To better understand the impact of climate change on the Southern Ocean (SO) biogeochemistry, we must know the evolution of the seasonal cycle of biological properties. Here we present the first estimate of the seasonal evolution of chlorophyll-a (Chl-a) along oceanic fronts in the Indian sector of SO using Bio-Argo float observations. The present study is based on data collected using three such floats deployed in the frontal zones. The high productivity is usually attributed to the upwelling of nutrient-enriched subsurface water, the supply of dissolved iron to the ocean surface and their horizontal advection. Our analysis shows that the seasonal evolution of Chl-a is similar in all the three frontal regions, namely Sub-Tropical front (STF), Sub-Antarctic Front (SAF) and Polar Front (PF). We also found that shoaling of the Mixed Layer Depth (MLD) above the critical depth, owing to an increase in light exposure during spring, triggers the initiation of the spring bloom.

为了更好地了解气候变化对南部海洋（SO）生物地球化学的影响，我们必须知道生物特性的季节性周期的演变。在这里，我们使用Bio-Argo浮法观测资料，对印度SO区沿海洋前沿叶绿素a（Chl- a）的季节性演变进行了首次估计。本研究基于使用部署在额叶区域中的三个此类浮标收集的数据。高生产率通常归因于富含营养的地下水的上升流，向海洋表面的溶解铁的供应及其水平对流。我们的分析表明Chl-的季节变化一在三个亚热带锋面（STF），南极亚热带锋面（SAF）和极地锋面（PF）这三个额叶区域都相似。我们还发现，由于春季期间曝光量的增加，超过临界深度的混合层深度（MLD）的浅滩触发了春季开花的开始。