Baja California边缘PC14岩芯海水表层温度及生产力变化的百年尺度记录

CENTENNIAL VARIATIONS IN SEA SURFACE TEMPERATURE AND RODUCTIVITY OVER THE LAST 14ka FROM CORE PC-14 OFF BAJA CALIFORNIA

加利福尼亚流是北太平洋环流的重要组成部分,它的变化对全球气候及碳循环有重要影响。对位于东北太平洋低纬区Baja California外海的PC14柱状样进行了有机地球化学分析,重建了过去14ka来这一地区百年尺度的海水表面温度及生产力变化,发现其存在明显的B/A(Bling-Aller)和YD(Younger Drays)事件,但B/A和YD事件温度变化幅度小于中纬度地区。与中纬度加利福尼亚流系早中全新世温度降低不同,PC14全新世温度无明显变化趋势。这些结果表明了东太平洋低纬地区对高纬地区的气候响应以及沿岸上升流和ENSO现象对加利福尼亚流系中纬和低纬地区的影响不同。从冰消期到全新世,PC14生产力呈现阶段上升趋势,指示了由E1 Ni?o气候向La Ni?a气候的转化以及沿岸上升流加强的总体趋势。在全新世中后期(6.5—3.8ka)生产力的降低,则可能是受ENSO加强的影响。在B/A暖期,PC14生产力增加不多,但氧最小层强度增加,这表明生产力变化不是东太平洋边缘海的氧最小层强化的控制因素。

As an important component of the North Pacific gyre, the California Current affects importantly the global climate and carbon cycle. Organic geochemical survey was carried out on Core PC-14 taken from low-latitude northeast Pacific off Baja California to reconstruct centennial changes in sea surface temperature （SST） and productivity over the last 14 ka. Both B/A （Bling-Aller） and YD （Younger Drays） events were clearly revealed on the SST record, but the magnitudes of the SST change were smaller than those recorded in the cores from the mid-latitude NE Pacific. Unlike the decreasing trend in the mid-latitude California margins, the PC-14 SST record for the Holocene did not show any obvious changes. The results indicate that the low-latitude eastern Pacific responded to the climate forcing from high latitude in millennial scale, and confirm that low- and mid-latitude eastern Pacific was affected mainly by upwelling and ENSO in different ways. In terms of productivity, an overall increasing trend was shown in PC-14 from the deglaciation （14.0-11.6ka） to the Holocene, reflecting a climate transition from an E1 Nifio-dominated climate to a La Nifia-dominated climate with increased upwelling, while a decrease was included from the middle to late Holocene （6.5-3.8 ka） that was probably caused by the intensified ENSO. During the B/A warm period, the productivity increased slighdy but oxygen minimum zone （OMZ） intensified significantly, suggesting that OMZ variation in this region was irrelevant to the productivity change.