Role of Oceanic Internal Instability in the Generation of Low‐Frequency Variability in the Indian Ocean
Role of Oceanic Internal Instability in the Generation of Low‐Frequency Variability in the Indian Ocean
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DOI：
10.1029/2022gl102489
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发表时间：
2023-05
影响因子：
5.2
通讯作者：
S. Anjana;A. Chatterjee;W. Han;S. Prerna;C. K. Sajidh
中科院分区：
文献类型：
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作者：
S. Anjana;A. Chatterjee;W. Han;S. Prerna;C. K. Sajidh
印度洋海表温度（SST）的低频（年际及更长时间尺度）变化在影响区域气候方面起着至关重要的作用。通过高分辨率全球模式模拟，我们表明海洋内部变率是南印度洋副热带 - 中纬度（20°S - 40°S）观测到的低频变化的一个重要原因，与基于较粗分辨率印度洋区域模式的早期估计相比，低频活跃内部变率的纬度带明显向南偏移。值得注意的是，我们表明内部变率对塞舌尔 - 查戈斯温跃层脊区域观测到的低频变化没有贡献。能量收支分析表明，斜压不稳定是内部变率的主要原因。低频和较长空间尺度下缓慢增长的斜压不稳定有利于罗斯贝波的产生，使海表温度和海平面异常信号向西传播。
Low‐frequency (Interannual and longer timescale) variability in sea surface temperature (SST) of the Indian Ocean plays a crucial role in affecting the regional climate. Using a high‐resolution global model simulation, we show that internal oceanic variability is an important cause of the observed low‐frequency variability in the subtropical‐midlatitude south Indian Ocean (SIO) between 20° and 40°S, a marked southward shift in the latitude band of active internal variability for the low‐frequency compared to earlier estimates based on coarser Indian Ocean regional models. Notably, we show that internal variability does not contribute to the observed low‐frequency variability in the Seychelles−Chagos thermocline ridge region. Energy budget analysis shows that baroclinic instability is the primary cause for the internal variability. The slowly growing baroclinic instabilities at low frequency and longer length scale favor Rossby waves' generation, propagating the SST and sea level anomaly signals westward.