北印度洋障碍层厚度气候态和季节变化特征及其成因初步分析

基于2004—2018年Argo (Array for Real-Time Geostrophic Oceanography)浮标观测的温度、盐度数据, 利用经验正交函数(EOF)分析和小波分析等方法对北印度洋(40°—105°E, 5°S—25°N)障碍层时空分布特征进行分析。结果显示: 北印度洋的东部常年存在障碍层, 而西部障碍层出现的概率相对较低; 较厚的障碍层出现在阿拉伯海东南部(67°—75°E, 3°—12°N)、孟加拉湾(82°—93°E, 11°—20°N)和赤道东印度洋(81°—102°E, 4°S—3°N)。阿拉伯海东南部和孟加拉湾障碍层厚度以年变化为主, 且呈同位相变化, 均为冬季最大, 夏季最小。赤道东印度洋区域则主要呈现半年周期变化, 在夏季和冬季各出现一次峰值。进一步分析表明, 孟加拉湾和赤道东印度洋障碍层厚度主要受等温层深度变化影响, 混合层深度变化对障碍层厚度变化的影响相对较小; 阿拉伯海障碍层厚度同时受等温层深度变化和混合层深度变化影响, 其中等温层深度变化对其影响更大。

Preliminary analysis on climatological and seasonal variation of barrier layer thickness in the northern Indian Ocean and it’s mechanism

Based on the Array for Real-Time Geostrophic Oceanography (Argo) temperature and salinity observations from 2004 to 2018, we studies the spatial and temporal variations of the barrier layer in the Northern Indian Ocean (40°—105°E, 5°S—25°N) by using EOF (Empirical Orthogonal Function) analysis, wavelet analysis and other methods. The results show that barrier layer exists in the eastern Indian Ocean all year round, but the probability of its occurrence in the western Indian Ocean is low. Thick barriers appear mainly in the south-eastern Arabian Sea (67°—75°E, 3°—12°N), Bay of Bengal (82°—93°E, 11°—20°N) and eastern equatorial Indian Ocean (81°—102°E, 4°S—3°N). The thickness of the barrier layer, which is present in the southeast Arabian Sea and Bay of Bengal, exhibits remarkable annual variation with the largest value in winter and the smallest in summer. In the eastern equatorial Indian Ocean, there is a semi-annual cycle, with peaks in summer and winter. Further analysis shows that the thickness of the barrier layer in the Bay of Bengal and eastern equatorial Indian Ocean is mainly affected by the change of isothermal layer depth, while the change of mixed layer depth has little effect on the change of barrier layer thickness. The thickness of the barrier layer in the Arabian Sea is affected by the changes of both isothermal layer depth and mixed layer depth, of which the isothermal layer depth has a greater influence on it.