ALBERT

Beschreibung: In West Africa, surface water dynamics of the Senegal river floodplain remain poorly understood by hydrological monitoring and modelling due to data scarcity and the flat, heterogeneous topography. Understanding their variability under anthropic and climate changes are essential to support ecosystem services including flood recession farming, biodiversity and groundwater recharge. Multi-sensor earth observations from Landsat, MODIS and Sentinel-2 are classified and extracted through cloud-computing geoprocessors (Google Earth Engines) to explore surface water dynamics from 1999-2020 over this 2250 km² floodplain, and combined with ground-based observations to derive a statistical model between flooded areas and upstream flow data. The impact of climate change and upstream dam construction on surface water areas are simulated based on a combined GR4J rainfall-runoff and WEAP modelling approach. Results identify large variations in peak flooded areas between 150,000 ha and 450,000 ha (mean 226,800 ha). Strong correlations obtained between monthly maximum flow at Bakel gauging station and annual peak flooded areas (R² = 0.87) allow simulations of future trends. Projections from 7 Cordex RCM models under RCP4.5 and RCP8.5 highlight significant divergences between scenarios, however results concur towards a decline in peak flooded areas (mean 164,000 ha over 2020-2065). WEAP simulations of four planned dams reveal inundated areas may decline under 100,000 ha, but also highlight how dam management including translucent releases would increase flooded areas (〉42%) with minimal impact on hydropower production. Outputs can help design adequate river basin development strategies and optimise water allocation between growing, competing demands in the Senegal river basin.

Beschreibung: Sea level will continue to rise beyond the 22〈sup〉nd〈/sup〉 century due to inertia in the climate system, even if temperatures were immediately stabilised, leading to the proposal of more dramatic measures, such as geoengineering. To provide initial sea level contribution (SLC) estimates from the AIS and address long-term commitment and reversibility questions, a set of idealized geoengineering scenarios were performed with the BISICLES ice sheet model. Climate forcings were extended beyond 2100 to 2200 by either fixing the climate at 2100 (2050) levels at the end (middle) of the century (commitment scenarios), or immediately returning to 2015 levels (e.g. via an instantaneous implementation of geoengineering). Results show that for both high (RCP8.5) and low (RCP2.6) forcing scenarios, reverting back to 2015 climate does not prevent significant loss from the AIS. However, if geoengineering methods are adopted in 2050, SLC is lower than in the commitment scenarios. If geoengineering is implemented in 2100, results are more uncertain but indicate a higher SLC over the 22〈sup〉nd〈/sup〉 century compared with doing nothing, for RCP8.5 scenarios. This is because increased surface mass balance in the RCP8.5 commitment scenarios offsets more of the dynamic losses than in the geoengineered scenarios. While late implementation of geoengineering may therefore actually be more harmful to the ice sheet when compared with the original global warming it aims to counteract, SLC trajectories do slow for these scenarios, hinting at eventual recovery, indicating the potential reversibility of AIS mass loss beyond 2200.