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|Present-Day Sea-Level Change Along The South American Atlantic Coastline From Tide Gauges And Satellite Altimetry Data (1993-2019)|
Andrawina, Y (2021). Present-Day Sea-Level Change Along The South American Atlantic Coastline From Tide Gauges And Satellite Altimetry Data (1993-2019)
. MSc Thesis. NIOZ Royal Netherlands Institute for Sea Research: Yerseke. 60 pp.
Sea-level change (SLC) is one of the most recognizable climate change indicators. The knowledge of the present-day SLC is pivotal for constraining future sea-level projections and preparing the adaptation in coastal communities. However, the change in sea level is not a smooth and globally uniform process, it presents regional variations that could be associated with vertical land motion, surface warming and cooling of the ocean, exchange of freshwater with the atmosphere and land through evaporation, precipitation, and runoff, and surface wind stress. Generally, the sea-level observation systems are composed of tide gauges and satellite altimetry. Nonetheless, estimating coastal SLC using altimetry data is challenging due to the distortion of the satellite signal close to the land. However, recent studies have been dedicated to the evaluation and improvement of altimetry corrections in coastal areas. While such studies have focused mainly on the Northern Hemisphere, where the in-situ measurement have a large spatial and temporal resolution, a new network of tide gauges deployed along the coast of Brazil (by the SIMCosta project) made it possible to validate the altimetry sea-level anomalies (SLA). Aiming to compensate the lack of study in the Southern Hemisphere, this research estimated SLA trend using altimetry data from X-TRACK-AVISO, which could retrieve the reliable altimetry data up to 10 km near the coastline. The validation with the 10 tide gauges dataset showed that the X-TRACK data can be used to detect the SLA along the South American Atlantic coastline, with an average correlation value nearly more than 0.4 Pearson(r) and the RMSD lower than 1. For estimating the sea-level trend, two statistical approaches were used, an Ordinary Least Square (OLS) and the non-parametric statistical seasonal Mann Kendall (MK). Both methods indicate a reliable SLA trend, with similar values. The average SLA trend over the South American Atlantic coastline is 3.80 ±1.20 mm/year ( 95% confidence interval uncertainty), similarly to the GMSL rate (3.20 ± 0.05 mm/year from 1993-2015; Oppenheimer & Glavovic, 2019). Regionally, the SLA trends varied between about -1.44 to nearly 8.06 (± 0.50 to 3.00) mm/year along the South American Atlantic coastline. The lowest rate was found in the coastal area near the Puerto Deseado (Argentina), with a value of -1.44 ± 1.89 mm/year. The highest increasing sea-level trend, with more than 5.00 ± 1.50 mm/year, was found mainly near the Amazon and La Plata estuaries and near the Brazil-Malvinas Confluence Zone.