The dominant role of the Indian Ocean Dipole in shaping the barotropic structure of Indonesian throughflow outflow interannual variability: Insights from the 2006–2007 positive Indian Ocean Dipole events

The Indonesian Throughflow (ITF) outflow channels are influenced by the combined effects of El Niño–Southern Oscillation and the Indian Ocean Dipole (IOD), making it difficult to quantify their individual climatic contributions using traditional linear methods. To address this issue, multiple high-resolution reanalysis datasets and a random forest (RF) model are utilized to attribute dominant climate drivers and quantify their relative importance. Results show that in 2001–2010, the IOD dominates the variability of ITF outflow, which shows barotropic structures. The consecutive positive IOD events (2006–2007) enhance the upper-layer volume, heat, and freshwater transport into the Indian Ocean, driven by an intensified inter-ocean pressure gradient; Concurrently, wave-induced dynamical adjustments suppress lower-layer outflow and diminish corresponding heat and freshwater exports. The RF approach provides a novel pathway for improved attribution of climatic effects on ocean circulation and supports better modeling of the ITF. 摘要 印尼贯穿流 (Indonesian Throughflow, ITF) 出流通道受到厄尔尼诺-南方振荡 (El Niño–Southern Oscillation, ENSO) 与印度洋偶极子 (Indian Ocean Dipole, IOD) 的共同影响, 而传统线性方法难以量化二者对ITF的相对贡献. 为此, 本研究联合多套高分辨率再分析数据集与随机森林 (random forest, RF) 模型, 识别主导气候因子并量化其相对重要性. 结果表明, 在2001–2010年期间, IOD主导了ITF出流的年际变率, 且呈正压结构. 连续发生的正IOD事件 (2006–2007年) 通过增大洋际间压力梯度, 增强了向印度洋输送的上层水体, 热量和淡水; 与此同时, 通过波动动力调整抑制了下层水体, 热量与淡水输送. RF方法为归因分析不同气候因子影响下的海洋环流变化提供了新途径, 且有助于进一步完善对ITF的模拟.