第九届青年地学论坛

Using Surface Drifters and Argo profiles, wind-driven near-inertial dissipation and associated mixing in the surface mixed layer (SML) are estimated, with the globally averaged dissipation rate of 4.3×10^-8 m²/s³ and diapycnal diffusivity of 5.1×10^-5 m²/s at the SML base. On this basis, this paper demonstrates that SML nitrates supplied by near-inertial mixing (NIM) can effectively contribute to elevation of surface chlorophyll-a concentrations in the Southern Ocean. Quantitative analysis from the SML nitrate mass balance equation shows that entrainment/detrainment controls seasonal variations of the SML nitrate budget but the annual nitrate change (-17.8 mmol/m²•year) is mainly caused by NIM-driven nitrate diffusion (525.6 mmol/m²•year) and biological drawdown (-507.8 mmol/m²•year), with a minor role from entrainment/detrainment (-56.9 mmol/m²•year). Spatial variation of the year-mean chlorophyll-a concentration mainly follows that of NIM-induced annual nitrate flux, suggesting a key role of NIM in vertical nitrate transport available for elevating primary production in the Southern Ocean.
 

Near-inertial Mixing,nitrate,primary productivity