profile in the West Atlantic (Thermohaline staircase).
source: https://gfd.whoi.edu/wp-content/uploads/sites/18/2018/03/lecture10_136325.pdf
