Graduate Program in Oceanography, Federal University of Santa Catarina, Box 476, Florianópolis, SC, 88040-900, Brazil.
Griffith Centre for Coastal Management (GCCM), Building G51, Griffith University, Gold Coast, QLD, 4215, Australia.
Sci Rep. 2020 Oct 29;10(1):18553. doi: 10.1038/s41598-020-75265-5.
Through alteration of wave-generating atmospheric systems, global climate changes play a fundamental role in regional wave climate. However, long-term wave-climate cycles and their associated forcing mechanisms remain poorly constrained, in part due to a relative dearth of highly resolved archives. Here we use the morphology of former shorelines preserved in beach-foredune ridges (BFR) within a protected embayment to reconstruct changes in predominant wave directions in the Subtropical South Atlantic during the last ~ 3000 years. These analyses reveal multi-centennial cycles of oscillation in predominant wave direction in accordance with stronger (weaker) South Atlantic mid- to high-latitudes mean sea-level pressure gradient and zonal westerly winds, favouring wave generation zones in higher (lower) latitudes and consequent southerly (easterly) wave components. We identify the Southern Annular Mode as the primary climate driver responsible for these changes. Long-term variations in interhemispheric surface temperature anomalies coexist with oscillations in wave direction, which indicates the influence of temperature-driven atmospheric teleconnections on wave-generation cycles. These results provide a novel geomorphic proxy for paleoenvironmental reconstructions and present new insights into the role of global multi-decadal to multi-centennial climate variability in controlling coastal-ocean wave climate.
通过改变产生波浪的大气系统，全球气候变化在区域波浪气候中起着根本性的作用。然而，长期的波浪气候循环及其相关的强迫机制仍然受到很大的限制，部分原因是缺乏高度解析的档案。在这里，我们利用保护海湾内的海滩前沙丘脊（BFR）中保存的前海岸线形态，来重建过去约 3000 年来南大西洋亚热带地区主要波浪方向的变化。这些分析显示，主要波浪方向存在多百年的振荡周期，与南大西洋中高纬度平均海平面气压梯度和纬向西风的增强（减弱）一致，有利于生成波浪的区域在较高（较低）纬度，从而产生南向（东向）的波浪分量。我们确定南极涛动是导致这些变化的主要气候驱动因素。半球间表面温度异常的长期变化与波浪方向的振荡并存，这表明温度驱动的大气遥相关对波浪生成周期的影响。这些结果为古环境重建提供了一种新的地貌学代理，并为控制沿海-海洋波浪气候的全球数十年到百年气候变率的作用提供了新的见解。
