Select a start year and end year from the date slider below to see a chart of annual Mean Sea Level (MSL) and it's associated annual rate of change. If a end year in the future is selected, i.e. beyond which there is available observed data, then a linear (black line) and polynomial (purple line) trendline will each show an estimate of MSL from the year which observed data ends up to the year selected by the user.
The mean annual rate of Relative Sea Level (RSL) change for Lyttelton between and is approximately mm per year with a Standard Error of +/- mm per year.
Corrected for subsidence and Vertical Land Movement (VLM) of +/- mm per year (GPS Solution: NGL14), the mean annual rate of Absolute Sea Level (ASL) change for Lyttelton between and is approximately mm per year () with a Standard Error of +/- mm per year.
The mean Relative Sea Level acceleration for Lyttelton between and is approximately mm/year2.
The dark blue line in the above chart is the annual observed Relative MSL for the selected period. This is given as a height above the 1969 tide gauge zero. The intersecting black line is the linear trendline for the selected period. It's gradient is the average annual rate of MSL change who's equation is shown in the legend at the top of the chart. The intersecting purple line is the corresponding quadratic or second degree polynomial trendline who's equation is also shown in the legend at the top of the chart. Hover over each trendline's equation to see it's coefficient of determination R2 value in the tooltip.
The light blue line is the 1986-2005 IPCC Baseline which is the average mean sea level at Lyttelton for the period 1986-2005 and is 1059 mm above above the 1969 tide gauge zero. This baseline is used by the IPCC as a zero for projections and is also used by the NZ government and councils for planning and decision making.
The green, blue, yellow and red lines which begin in 2020 and end in 2050 are the four Representative Concentration Pathway (RCP) sea level rise scenarios for NZ. Namely NZ RCP2.6 M, NZ RCP4.5 M, NZ RCP8.5 M and NZ RCP8.5 H. These scenarios are sourced from table 10 of the Coastal Hazards and Climate Change Guidance for Local Government document published by the Ministry for the Environment and have been converted to heights above the 1969 tide gauge zero by adding 1059 mm.
Hover above any of the lines to see individual annual MSL values in the tooltip. The tooltips for the annual observed Relative MSL (dark blue) line will also show values corresponding to +/- one standard deviation given alongside in brackets.
Please note that Mean Sea Level predicted from the facility to project the above trendlines into the future are estimates only.
I've created an R Shiny app which fits various degree (1-4) polynomials to the above data and also produces p-Values, R-Squared, F-Statistic and t-statistic error parameters which you can find in the navigation menu at the top of this page.
Data for 1901-2012 comes from the work of Paul H. Denys, R. John Beavan, John Hannah, Chris F. Pearson, Neville Palmer, Mike Denham, Sigrun Hreinsdottir and retrieved from URL https://doi.org/10.1029/2019JB018055 "Sea Level Rise in New Zealand: The Effect of Vertical Land Motion on Century-Long Tide Gauge Records in a Tectonically Active Region." January 2020.
Data for 2013-2019 is from Caldwell, P. C., M. A. Merrifield, P. R. Thompson (2015), Sea level measured by tide gauges from global oceans - the Joint Archive for Sea Level holdings (NCEI Accession 0019568), Version 5.5, NOAA National Centers for Environmental Information, Dataset, doi:10.7289/V5V40S7W and downloaded April 2021 from the University of Hawaii Sea Level Center.
Data for 2020-2021 downloaded from Lyttelton Port Company.
Above 2013-2021 data processed by Sea Level NZ using the University of Hawaii Sea Level Center SLP64 software. The SLP64 software uses a 119-point convolution filter to obtain daily MSL values. A simple average of all daily values is calculated if 7 or fewer days are missing to give monthly values and a simple average of monthly values is calculated to give annual values.