A century-long simulation of terrestrial water storage change and its contribution to global sea-level

Abstract:

Although limited, the contribution of terrestrial water storage (TWS) change to sea-level change is significant enough to be taken into account in sea-level attribution studies. Thus, after being absent in a previous report, TWS was again one of the components taken into account in IPCC assessment report 5. TWS can be effectively observed by analysing gravity anomalies from the GRACE mission or by observing individual components with lidar (surface water level), geodetic surveys (groundwater) and space borne passive and active microwave sensors (soil moisture, snow water equivalent). However, these observation only yield time series of limited length making it difficult to estimate long term trends in TWS as multi-decadal variations. After a short review of recent modelling efforts, we present the results of a century-long (1900-2010) simulation of TWS change with PCR-GLOBWB 2.0 that is fully coupled with a global two-layer groundwater model. In this simulation we include the effects of land cover change, the building of reservoirs and human water use (abstraction from surface and groundwater, water consumption and return flows). The effects of wetland drainage and siltation of reservoirs is corrected for afterwards. We validate TWS estimates for the period 2003-2010 with GRACE estimates. Trends of TWS and its effects on sea-level change are estimated and the main contributions identified. Similarly, we examine multi-year variability in TWS and sea-level change in relation to climate variability.