黑潮延伸体海域亚中尺度垂向热量输运的季节变化特征

Seasonal variability of submesoscale vertical heat transport in the Kuroshio Extension

亚中尺度过程伴随着强烈的垂向速度,显著影响着海洋表面与海洋内部之间热量、浮力和质量等示踪物的垂向输运。基于(1/48)°的LLC4320模式结果,本文对黑潮延伸体海域亚中尺度垂向热量输运的季节变化进行了研究。研究结果表明,黑潮延伸体海域亚中尺度垂向热量输运具有明显的春冬强、夏秋弱的季节变化特征。上层海洋净亚中尺度垂向热通量变化与混合层深度变化趋势较为一致,在混合层上方整体呈现出向上的亚中尺度热量输运,混合层下方也存在很强的亚中尺度垂向热量输运,但呈现正负交替的变化特征,净亚中尺度垂向热量输运较小。垂向热通量波数频率协同谱分析表明,混合层下方的亚中尺度垂向热量输运可能是由线性内波引起的,但线性内波引起的向上与向下的垂向热量输运相互抵消,在季节平均后净垂向热量输运较小。

Submesoscale processes associated with strong vertical velocities play significant roles in the vertical transport of tracers between the ocean surface and the interior,including heat,buoyancy,and mass.Based on the results of the(1/48)° LLC4320 model,this study investigates the seasonal variations of submesoscale vertical heat transport in the Kuroshio Extension.The results show that submesoscale vertical heat transport in the Kuroshio Extension exhibits distinct seasonal variations,with strong transport in spring and winter,and weaker transport in summer and autumn.The variation of net submesoscale vertical heat flux in the upper ocean is consistent with the trend of mixed layer depth,which shows overall upward submesoscale heat transport above the mixed layer and strong alternating positive and negative submesoscale vertical heat transport below the mixed layer,resulting in relatively small net submesoscale vertical heat transport.Coherent spectral analysis of vertical heat flux wavenumberfrequency suggests that submesoscale vertical heat transport below the mixed layer may be caused by linear internal waves,but the upward and downward vertical heat transports induced by linear internal waves counteract each other,leading to a reduced net vertical heat transport after averaging over the season.