Progress in reconstructing long term global sea level changes
Event: 2016 Ocean Surface Topography Science Team Meeting
Session: OSTST Opening Plenary Session
Presentation type: Type Keynote/invited
Estimates of global sea level change prior to the satellite altimetry era rely on a historical tide gauge data set with limited spatial and temporal sampling. Tide gauges, as pointwise observations, measure local sea level changes resulting from ocean dynamics as well as geoid changes due to mass load redistribution. Since they are grounded on land, tide gauges are also affected by vertical land motion (VLM) of the Earth’s crust that, over decadal and longer time scales, may have amplitudes comparable to climatic signals. The correction of these VLMs represents a challenge in geodesy and is a key factor to understand and quantify past sea level changes. The use of continuous Global Position System (GPS) has revealed an effective approach to measure VLM to the required accuracy. Likewise, the combination of satellite altimetry and tide gauges is useful in determining VLM under the premise that both systems measure the same oceanic signal and instrumental drifts can be neglected. The set of different possible corrections to tide gauge records accounting for different geophysical and oceanographic effects, together with the choice of methodological approaches and data subsets, has led to the development of several global sea level reconstructions with a range of global sea level rise between 1.3 and 2 mm/yr over the past century. Here we explore the impact that the different corrections have on the reconstructed global sea level and propose a new methodology accounting for VLM, ocean volume redistribution and mass load changes.