River effects on sea-level rise in the Rio de la Plata estuary during the past century

Identifying the causes for historical sea-level changes in coastal tide-gauge records is important for constraining oceanographic, geologic, and climatic processes. The Rio de la Plata estuary in South America features the longest tide-gauge records in the South Atlantic. Despite the relevance of these data for large-scale circulation and climate studies, the mechanisms underlying relative sea-level changes in this region during the past century have not been firmly established. I study annual data from tide gauges in the Rio de la Plata and stream gauges along the Rio Paran & aacute; and Rio Uruguay to establish relationships between river stream flow and sea level over 1931-2014. Regression analysis suggests that streamflow explains 59 % +/- 17 % of the total sea level variance at Buenos Aires, Argentina, and 28 % +/- 21 % at Montevideo, Uruguay (95 % confidence intervals). A longterm streamflow increase effected sea-level trends of 0.71 +/- 0.35 mm yr(-1) at Buenos Aires and 0.48 +/- 0.38 mm yr(-1) at Montevideo. More generally, sea level at Buenos Aires and Montevideo respectively rises by (7.3 +/- 1.8) x 10-6 m and (4.7 +/- 2.6)x10(-6) m per 1 m(3) s(-1) streamflow increase. These observational results are consistent with simple theories for the coastal sea-level response to streamflow forcing, suggesting a causal relationship between streamflow and sea level mediated by ocean dynamics. Findings advance understanding of local, regional, and global sea-level changes; clarify sea-level physics; inform future projections of coastal sea level and the interpretation of satellite data and proxy reconstructions; and highlight future research directions. Specifically, local and regional river effects should be accounted for in basin-scale and global mean sea-level budgets as well as reconstructions based on sparse tide-gauge records.

Automated summary

This study analyzes tide gauge and stream gauge data in the Rio de la Plata estuary to establish the relationship between river stream flow and sea level changes. The results show that streamflow explains a significant portion of sea level variability at Buenos Aires and Montevideo. The findings highlight the causal relationship between streamflow and sea level, advancing our understanding of local, regional, and global sea-level changes.