Upwelling along the southeast African coastline and links to cold water temperature anomalies at Sodwana Bay, South Africa

IF 2.1 3区 地球科学 Q2 OCEANOGRAPHY Continental Shelf Research Pub Date : 2024-04-05 DOI:10.1016/j.csr.2024.105227
C. Wells, J. Pringle, D.D. Stretch
{"title":"Upwelling along the southeast African coastline and links to cold water temperature anomalies at Sodwana Bay, South Africa","authors":"C. Wells,&nbsp;J. Pringle,&nbsp;D.D. Stretch","doi":"10.1016/j.csr.2024.105227","DOIUrl":null,"url":null,"abstract":"<div><p>Coral bleaching is a major concern for the health and survival of coral reefs worldwide, as it can significantly reduce coral growth and increase coral susceptibility to disease. The coral reefs at Sodwana Bay, located on the northeastern coast of South Africa, have shown resilience to coral bleaching which has been attributed to cold water temperature anomalies observed at Sodwana. This study investigates the regional hydrodynamic processes associated with 63 temperature anomalies identified at Sodwana between 1994 and 2015. The study found that 65% of the anomalies are associated with remote upwelling of cold water near the Delagoa Peninsula, followed by advection from the Delagoa Bight towards the Sodwana region. The cold upwelled water advects directly from the peninsula along the shelf towards Sodwana or recirculates within the Delagoa Bight before advecting along the coastline to Sodwana. The remaining 35% of the anomalies were associated with local upwelling within the KwaZulu-Natal Bight south of Sodwana.</p><p>The study also found that the separation of the strong intermittent southward stream from the Delagoa Peninsula is strongly linked to the upwelling at the Delagoa Peninsula. The cold upwelled water is then advected to the Sodwana region by regional flow patterns, resulting in a temperature anomaly at Sodwana. The local upwelling is similarly linked to an increase in the Agulhas Current velocity magnitude around Sodwana and flow separation of the current from the coastline at the northern extent of the KwaZulu-Natal Bight.</p><p>The cross-correlations between the conditionally averaged flow fields associated with remote and local upwelling near the Delagoa Peninsula and the instantaneous flow fields at the time of the upwelling showed a positive correlation for all the anomalies over the 21 years. The anomalies associated with remote upwelling have an average correlation coefficient of 0.67 with a maximum correlation of 0.96. The anomalies associated with local upwelling have an average correlation coefficient of 0.74 with a maximum correlation of 0.98.</p><p>This study shows that the unique geometry of the southeast African coastline is a key factor associated with the cold water temperature anomalies at Sodwana. The interaction between the regional hydrodynamics and coastline features such as the Delagoa and Natal Bights, are crucial for the upwelling that eventually leads to the cold water temperature anomalies at Sodwana. Without these coastline features and the intermittent strengthening of the southward streams along the coastline due to the high eddy kinetic energy associated with the region, it is likely that these temperature anomalies would not occur at Sodwana. Without these temperature anomalies, the Sodwana coral reefs would become more vulnerable to climate change and coral bleaching.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1000,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0278434324000578/pdfft?md5=cf379b352347a612b58fe5268a3c4f58&pid=1-s2.0-S0278434324000578-main.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Continental Shelf Research","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0278434324000578","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"OCEANOGRAPHY","Score":null,"Total":0}
引用次数: 0

Abstract

Coral bleaching is a major concern for the health and survival of coral reefs worldwide, as it can significantly reduce coral growth and increase coral susceptibility to disease. The coral reefs at Sodwana Bay, located on the northeastern coast of South Africa, have shown resilience to coral bleaching which has been attributed to cold water temperature anomalies observed at Sodwana. This study investigates the regional hydrodynamic processes associated with 63 temperature anomalies identified at Sodwana between 1994 and 2015. The study found that 65% of the anomalies are associated with remote upwelling of cold water near the Delagoa Peninsula, followed by advection from the Delagoa Bight towards the Sodwana region. The cold upwelled water advects directly from the peninsula along the shelf towards Sodwana or recirculates within the Delagoa Bight before advecting along the coastline to Sodwana. The remaining 35% of the anomalies were associated with local upwelling within the KwaZulu-Natal Bight south of Sodwana.

The study also found that the separation of the strong intermittent southward stream from the Delagoa Peninsula is strongly linked to the upwelling at the Delagoa Peninsula. The cold upwelled water is then advected to the Sodwana region by regional flow patterns, resulting in a temperature anomaly at Sodwana. The local upwelling is similarly linked to an increase in the Agulhas Current velocity magnitude around Sodwana and flow separation of the current from the coastline at the northern extent of the KwaZulu-Natal Bight.

The cross-correlations between the conditionally averaged flow fields associated with remote and local upwelling near the Delagoa Peninsula and the instantaneous flow fields at the time of the upwelling showed a positive correlation for all the anomalies over the 21 years. The anomalies associated with remote upwelling have an average correlation coefficient of 0.67 with a maximum correlation of 0.96. The anomalies associated with local upwelling have an average correlation coefficient of 0.74 with a maximum correlation of 0.98.

This study shows that the unique geometry of the southeast African coastline is a key factor associated with the cold water temperature anomalies at Sodwana. The interaction between the regional hydrodynamics and coastline features such as the Delagoa and Natal Bights, are crucial for the upwelling that eventually leads to the cold water temperature anomalies at Sodwana. Without these coastline features and the intermittent strengthening of the southward streams along the coastline due to the high eddy kinetic energy associated with the region, it is likely that these temperature anomalies would not occur at Sodwana. Without these temperature anomalies, the Sodwana coral reefs would become more vulnerable to climate change and coral bleaching.

查看原文
分享 分享
微信好友 朋友圈 QQ好友 复制链接
本刊更多论文
东南非洲海岸线的上升流以及与南非索德瓦纳湾冷水温度异常的联系
珊瑚白化是全世界珊瑚礁健康和生存的一个主要问题,因为它会大大减少珊瑚的生长,增加珊瑚对疾病的易感性。位于南非东北海岸的索德瓦纳湾的珊瑚礁对珊瑚白化现象表现出了顽强的抵抗力,这归因于在索德瓦纳观测到的冷水温度异常。本研究调查了 1994 年至 2015 年间在索德瓦纳发现的 63 个温度异常现象相关的区域水动力过程。研究发现,65%的异常现象与德拉古纳半岛附近的冷水远程上涌有关,随后从德拉古纳湾向索德瓦纳地区平流。上涌的冷水直接从半岛沿大陆架向索德瓦纳平流,或在德拉古湾内再循环,然后沿海岸线向索德瓦纳平流。其余 35% 的异常现象与索德瓦纳以南夸祖鲁-纳塔尔湾内的局部上升流有关。研究还发现,从德拉古阿半岛分离出的强间歇性南向流与德拉古阿半岛的上升流密切相关。然后,上升流的冷水通过区域流动模式平流到索德瓦纳地区,导致索德瓦纳温度异常。当地上升流同样与索德瓦纳附近阿古哈斯海流流速的增加以及夸祖鲁-纳塔尔湾北部海流与海岸线的分离有关。与德拉戈阿半岛附近远程和当地上升流相关的条件平均流场与上升流发生时的瞬时流场之间的交叉相关性表明,21 年来所有异常现象均呈正相关。与远程上升流相关的异常值平均相关系数为 0.67,最大相关系数为 0.96。这项研究表明,东南非海岸线的独特几何形状是导致索德瓦纳冷水温度异常的关键因素。区域水动力与德拉古阿湾和纳塔尔湾等海岸线特征之间的相互作用,对最终导致索德瓦纳冷水温度异常的上升流至关重要。如果没有这些海岸线特征,如果没有该地区的高涡流动能使沿海岸线的南向气流间歇性增强,索德瓦纳很可能就不会出现这些温度异常现象。如果没有这些温度异常现象,索德瓦纳珊瑚礁将更容易受到气候变化和珊瑚白化的影响。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 去求助
来源期刊
Continental Shelf Research
Continental Shelf Research 地学-海洋学
CiteScore
4.30
自引率
4.30%
发文量
136
审稿时长
6.1 months
期刊介绍: Continental Shelf Research publishes articles dealing with the biological, chemical, geological and physical oceanography of the shallow marine environment, from coastal and estuarine waters out to the shelf break. The continental shelf is a critical environment within the land-ocean continuum, and many processes, functions and problems in the continental shelf are driven by terrestrial inputs transported through the rivers and estuaries to the coastal and continental shelf areas. Manuscripts that deal with these topics must make a clear link to the continental shelf. Examples of research areas include: Physical sedimentology and geomorphology Geochemistry of the coastal ocean (inorganic and organic) Marine environment and anthropogenic effects Interaction of physical dynamics with natural and manmade shoreline features Benthic, phytoplankton and zooplankton ecology Coastal water and sediment quality, and ecosystem health Benthic-pelagic coupling (physical and biogeochemical) Interactions between physical dynamics (waves, currents, mixing, etc.) and biogeochemical cycles Estuarine, coastal and shelf sea modelling and process studies.
期刊最新文献
Storms can increase beach resilience on a low-energy coast in the proximity of a harbor The Dnipro-Buh plume: A tale of high-volume freshwater discharge in a non-tidal sea Sedimentation characteristics of surficial sediments in Baiyun Canyon area, Northern South China Sea Analysis of the annual number of tropical cyclones over Japan using the extreme value theory Phosphorus fractions and their vertical distribution in seabed sediments of the eastern Baltic Sea
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
现在去查看 取消
×
提示
确定
0
微信
客服QQ
Book学术公众号 扫码关注我们
反馈
×
意见反馈
请填写您的意见或建议
请填写您的手机或邮箱
已复制链接
已复制链接
快去分享给好友吧!
我知道了
×
扫码分享
扫码分享
Book学术官方微信
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术
文献互助 智能选刊 最新文献 互助须知 联系我们:info@booksci.cn
Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。
Copyright © 2023 Book学术 All rights reserved.
ghs 京公网安备 11010802042870号 京ICP备2023020795号-1