Enhancing New Zealand’s Earth system modelling capability through ice-sheet coupling
The effect of melting polar ice sheets on our environment and ecosystems remains uncertain - can the coupling of ice sheet and climate models be improved to make more robust predictions for the future? Dr Alanna Alevropoulos-Borrill aims to find out in this Opportunity Fund project.
Background
The polar ice sheets are melting at accelerating rates as the Earth’s climate changes. The largest uncertainty in projecting future sea level rise is the contribution of the melting Antarctic Ice Sheet. This ice sheet knowledge is also critical to determine the effects of change on our environment and ecosystems.
Computer based numerical models, which mathematically represent components of the Earth system, can simulate the evolution of both climate and ice sheets in response to increased anthropogenic emissions. Current ice sheet model projections of future Antarctic Ice Sheet evolution mostly consider ice sheet surface changes, which are driven by atmosphere and ocean forcing. In reality, continental scale ice sheets are interactive components of the Earth System, which evolve simultaneously alongside the climate and transform the local atmosphere and ocean, which they are also influenced by.
Working with local researchers and overseas collaborators, this project aims to overcome the limitation of running stand-alone models of ice, ocean and atmosphere. Accounting for the synchronous evolution of both the climate and the Antarctic Ice Sheet within Earth System Models (ESM) will drastically improve the physical representation of observed ice sheet and climate processes and reduce uncertainty in sea level rise estimates.
Research overview
This research aims better quantify how the Antarctic Ice Sheet will interact with the ocean and atmosphere as it responds to a warming climate. We will couple the BISICLES (Berkeley Ice Sheet Initiative for Climate at Extreme Scales) ice sheet model and the New Zealand Earth System Model (NZESM).
NZESM is made up of constitutive models to represent each component of the earth system: the atmosphere, ocean, sea ice and dynamic land. The ocean is simulated by the model NEMO (“Nucleus for European Modelling of the Ocean”) and sea ice is modelled by CICE. The United Kingdom Hadley Centre’s Unified Model (UM) is included for the simulation of the global atmosphere with JULES (Joint UK Land Environment Simulator) to represent the dynamic land surface. NZESM also includes representation of evolving biogeochemistry within the ocean, modelled with MEDUSA (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification) and includes the chemistry of the atmosphere.
As the ice sheet interacts directly with the atmosphere, ocean and land surface, model coupling allows each of these components to communicate. A working framework of the coupling procedure exists, which will allow our project to make rapid progress despite what is internationally recognised as a challenging and complex task.
Our two primary goals are to:
- establish a functioning, fully-coupled BISICLES-NZESM model framework running on the New Zealand e-Science Infrastructure (NeSI) supercomputer, Māui, and
- use this coupled model to perform future simulations exploring Antarctic Ice Sheet evolution, and the ice-ocean-atmosphere feedbacks that might arise.
This will be the first and only fully coupled Earth System Model with an interactive ice sheet available to use in New Zealand. The incorporation of an interactive ice sheet will present new projections for the future evolution of Antarctica and improve the representation of Earth System processes that are influenced by changes over the ice sheet.
Collaborators
- Nicholas Golledge (VUW, NZ) - developing and refining model simulations
- Jonny Williams (NIWA, NZ) - NZESM development
- Dan Lowry (GNS Science, NZ) - experimental design and interpretation of results
- Stefan Jendersie (VUW, NZ) - developing the sub-ice shelf melt modifications required in NZESM-ice
- Robin Smith (National Centre for Atmospheric Science, UK) - coupling work that integrates BISICLES
- Dan Martin (Lawrence Berkeley National Laboratory, USA) -ice sheet model development and ice-ocean model coupling; BISICLES
- Stephen Cornford (University of Bristol, UK) - ice sheet model development; BISICLES
- Antony Payne (University of Bristol, UK) - use of ice and climate models to make scenario-based projections
- Claire Donnelly (Royal Dutch Meteorological Institute, KNMI, The Netherlands) – model comparison; currently coupling BISICLES with EC-EARTH at KNMI with a focus on Antarctica
Nansen Ice Shelf is 48km long and 16km wide, located along the coast of Victoria Land, Antarctica. Photo: Craig Stevens