最新研究表明，自2016年南极海冰急剧减少以来，长期维持“变淡”趋势的南极中层水（AIW）迅速转为更咸、密度更大且位置更深 1。这一位于海面下约700至1200米处的水体层，此前形成限制热量交换的屏障 1。然而，该反转可能削弱海洋阻挡地表热量进入深层的能力，从而对全球气候产生未知影响 1。
在2016年之前，南极中层水持续变淡；2016年后因海冰减少导致融水供应崩溃，水体迅速变咸、密度增加且下沉更深 1。该研究基于Argo计划20年的数据，并与卫星海冰观测及2004-2024年的其他海洋研究进行交叉验证 1。其中，南大西洋区域的变化最为显著 1。
海洋吸收了气候系统中超过90%的多余热量，其内部循环和储热能力的改变将塑造未来几十年的气候变化 1。科学家呼吁加强观测并大幅削减温室气体排放以应对潜在的持续性变化 1。
Recent research indicates that a critical barrier within the Southern Ocean, which had long helped shield deeper waters from surface warming, underwent a dramatic reversal starting in 2016 1. This shift suggests that the ocean’s capacity to absorb excess heat may be diminishing, raising concerns about future global climate impacts 1. Scientists warn that without strengthened observation and significant reductions in greenhouse gas emissions, the consequences of this change remain uncertain 1.
The phenomenon centers on Antarctic Intermediate Water (AIW), located approximately 700 to 1,200 meters beneath the sea surface 1. For years prior to 2016, this water mass followed a trend of becoming fresher 1. However, following a sharp decline in Antarctic sea ice in 2016, the supply of freshwater collapsed, causing the AIW to rapidly become saltier, denser, and positioned deeper than before 1. This transition was most pronounced in the South Atlantic region 1.
These findings are based on two decades of data from the Argo program, cross-validated with satellite observations of sea ice and other oceanographic studies conducted between 2004 and 2024 1. The implications are significant because the ocean has absorbed more than 90% of the excess heat in the climate system 1. Changes in internal circulation and heat storage capabilities will fundamentally shape climate evolution over the coming decades 1.
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