Körner Mareike, Brandt Peter, Dengler Marcus
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.
College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA.
Sci Rep. 2024 Nov 9;14(1):27400. doi: 10.1038/s41598-024-77917-2.
The tropical Angolan upwelling system (tAUS) is a highly productive ecosystem of great socio-economic importance. Productivity peaks in austral winter and is linked to the passage of remotely forced upwelling coastal trapped waves (CTWs), where the strength of the productivity peak is associated with the amplitude of the upwelling CTW. Here, we analyze the year-to-year variability in the timing and amplitude of the austral winter upwelling CTW by examining sea surface temperature, sea level anomaly, and wind fields. Our results show that the timing of the CTW is influenced by variability in the equatorial region and along the southern African coast. Weaker equatorial easterlies from April to July delay the generation of the upwelling Kelvin wave, leading to a later arrival of the upwelling CTW. In contrast, the amplitude of the CTW is primarily influenced by variability in the eastern equatorial Atlantic and the central South Atlantic, where the South Atlantic Anticyclone is located. A cooling in the eastern equatorial Atlantic three to four months before the arrival of the CTW causes stronger zonal winds, ultimately leading to a stronger austral winter upwelling CTW. Our results suggest that the timing and amplitude of the upwelling CTW in the tAUS during austral winter are predictable on seasonal time scales.
热带安哥拉上升流系统（tAUS）是一个具有高度生产力且具有重大社会经济意义的生态系统。生产力在南半球冬季达到峰值，并与远程强迫上升流沿岸捕获波（CTW）的通过有关，生产力峰值的强度与上升流CTW的振幅相关。在此，我们通过研究海表温度、海平面异常和风场来分析南半球冬季上升流CTW的时间和振幅的年际变化。我们的结果表明，CTW的时间受到赤道地区和非洲南部海岸变化的影响。4月至7月较弱的赤道东风会延迟上升流开尔文波的产生，导致上升流CTW的到来更晚。相比之下，CTW的振幅主要受到赤道大西洋东部和南大西洋中部（南大西洋反气旋所在位置）变化的影响。CTW到来前三到四个月赤道大西洋东部的降温会导致更强的纬向风，最终导致更强的南半球冬季上升流CTW。我们的结果表明，南半球冬季tAUS中上升流CTW的时间和振幅在季节时间尺度上是可预测的。
