Joubert, WRSwart, STagliabue, AThomalla, Sandy JMonteiro, Pedro MS2014-07-182014-07-182014-03Joubert, W.R., Swart, S., Tagliabue, A, Thomalla, S.J. and Monteiro, P.M.S. 2014. The sensitivity of primary productivity to intra-seasonal mixed layer variability in the sub-Antarctic Zone of the Atlantic Ocean. Biogeosciences Discuss, vol. 11, pp 4335- 43581810-6277http://www.biogeosciences-discuss.net/11/4335/2014/bgd-11-4335-2014.pdfhttp://hdl.handle.net/10204/7491Copyright: 2014 European Geosciences Union (EGU). This is an Open Access journal. The journal authorizes the publication of the information herewith contained. Published in Biogeosciences Discuss, vol. 11, pp 4335-4358The seasonal cycle of primary productivity is impacted by seasonal and intra-seasonal dynamics of the mixed layer through the changing balance between mixing and buoyancy forcing, which regulates nutrient supply and light availability. Of particular recent interest is the role of synoptic scale events in supplying nutrients, particularly iron, to the euphotic zone in the Sub Antarctic Zone (SAZ), where phytoplankton blooms occur throughout summer. In this study, we present high resolution measurements of net community production (NCP) constrained by ÉO2/Ar ratios, and mixed layer depth (MLD) in the Atlantic SAZ. We found a non-linear relationship between NCP and MLD, with the highest and most variable NCP observed in shallow MLDs (< 45m). We propose that NCP variability in the SAZ may be driven by alternating states of synoptic scale deepening of the mixed layer, leading to the entrainment of iron (dFe), followed by restratification, allowing rapid growth in an iron replete, high light environment. Synoptic iron fluxes into the euphotic zone based on water column dFe profiles and high resolution glider MLD data, reveal a potentially significant contribution of “new iron” which could sustain NCP throughout summer. Future process studies will help elaborate these findings further.enOceanographyIntra-seasonal dynamicsClimate researchSynoptic scalesSub Antarctic ZoneSAZÉO2/Ar ratiosArticleJoubert, W., Swart, S., Tagliabue, A., Thomalla, S. J., & Monteiro, P. M. (2014). The sensitivity of primary productivity to intra-seasonal mixed layer variability in the sub-Antarctic Zone of the Atlantic Ocean. http://hdl.handle.net/10204/7491Joubert, WR, S Swart, A Tagliabue, Sandy J Thomalla, and Pedro MS Monteiro "The sensitivity of primary productivity to intra-seasonal mixed layer variability in the sub-Antarctic Zone of the Atlantic Ocean." (2014) http://hdl.handle.net/10204/7491Joubert W, Swart S, Tagliabue A, Thomalla SJ, Monteiro PM. The sensitivity of primary productivity to intra-seasonal mixed layer variability in the sub-Antarctic Zone of the Atlantic Ocean. 2014; http://hdl.handle.net/10204/7491.TY - Article AU - Joubert, WR AU - Swart, S AU - Tagliabue, A AU - Thomalla, Sandy J AU - Monteiro, Pedro MS AB - The seasonal cycle of primary productivity is impacted by seasonal and intra-seasonal dynamics of the mixed layer through the changing balance between mixing and buoyancy forcing, which regulates nutrient supply and light availability. Of particular recent interest is the role of synoptic scale events in supplying nutrients, particularly iron, to the euphotic zone in the Sub Antarctic Zone (SAZ), where phytoplankton blooms occur throughout summer. In this study, we present high resolution measurements of net community production (NCP) constrained by ÉO2/Ar ratios, and mixed layer depth (MLD) in the Atlantic SAZ. We found a non-linear relationship between NCP and MLD, with the highest and most variable NCP observed in shallow MLDs (< 45m). We propose that NCP variability in the SAZ may be driven by alternating states of synoptic scale deepening of the mixed layer, leading to the entrainment of iron (dFe), followed by restratification, allowing rapid growth in an iron replete, high light environment. Synoptic iron fluxes into the euphotic zone based on water column dFe profiles and high resolution glider MLD data, reveal a potentially significant contribution of “new iron” which could sustain NCP throughout summer. Future process studies will help elaborate these findings further. DA - 2014-03 DB - ResearchSpace DP - CSIR KW - Oceanography KW - Intra-seasonal dynamics KW - Climate research KW - Synoptic scales KW - Sub Antarctic Zone KW - SAZ KW - ÉO2/Ar ratios LK - https://researchspace.csir.co.za PY - 2014 SM - 1810-6277 T1 - The sensitivity of primary productivity to intra-seasonal mixed layer variability in the sub-Antarctic Zone of the Atlantic Ocean TI - The sensitivity of primary productivity to intra-seasonal mixed layer variability in the sub-Antarctic Zone of the Atlantic Ocean UR - http://hdl.handle.net/10204/7491 ER -