Record low Arctic sea ice extent in 2012 linked to two-year La Niña-driven sea surface temperature pattern

Arctic summer sea ice decline accelerated from the mid-2000s to 2012, with the 2012 record low remaining unbroken. While frequent La Niña events during this period have been suggested as a driver of this trend acceleration, no convincing evidence has been presented. Here, using a climate model nudged to observed pan-tropical sea surface temperatures (SST), we show that the back-to-back La Niña events during 2010–2011, followed by a North Pacific cooling and a marginal El Niño, were a key contribution to the 2012 record low. Specifically, the La Niña events in 2010–2011 warmed the Arctic Pacific sector, whereas tropical SST anomalies in 2012 strengthened the Greenland high pressure, leading to an Arctic dipole-like pressure pattern and strengthening of transpolar ice drift. These Arctic temperature and circulation anomalies led to the record low sea ice extent in 2012, highlighting the strong influence of tropical SSTs on Arctic climate.2000年代中期至2012年，北极夏季海冰范围消退速率显著加快，且2012年创下的海冰范围最低纪录至今未被突破。尽管有研究提出，该时期频发的拉尼娜（La Niña）事件是海冰消退速率加快的驱动因素，但迄今尚未有令人信服的证据支撑这一观点。本研究采用基于观测泛热带海表温度（SST）进行逼化的气候模式，分析表明2010—2011年连续发生的拉尼娜事件，叠加随后的北太平洋降温与弱厄尔尼诺（El Niño）事件，是导致2012年海冰范围创历史新低的关键诱因。具体而言，2010—2011年的拉尼娜事件使北极太平洋扇区升温；而2012年的热带海表温度异常则增强了格陵兰高压系统，进而形成北极偶极型气压模态，并强化了跨极冰漂流运动。上述北极温度与环流异常共同促成了2012年的海冰范围历史新低，凸显了热带海表温度对北极气候的强烈调控作用。