CoAuthors

Jürgen Kusche (University of Bonn, Institute of Geodesy and Geoinformation, Germany); Roelof Rietbroek (University of Bonn, Institute of Geodesy and Geoinformation, Germany); C K Shum (Ohio State University, Division of Geodetic Science, School of Earth Sciences, USA)

Today, sea level rise and its likely acceleration represents a major global challenge, affecting numerous countries. Total sea level rise results from various sources, such as mass changes from melting of glaciers/ice caps and the Greenland and Antarctica ice-sheets, influences from terrestrial hydrology, glacial isostatic adjustment, as well as volumetric (steric) changes caused by temperature and salinity variations; each of which does not simply result in a uniform layer of sea level rise, but exhibits a distinct spatial pattern. Identifying the dominant contributions of these sources at regional scale is required for improved understanding of sea level rise and eventually enabling more accurate predictions.

In a joint inversion method, normalized spatial patterns (fingerprints) are forward-computed for each of the contributors, consistent with the sea level equation for mass fingerprints, e.g. individual ice-sheets and glaciers and the dominant modes of steric sea level fingerprints derived from ARGO float data. Complementary temporal GRACE gravity data and along-track Jason-1 and -2 altimetry data are then combined to estimate the time variable amplitudes of these individual fingerprints, which allow the computation of regional sea level trends linked to each of the considered contributors.

In this work, we assess results from our global inversion for the Bay of Bengal region using additional regional data sets within the framework of the of the Belmont-project "Bangladesh Delta: Assessment of the Causes of Sea-level Rise Hazards and Integrated Development of Predictive Modeling Towards Mitigation and Adaptation" (BanD-AID). In Bangladesh, large areas of the country lie just above the sea level. Here, sea level rise in combination with land subsidence resulting from groundwater pumping, sediment load and/or tectonic motion, poses a major threat to the coastal regions, which are the home of about 30 million inhabitants. Estimated sea level trends are compared to trends derived from tide gauge data, as well as altimetry and their differences are interpreted in terms of unmodeled regional effects, such as land subsidence or seasonal influences. The initial results of the inversion provide an indication on the magnitude of the contributions from the different sources at the coast of Bangladesh; e.g. the contribution from the Greenland ice-sheet between 2003 and 2011 (0.69 mm/yr) is significantly larger compared to the contribution from Antarctic ice-sheet (0.15 mm/yr), but the largest effect results from highly variable steric sea level changes in the Bay of Bengal (-1.5 to 6 mm/yr).