Long-Term Trends and Variability of Water Levels and Tides in Buenos Aires and Mar del Plata, Argentina

Sara Santamaria-Aguilar,Athanasios T Vafeidis,Silvina C Carretero,Mark Schuerch

doi:10.3389/fmars.2017.00380

Abstract

We present an analysis of the long-term trends and variability of extreme water and tidal levels and the main tidal constituents using long-term records from two tide gauges in the wider region of the Rio de la Plata estuary: Buenos Aires (1905–2013) and Mar del Plata (1956–2013). We find significant long-term trends in both tidal levels and the main tidal constituents (M2, S2, K1, O1, and the overtide M4) from a running harmonic analysis in both locations. The tidal range decreased on average 0.63 mm y−1, as a result of an increase of the low water levels and a decrease of the high water levels. We also find a secular decrease in the amplitude of the semi-diurnal constituents and an increase of the diurnal ones, but of different magnitudes at each location, which suggests that different processes are producing these changes. In Buenos Aires, an increase of river discharge into the estuary seems to reduce the tidal range by hampering the propagation of the tidal wave into the estuary, whereas no influence of river discharge on water and tidal levels can be detected in Mar del Plata. We believe that other factors such as thermohaline changes or the rise of mean sea-level may be responsible for the observed tidal range decrease. Despite the tidal long-term trends, we find no significant trends in the meteorological component of the tide-gauge records other than an increase in the mean sea-level. In addition, we explore teleconnections between the variability of the meteorological component of the tide-gauge records and climate drivers.

Highlights

Determination of trends and variability of extreme water levels (WLs) is complex due to their high natural variability arising from the nature of extreme WLs components: mean sea level (MSL), tide and surge
Our analysis shows that low WLs have risen faster than MSL over the last century in Buenos Aires and the last 40 years in Mar del Plata
We observe a decrease of the tidal ranges (MTR, greater diurnal tidal range (GDTR), and lesser diurnal tidal range (LDTR)) of 0.5 mm y−1 on average that arises from a decrease of the amplitude of the semidiurnal constituents and an increase of the diurnal constituents, as well as changes in the phases

Summary

Introduction

Determination of trends and variability of extreme water levels (WLs) is complex due to their high natural variability arising from the nature of extreme WLs components: mean sea level (MSL), tide and surge. Knowledge of past long-term trends and inter-annual variability of extreme WLs as well as the drivers of these changes is required in order to reduce uncertainty when modeling the frequency and magnitude of future extreme WLs (Wahl and Chambers, 2015, 2016), because the uncertainties related to future trends and variability of WLs caused by climate change (e.g., sea-level rise, changes in storminess) are high (Wahl et al, 2017). In most areas of the world, secular changes in extreme WLs over the last century have been found to be of similar magnitude. A better understanding of the links between atmospheric dynamics and extreme WLs variability is needed in order to better model their occurrence probability (see e.g., Cid et al, 2015)

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