Department of Atmosphere, Ocean, and Earth System Modeling Research, Meteorological Research Institute, Tsukuba, Japan.
Department of Geophysics, Graduate School of Science, Tohoku University, Sendai, Japan.
Sci Rep. 2023 Jan 5;13(1):256. doi: 10.1038/s41598-022-26879-4.
The ocean responds to atmospheric variations. Changes in sea surface winds, surface air temperature, and surface air humidity cause upper ocean variability by modulating air-sea momentum and heat exchanges. Upper ocean variability in the mid-latitudes on inter-annual and longer timescales has previously been considered to be attributable to atmospheric variations in the cold season, because atmospheric forcing is stronger in the cold season than in the warm season. However, this idea has not been sufficiently confirmed yet. Although the ocean model is a useful tool to evaluate the impact of the atmospheric forcing in each season, there are no past studies having examined ocean model responses respectively to the cold- and warm-season atmospheric forcing. In this study, we performed numerical experiments with an eddy-resolving ocean general circulation model and investigated oceanic responses to cold- and warm-season atmospheric forcing, focusing on the Kuroshio and North Pacific subtropical mode water (STMW) in the western mid-latitude North Pacific. We found that temporal variations of net Kuroshio transport and STMW distribution/temperature are dominantly controlled by atmospheric forcing in the cold season. These results suggest that cold-season atmospheric variations are key to obtaining insights into large-scale upper ocean variability in the North Pacific subtropical gyre.
海洋对大气变化有响应。海面风、地表气温和地表空气湿度的变化通过调节海气动量和热量交换，引起上层海洋的可变性。先前认为中纬度海洋上层的年际和更长时间尺度的可变性归因于冬季的大气变化，因为冬季大气强迫比夏季更强。然而，这个想法尚未得到充分证实。尽管海洋模式是评估每个季节大气强迫影响的有用工具，但没有过去的研究分别检查海洋模式对冷季和暖季大气强迫的响应。在这项研究中，我们使用一个具有涡旋分辨率的海洋环流模式进行了数值实验，研究了海洋对冷季和暖季大气强迫的响应，重点关注西北太平洋中纬度的黑潮和北太平洋亚热带模态水（STMW）。我们发现，黑潮净输送和 STMW 分布/温度的时间变化主要受冬季大气强迫控制。这些结果表明，冬季大气变化是了解北太平洋副热带环流中大规模上层海洋可变性的关键。
