Trends in coastal upwelling intensity during the late 20th century
Trends in coastal upwelling intensity during the late 20th century
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DOI：
10.5194/os-6-815-2010
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发表时间：
2010-01-01
期刊：
影响因子：
3.2
通讯作者：
Schulz, M.
中科院分区：
文献类型：
--
作者：
Narayan, N.;Paul, A.;Schulz, M.
本文利用经向风应力和海面温度的各种上升流指数，研究了20世纪后半叶（1960-2001）沿海上升流强度的线性变化趋势。这项分析是在世界上四个主要的沿海上升流地区进行的，它们是西北非洲、吕德里茨、加利福尼亚和秘鲁。经向风应力强度的变化趋势在1960—2001年呈稳定增长趋势，这也反映在同期海温指数上。在加利福尼亚海温仪器记录中观测到的稳定冷却进一步证实了这一观测结果。还注意到，从不同数据集获得的经向风应力趋势彼此有很大差异。相关分析表明，大西洋多年代际涛动（AMO）和太平洋年代际涛动（PDO）等海盆尺度振荡不能直接与观测到的西北非洲和加利福尼亚上升流强度的增加联系起来。由于北大西洋涛动指数与经向风应力呈负相关，而与海温指数缺乏相关性，北大西洋涛动（NAO）与西北非洲沿海上升流的关系变得模糊。我们的研究结果进一步支持了全球沿海上升流强度增加的假设，这是由于大气中温室气体浓度的增加以及与之相关的海陆压力梯度和经向风应力的增加。
This study presents linear trends of coastal upwelling intensity in the later part of the 20th century (1960-2001) employing various indices of upwelling, derived from meridional wind stress and sea surface temperature. The analysis was conducted in the four major coastal upwelling regions in the world, which are off North-West Africa, Luderitz, California and Peru. The trends in meridional wind stress showed a steady increase of intensity from 1960-2001, which was also reflected in the SST index calculated for the same time period. The steady cooling observed in the instrumental records of SST off California substantiated this observation further. It was also noted that the trends in meridional wind stress obtained from different datasets differ substantially from each other. Correlation analysis showedthat basin-scale oscillations like the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) could not be directly linked to the observed increase of upwelling intensity off NW Africa and California respectively. The relationship of the North Atlantic Oscillation (NAO) with coastal upwelling off NW Africa turned out to be ambiguous due to a negative correlation between the NAO index and the meridional wind stress and a lack of correlation with the SST index. Our results give additional support to the hypothesis that the coastal upwelling intensity increases globally because of raising greenhouse gas concentrations in the atmosphere and an associated increase of the land-sea pressure gradient and meridional wind stress.