Contributions of rising mean river level of the Río de la Plata estuary on recorded changes in positive storm surges

A 117-year series of hourly-observed heights in the Río de la Plata estuary allows studying the recorded changes in positive storm surge (PSS) events spanning from 1905 to 2021, and calculate the annual mean river level (AMRL) trend. The analysis of PSS focuses on the trend of the annual number of events, the annual mean events duration, and the annual maximum PSS height. Seasonal analyses of these variables can also be conducted. This study aimed to ascertain any correlation between the rising AMRL and the evolution of PSS. Since AMRL increase is related to the effects of global warming, the observation series is divided into two periods based on the behavior of the curve of greenhouse gas emissions into the atmosphere. One period covers 1905 to 1962 and is characterized by a less pronounced curve slope, while the other period, 1965 to 2021, exhibits a drastically steeper curve slope. Moreover, two sets of data were obtained to calculate the PSS in two different scenarios for both periods: a hypothetical one, with no trend in AMRL, and a realistic one, maintaining the observed AMRL trend. The results show the acceleration trend of two of the analyzed variables, namely the annual number of events and the average duration of events, when transitioning from one period to the other (following the behavior observed in AMRL). However, the increase in AMRL could not be the only explanation of these accelerations. On the one hand, although the accelerations decrease when the hypothetical scenario is considered, they do not totally disappear. Moreover, the annual average duration of the events increases follows the realistic scenario when removing AMRL trend. On the other hand, the maximum height of PSS shows no trend in either period and remains unaffected comparing the two scenarios.

Keywords:
Positive storm surges; Sudestadas; Annual mean river level; Climate change; Global warming