Preprints
https://doi.org/10.5194/egusphere-2023-2997
https://doi.org/10.5194/egusphere-2023-2997
02 Jan 2024
 | 02 Jan 2024

Could old tide gauges help estimate past atmospheric variability?

Paul Platzer, Pierre Tandeo, Pierre Ailliot, and Bertrand Chapron

Abstract. The storm surge is the non-tidal component of coastal sea-level. It responds to the atmosphere both through the direct effect of atmospheric pressure on the sea-surface, and through Ekman transport induced by wind-stress. Tide gauges have been used to measure the sea-level in coastal cities for centuries, with many records dating back to the 19th-century or even further, at times when direct pressure observations were scarce. Therefore, these old tide gauge records may be used as indirect observations of sub-seasonal atmospheric variability, complementary to other sensors such as barometers. To investigate this claim, the present work relies on tide gauge records of Brest and Saint-Nazaire, two portal cities in western France, and on the members of NOAA's 20th-century reanalysis (20CRv3) which only assimilates surface pressure observations and uses numerical weather prediction model. Using simple statistical relationships between storm surges and pressure maps, we show that the tide gauge records reveal part of the 19th-century atmospheric variability that was uncaught by the pressure-observations-based reanalysis. In particular, weighing the 80 reanalysis members based on tide gauge observations indicates that a large number of members are very unlikely, which induces corrections of several tens of Hectopascals in the Bay of Biscay. These findings support the use of early tide gauge records in sensor-scarce areas, both to validate old atmospheric reanalyses and to better probe old atmospheric sub-seasonal variability.

Paul Platzer, Pierre Tandeo, Pierre Ailliot, and Bertrand Chapron

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2997', Anonymous Referee #1, 29 Jan 2024
  • RC2: 'Comment on egusphere-2023-2997', Anonymous Referee #2, 07 Feb 2024
Paul Platzer, Pierre Tandeo, Pierre Ailliot, and Bertrand Chapron
Paul Platzer, Pierre Tandeo, Pierre Ailliot, and Bertrand Chapron

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Short summary
Old observations are necessary to understand the atmosphere. When direct observations are not available, one can use indirect observations such as tide gauges, which measure the sea-level in portal cities. The sea level rises when local air pressure decreases, and when wind pushes water towards the coast. Several centuries-long tide gauge records are available. We show that these can be complementary to direct pressure observations for studying storms and anticyclones in the 19th century.