Monthly sea level peak for March 2021

The lunar month’s highest tide occurred between 27th March and 1st April 2021 for Waitemata harbour and Great Barrier Island.

The Waitemata harbour tidal gauge measured a mean level of 1.73 metres between 10:15am and 10:30am on 31st March which is 8cm above the March average (2015-2020). The barometric air pressure at the time of the reading was 1007.8 hPa, so when using the inverted barometric adjustment calculation method of 1cm for every 1 hPa, the projected height would have been 1.68 metres at the mean sea level pressure of 1013 hPa. More on meteorological effects on tides can be found here.

The ongoing trend between 2014 to 2021 for the Waitemata harbour sea level peak is downward. The tidal gauge data used for this analysis can be found here.



The Great Barrier Island tidal gauge measured a mean level of 1.18 metres between 09:30am and 09:45am on 31st March. The air pressure at the time of the reading was 1009.4 hPa, so when using the inverted barometric adjustment calculation method of 1cm for every 1 hPa, the projected height would have been 1.14 metres at the mean sea level pressure of 1013 hPa. More on meteorological effects on tides can be found here.

Note# A non tidal 30cm tsunami event occurred on 5 March from an M 8.1 earthquake on the Kermadec trench reaching to 1.25 metres mean sea level. This is not included in the data and graph due to the non tidal nature of the peak.

The ongoing trend between 2014 to 2021 for Great Barrier Island sea level peak is a flat trend. The tidal gauge data used for this analysis can be found here.




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