Jonathan Barnsley

Earth, Atmosphere and Ocean Processes

KCL

UCL

Lauren Gregoire (University of Leeds),

Sea level rise represents an existential threat to coastal populations and ecosystems. The response of the Antarctic ice sheet to climate change is the highest uncertainty in future sea level projections. The primary vehicle for studying these uncertainties is through the use of ice sheet models to simulate ice sheet evolution under different emission scenarios. However, the majority of modelling efforts to date have focused on end of the century projections. Models that have run multi-millennial simulations of the Antarctic ice sheet all either compromise on model complexity or use a grid resolution that is too coarse to robustly model grounding line retreat.

This project will conduct millennial-scale simulations of future Antarctic ice sheet evolution using the BISICLES ice sheet model, which uses Adaptive Mesh Refinement to improve resolution at the grounding line. Until recently, BISICLES was incapable of conducting multi-millennial simulations due to lacking the solid Earth processes that become relevant on these timescales. This project will expand on previous work, which added these processes to BISICLES and used it to simulate Antarctic ice sheet evolution during the Mid-Pliocene Warm Period. It will use information from the Pliocene to put constraints on future sea level rise. It will then emulate BISICLES using a statistical model to explore the uncertainties in future sea level projections in more depth, producing full probability distributions for sea level by 2300 and after multiple millennia.

The IPCC Sixth Assessment Report identified sea level rise as ‘an existential threat for some Small Islands and some low-lying coasts’. Even a sea level rise of 1m would increase the global population exposed to coastal flood risk from 267 million at present to at least 410 million (Hooijer & Vernimmen, 2021), with this figure dominated by lowlands in tropical Asia such as the Ganges delta. Scenario modelling of different emission pathways, with sea level rises of 30-86 cm by 2100, show that a reduction in greenhouse gas emissions over this century could save trillions of dollars of global assets from falling within a 100-year floodplain (Hinkel et al., 2014). Coastal ecosystems, which provide ecosystem goods and services to local populations, have been shown to be sensitive to rapid sea level rise, with complex impacts – both positive and negative – varying by species (e.g. Albert et al., 2017). Projecting and adapting to sea level rise is therefore of great interest to policymakers looking to preserve biodiversity, safeguard economic assets, and protect vulnerable populations.

• Chris Brierley, Kaustubh Thirumalai, Edward Grindrod, and Jonathan Barnsley (2023) Indian Ocean variability changes in the Palaeoclimate Model Intercomparison Project Climate of the Past DOI: https://doi.org/10.5194/egusphere-2022-1102