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首页> 外文期刊>Journal of oceanography >Has the 1998 regime shift also occurred in the oceanographic conditions and lower trophic ecosystem of the Oyashio region?
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Has the 1998 regime shift also occurred in the oceanographic conditions and lower trophic ecosystem of the Oyashio region?

机译：Oyashio地区的海洋条件和较低营养生态系统是否也发生了1998年政权转移？

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To examine whether the regime shift in 1998 that has been variously reported to have occurred in the oceanographic conditions of the central and eastern North Pacific also occurred in the Oyashio region, western North Pacific, we compared data over the period 1990–2003. Oceanographic conditions were compared before 1997 with those after 1998, using the A-line dataset (1990–2003) obtained by the oceanographic surveys of the Hokkaido National Fisheries Research Institute, Fisheries Research Agency (HNFRI/FRA). Seasonal changes of the monthly-mean SST (as temperature in the surface layer) show a significant increase in spring after 1998. After 1998, the mean concentration of chlorophyll a at the surface was higher in spring than that before 1997. This was more remarkable in the main current of the Oyashio. These changes suggest that the spring phytoplankton bloom in the Oyashio region after 1998 was larger in magnitude and initiated earlier. Consumption of nutrients during the spring bloom and standing stock of netplankton also shows a distinct difference between the time period before 1997 and after 1998. These results support the occurrence of the regime shift around 1998 in the Oyashio region. The changes of hydrographical conditions accompanying with the 1998 regime shift are discussed. The hydrographic mechanism of enhancement of primary productivity during the spring phytoplankton bloom was not fully clarified, though. Results in this study may support the usefulness of the A-line dataset for analysis of long-term variability in the western subarctic Pacific.
机译：为了研究在北太平洋中部和东部的海洋条件下是否发生了1998年的政权更替（据报道发生在北太平洋中部和东部）是否也发生在我们的研究中，我们比较了1990-2003年期间的数据。利用由渔业研究机构北海道国家渔业研究所的海洋学调查获得的A线数据集（1990-2003年）对1997年之前和1998年之后的海洋条件进行了比较。 1998年以后的春季，每月平均SST的季节变化（作为表层温度）显示出明显的增加。1998年以后，春季的表层叶绿素a的平均浓度高于1997年之前的水平。在Oyashio的主要潮流中。这些变化表明，1998年以后的Oyashio地区春季浮游植物的花期较大，而且开始较早。春季开花和浮游植物立足量期间的养分消耗在1997年之前和1998年之后之间也显示出明显的差异。这些结果支持了Oyashio地区1998年左右政权转移的发生。讨论了水文条件随1998年政权变更而发生的变化。不过，尚未完全阐明春季浮游植物开花期间提高初级生产力的水文机理。这项研究的结果可能支持A线数据集对于分析北极西太平洋太平洋长期变化的有用性。

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