The State of the California Current, 1996-1997: Mixed Signals from the Tropics
The State of the California Current, 1996-1997: Mixed Signals from the Tropics
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1996-1997 年加利福尼亚洋流状况：来自热带的混合信号
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
K. Sakuma
中科院分区：
文献类型：
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作者：
T. Hayward;Affonso S. Mascarenas;S. Castillo;F. Chavez;F. Schwing;K. Baltz;S. Cummings;A. W. Mantyla;T. Murphree;D. Ainley;K. Sakuma
来自加利福尼亚海流区域的大量数据集，以及影响该区域的大型场，可用于及时评估该系统中最近的环境条件。除了长期运行的季度CalCOFI巡航，其中包括RV Roger Revelle的初步研究巡航，下加利福尼亚和加利福尼亚中部的几项调查提供了与当前CalCOFI覆盖范围相邻的沿海地区的信息。对1996- 1997年期间整个北太平洋和加利福尼亚海流的情况进行了总结和解释。自1995年后期以来，中等至较弱的拉尼娜现象影响了北太平洋。但与其他拉尼娜事件相比，这次特殊的拉尼娜事件显示了热带太平洋大气加热的不寻常模式。这可能有助于在北太平洋产生不同的反应，在几个重要方面，不同于典型的拉尼娜。最显著的差异是风异常，这可能导致了这一时期加利福尼亚和墨西哥近海相对较高的海平面和温暖的海温。厄尔尼诺现象于1997年初开始在热带地区发展。如果这一事件继续发展，预计将对加州海流地区产生重大影响。沿海条件的变化是复杂的，似乎是由于大尺度大气和海洋强迫中的局部过程和异常的综合影响。沿海指数和时间序列显示DAVID G. AINLEY H. T. Harvey and Associates 906 Elizabeth Street Alviso, California 9.5002的变率没有主导模式，其长期季节平均值的异常通常不显著。上升流指数和浮标时间序列表明，1996年春夏季上升流普遍较高，1997年初上升流率异常高。1997年5月，整个海岸的上升流急剧减少。在S I 0码头，海温在一九九六年上半年异常温暖，但在一九九六年年底及一九九七年年初较接近正常温度。1997年春季，海温和沿海海平面异常开始增加，但说这与厄尔尼诺强迫有关还为时过早。可以肯定的是，早在最近这次明显的厄尔尼诺现象出现之前，该地区就已经观测到类似厄尔尼诺现象的温暖气候。由于陆上风和高淡水流量，冬季海平面高度相对较高，这与拉尼娜现象导致的横跨整个北太平洋的正高度异常有关。1996- 1997年观测到的海洋环流模式与长期平均值相似，并且自1996年初以来具有相对较高的中尺度活动。加利福尼亚洋流核心的盐度明显低于历史气候学所显示的。1996年8月、10月和1997年4月，在南加州和1996年6月，在大苏尔海岸发现了一股强烈的沿海逆流。叶绿素含量低的温暖盐水与这种流动有关。尽管基于叶绿素浓度的初级产量相当高，但与历史水平相比，大型浮游动物生物量仍然很低
A large number of data sets from within the California Current region, and the large-scale fields that affect this region, are available for timely assessment of recent environmental conditions in this system. In addition to the long-running quarterly CalCOFI cruises, which featured the initial research cruise of RV Roger Revelle, several surveys off Baja California and central California have provided information on coastal areas adjacent to the present CalCOFI coverage. Conditions throughout the north Pacific and in the California Current are summarized and interpreted for the 1996-97 period. Moderate to weak La Niiia conditions have affected the north Pacific since late 1995. But this particular La Niiia event displayed an unusual pattern of atmospheric heating in the tropical Pacific, compared to other La Niiia events. Ths may have helped produce a different response over the north Pacific that was, in several important respects, different from a typical La Niiia. The most notable differences were in the wind anomalies, which may have contributed to relatively high sea level and warm SSTs offshore of California and Mexico throughout this period. El Niiio condtions began to develop in the tropics in early 1997. If this event continues to develop, significant effects on the California Current region can be expected. Variability in coastal conditions is complex, and seems due to the combined effect of local processes and anomahes in large-scale atmospheric and ocean forcing. Coastal indices and time series show no dominant pattern of DAVID G. AINLEY H. T. Harvey and Associates 906 Elizabeth Street Alviso, California 9.5002 variability, and the anomalies from their long-term seasonal means were generally not remarkable. Upwelling indices and buoy time series suggest generally high upwelling in the spring and summer of 1996, and unusually high rates in early 1997. In May 1997, upwelling was dramatically reduced along the entire coast. At S I 0 Pier, SSTs were anomalously warm during the first half of 1996, but closer to the norm in late 1996 and early 1997. In spring 1997, SST and coastal sea-level anomalies began increasing, but it is premature to say this was related to El Niiio forcing. What is certain is that warm, El Niiio-like conditions have been observed in the region long before the initial development of this latest apparent El Niiio. Winter sea-level heights were relatively high due to onshore winds and high freshwater discharge, and were connected with positive height anomalies extending across the entire north Pacific, a consequence of La Niiia. Oceanic circulation patterns observed in 1996-97 were similar to the long-term mean, and have featured relatively high mesoscale activity since early 1996. Salinities in the core of the California Current were noticeably lower than historical climatologies indicate. A strong coastal countercurrent was noted off southern California in August and October 1996 and April 1997, and along the Big Sur coast in June 1996. Warm, saline water that was low in chlorophyll was associated with this flow. Despite reasonably high primary production based on chlorophyll concentrations, macrozooplankton biomass remains very low compared to historical levels in the