Influence of North Pacific subtropical mode water variability on the surface mixed layer through the heaving of the upper thermocline on decadal timescales

被引:0
作者
Fumiaki Kobashi
Norihisa Usui
Nanami Akimoto
Naoto Iwasaka
Toshio Suga
Eitarou Oka
机构
[1] Tokyo University of Marine Science and Technology,Graduate School of Science
[2] Meteorological Research Institute,Atmosphere and Ocean Research Institute
[3] Tohoku University,undefined
[4] The University of Tokyo,undefined
来源
Journal of Oceanography | 2023年 / 79卷
关键词
North Pacific subtropical mode water; Thermocline; Mixed layer; Decadal variations; Reemergence phenomenon;
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学科分类号
摘要
Decadal variability of the North Pacific subtropical mode water (STMW) and its influence on the upper thermocline and mixed layer are examined in a four-dimensional variational ocean re-analysis for the Western North Pacific over 30 years (FORA–WNP30). The STMW that forms south of the Kuroshio Extension becomes thick/cold and thin/warm on decadal timescales. These variations are subducted and advected to the south, where thick (thin) STMW causes the upper thermocline to heave up (down) above the STMW, producing cold (warm) temperature anomalies at subsurface depths, with especially large anomalies at the depths of the seasonal thermocline. Temperature anomalies also appear in the mixed layer from March to November, except in September. These anomalies have the same sign as the temperature anomalies of the STMW, although they are due not to the reemergence of the STMW at the surface but to the heaving of the upper thermocline. In the FORA–WNP30, because the formation of the mixed layer temperature anomalies owes much to the increment introduced by data assimilation, the mechanism remains unclear. A heat budget analysis of the mixed layer, however, suggests the importance of entrainment and/or vertical diffusion at the base of the mixed layer for conveying temperature anomalies from the upper thermocline to the mixed layer. The STMW also affects the mixed layer depth. A thick (thin) STMW shoals (deepens) the seasonal thermocline, enhancing (weakening) stratification at depths below the mixed layer and thus hindering (favoring) mixed layer development from July to September.
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页码:379 / 394
页数:15
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共 208 条
[1]  
Alexander MA(1995)A mechanism for the recurrence of wintertime midlatitude SST anomalies J Phys Oceanogr 25 122-137
[2]  
Deser C(1999)The reemergence of SST anomalies in the North Pacific Ocean J Climate 12 2419-2433
[3]  
Alexander MA(1992)Formation and spreading of subtropical mode water in the North Pacific J Geophys Res 97 11177-11189
[4]  
Deser C(2005)The ventilated pool: a model of subtropical mode water J Phys Oceanogr 35 137-150
[5]  
Timlin MS(1998)Effects of interdecadal climate variability on the oceanic ecosystems of the NE Pacific Fish Oceanogr 7 1-21
[6]  
Bingham FM(2004)‘Reemergence’ areas of winter sea surface temperature anomalies in the world's oceans Geophys Res Lett 31 L10303-787
[7]  
Dewar WK(2010)Improved description of global mixed-layer depth using Argo profiling floats J Oceanogr 66 773-1622
[8]  
Samelson RM(1994)Three-dimensional structure of the wind-driven circulation in the subtropical North Pacific J Phys Oceanogr 24 1608-3117
[9]  
Vallis GK(1995)Variations of current path, velocity, and volume transport of the Kuroshio in relation with the large meander J Phys Oceanogr 25 3103-43
[10]  
Francis RC(2012)Review on North Pacific subtropical countercurrents and subtropical fronts: role of mode waters in ocean circulation and climate J Oceanogr 68 21-503