Constraints on Long-Period Sea Level Variations from Global Tide Gauge Data

Abstract

We use monthly, global tide gauge data archived at the Permanent Service for Mean Sea Level to search for: (1) the 18.6-year ocean tide; (2) the 14-month pole tide in the deep ocean and in the North Sea region; (3) the response of the ocean to variations in atmospheric pressure; (4) the global rise in sea level; and (5) vertical crustal motions due to post glacial rebound. We typically use data from all of the tide gauges in an individual analysis, employing techniques such as data stacking and least-squares-fitting in time and space. We conclude: (a) the 18.6-year tide and 14-month pole tide in the deep ocean are consistent with equilibrium values to within 20–30%; (b) it is possible that the apparently anomalous pole tide in the North Sea region could, instead, be a response to meteorological forcing of some kind; (c) the response of the deep ocean to variations in atmospheric pressure at periods between 2 months and several decades is consistent with the inverted barometer assumption to within about 5%; (d) the global rise in sea level over the last century has been between 1.45 and 2.60 mm/yr, with a preferred value of 1.75 mm/yr; (e) Peltier’s (1986) model for the vertical uplift caused by post glacial rebound is, in general, in good agreement with the global tide gauge data. Our results suggest the tide gauge data could be useful to help refine post glacial rebound models in the future.