The Southern Ocean (SO) is the worlds largest high nutrient low
chlorophyll region, and has a plentiful supply of underutilised
macronutrients due to light and iron limitation. These macronutrients
supply the rest of the neighboring ocean basins, and are hugely
important for global productivity and ocean carbon sequestration.
Vertical mixing rates in the SO are known to vary by an order of
magnitude temporally and spatially, however there is great uncertainty
in the parameterization of this mixing, including in the specification
of a background value in coarse resolutation Earth System Models. Using
a biogeochemical-ocean model we show that SO biomass is highly sensitive
to altering the background diapycnal mixing over short timescales.
Increasing mixing enhances biomass by altering key biogeochemical and
physical parameters. An increased surface supply of iron is responsible
for biomass increases in most areas, demonstrating the importance of
year round diapycnal fluxes of iron to SO surface waters. These changes
to SO biomass could potentially alter atmospheric CO2 concentration over
longer timescales, alluding to the importance of accurate representation
diapycnal mixing in climate models.