High waters at Liverpool since 1768: The UK's longest sea level record

Abstract

An exercise of 'data archaeology' of high water tidal information from Liverpool, NW England has resulted in the construction of a time series of 'Adjusted Mean High Water' spanning 1768 to the present which can be employed as a record of proxy Mean Sea Level (MSL). The time series, although gappy, is arguably the second oldest sea level-related record in the world, after Amsterdam's (1682, although the data we hold are from 1700 only) and of comparable age to Stockholm's (1774). It describes a secular trend for the period up to 1880 of 0.39 +/-0.17 mm/year, a trend for the twentieth century of 1.22 +/-0.25 mm/year, and an overall low frequency acceleration of 0.33 +/- 0.10 mm/year/century. When considered alongside geological sea level information from the area, the evidence suggests that the greater secular trend of sea level in the twentieth century, compared to long term projections derived from geological information, is primarily the result of an acceleration towards the second half of the last century, consistent with conclusions inferred from previous analyses of the very small number of other long European MSL records.