In the Oyashio region, remarkable climatic signals are observed in biogeochemical parameters such as phosphate (PO₄) concentration and debate continues regarding possible causes. Using a regional ice–ocean coupled model with a simple biogeochemical cycle, this study investigated the mechanisms controlling interannual–decadal variations in surface PO₄ in the Oyashio region and their relationships to climate change. Hindcast experiments forced with atmospheric reanalysis data for 1980–2010 and 18.6-year tidal mixing strength in the Kuril Straits qualitatively simulated interannual–decadal variations of surface PO₄, including a realistic seasonal cycle. Interannual fluctuations of simulated PO₄ in the Oyashio region are prominent in winter and characterized by year-to-year variability. Budget analysis of PO₄ in the mixed layer showed that the wintertime increase in PO₄ is caused by lateral advection as well as by local vertical convection. The geostrophic current variability responsible for lateral advection of PO₄ is related primarily to the barotropic response of arrested topographic waves in the Sea of Okhotsk as well as the wind-driven gyre in the North Pacific, both of which are regulated by the strength of the wintertime monsoon atmospheric pattern. On a decadal timescale (>7 years), temporal variations of surface PO₄ in the Oyashio region are characterized by decadal-scale fluctuation with positive (negative) peaks around 1985, 1995, and 2005 (1990 and 2000). A series of sensitivity experiments demonstrated that the decadal variability of PO₄ is largely explained by atmospheric wind conditions; however, modulation by 18.6-year tidal mixing is not negligible. Diagnostic analysis of wind-forced-experiment data revealed that the decadal PO₄ signal is advected from the Sea of Okhotsk, where 8-year leading wintertime Ekman upwelling supplies PO₄-rich water in the northern shelf region, and that the responsible atmospheric circulation is related to the West Pacific pattern. Our model simulation suggests that the wintertime wind-driven current system in the Sea of Okhotsk is important to the system feeding surface nutrients into the Oyashio region on an interannual–decadal timescale.

在亲潮地区，在磷酸盐 (PO ₄ ) 浓度等生物地球化学参数中观察到了显着的气候信号，关于可能原因的争论仍在继续。本研究使用具有简单生物地球化学循环的区域冰海耦合模型，研究了控制亲潮地区地表 PO ₄年际-年代际变化的机制及其与气候变化的关系。使用 1980-2010 年大气再分析数据和千岛海峡 18.6 年潮汐混合强度进行的后报实验定性模拟了地表 PO _{4 的}年际-年代际变化，包括真实的季节周期。模拟 PO _{4 的}年际波动Oyashio 地区在冬季尤为突出，并且具有逐年变化的特点。混合层中PO _{4 的}预算分析表明，冬季PO _{4 的}增加是由横向平流和局部垂直对流引起的。造成 PO ₄横向平流的地转洋流变化主要与鄂霍次克海被截留的地形波的正压响应以及北太平洋的风驱动环流有关，两者都受大气强度的调节。冬季季风大气模式。在十年时间尺度上（>7 年），地表 PO _{4 的}时间变化亲潮地区的 1985 年、1995 年和 2005 年（1990 年和 2000 年）前后具有正（负）峰的年代际尺度波动。一系列敏感性实验表明，PO ₄的年代际变化在很大程度上是由大气风况解释的；然而，18.6 年潮汐混合的调制不容忽视。对风力实验数据的诊断分析表明，十年期 PO ₄信号来自鄂霍次克海，在那里 8 年领先的冬季 Ekman 上升流供应 PO ₄-北部陆架区富含水，负责的大气环流与西太平洋模式有关。我们的模型模拟表明，鄂霍次克海的冬季风驱动电流系统对于在年际-年代际时间尺度上将地表养分输送到亲潮地区的系统很重要。