Vertical ground motion and historical sea-level records in Dakar (Senegal). (17th August 2015)

• Record Type: Journal Article
• Authors: Le Cozannet, Gonéri; Raucoules, Daniel; Wöppelmann, Guy; Garcin, Manuel; Da Sylva, Sylvestre; Meyssignac, Benoit; Gravelle, Médéric; Lavigne, Franck
• Is Part Of: Environmental research letters. Volume 10:Number 8(2015:Aug.)
• Publication Date: 2015-08-17
• Subjects: sea-level rise -- tide gauges -- vertical ground motions -- geodetic instruments -- Dakar -- African coasts; Environmental sciences -- Periodicals; Human ecology -- Research -- Periodicals; Environmental health -- Periodicals; 333.7
• DOI: 10.1088/1748-9326/10/8/084016
• Languages: English
• ISSNs: 1748-9326

Abstract

Abstract: With growing concerns regarding future impacts of sea-level in major coastal cities, the most accurate information is required regarding local sea-level changes with respect to the coast. Besides global and regional sea-level changes, local coastal vertical ground motions can substantially contribute to local changes in sea-level. In some cases, such ground motions can also limit the usefulness of tide-gauge records, which are a unique source of information to evaluate global sea-level changes before the altimetry era. Using satellite synthetic aperture radar interferometry, this study aims at characterizing vertical coastal ground motion in Dakar (Senegal), where a unique century-long record in Africa has been rediscovered. Given the limited number of available images, we use a stacking procedure to compute ground motion velocities in the line of sight over 1992–2010. Despite a complex geology and a rapid population growth and development, we show that the city as a whole is unaffected by differential ground motions larger than 1 mm year −1 . Only the northern part of the harbor displays subsidence patterns after 2000, probably as a consequence of land reclamation works. However, these ground motions do not affect the historical tide gauge. Our results highlight the value of the historical sea-level records of Dakar, which cover a 100 year time-span in a tropical oceanic region of Africa, where little data are available for past sea-level reconstructions.