Circum Antarctic and East Antarctica
Antarctica and the Southern Ocean play a disproportionately important role in modulating global sea level and Earth’s carbon cycle. Program 1 will focus on the large-scale drivers and small-scale processes that affect ocean and atmosphere circulation which modulate transport of heat and moisture to the Antarctic margin and East Antarctic ice sheet, as well as Southern Ocean productivity and biogeochemical (BCG) cycles. Incorporating outputs from the other programs, Program 1 will improve predictions of how sea level and the carbon cycle will be affected in the future by changes in Antarctica and the Southern Ocean. This will require the integration of historical and new observations for the detection and attribution (D&A) of change, constraints from palaeoclimate data on how and why circulation, mass balance and melt rates can change, process studies to understand the interaction between ocean, atmosphere, ice, solid earth and ecosystems, and a hierarchy of model experiments to understand past change and provide future projections. The program will make connections between modelling and analysis frameworks, and generate data-driven knowledge that informs the risks to the effective prediction of how ice sheets, oceans and climate respond to conditions and changes at, and across, system boundaries. Computer-based data analytics provided in Program 1 will help guide optimal field sampling, enable analysis of under-observed systems in other programs and provide new insight into the complex coupled system.
How can shifts in carbon, heat and moisture transport in the Antarctic and Southern Ocean system be better constrained to improve projections of future climate and sea level changes?
Quantify the biological carbon pump (productivity) in the Southern Ocean (SO) and assess drivers of its recent (~20 years) variability and how productivity may change in the coming decades in response to changes in the physical environment (natural and climate change driven):
- Use historical satellite records (ocean colour, temperature, altimetry, wind), BGC-Argo and other field observations to identify temporal signals in the phytoplankton ecosystems and their physical drivers from seasons to decadal timescales.
- Assess the forcing role of the physical environment on the carbon pump from the meso-scale (eddies) to the basin-scale, and from seasonal to decadal time scales.
- Combine the above with the 3D SO-scale modelling to improve projections of the efficiency of the biological carbon pump. Contribute to improving the modelling of the biological pump in that frame.
- Use observations (optics and BGC) from past and upcoming field efforts to understand why the Southern Ocean still poses an issue to satellite ocean colour (with a view to improving algorithms).
Quantify the changes to and the understand drivers of ocean and atmospheric circulation across a range of timescales affecting the flow of heat and moisture to the eastern Antarctic system:
- Understand changes to the atmospheric circulation (including heat and moisture fluxes) across timescales associated with anthropogenic forcing, regional and remote variability.
- Determine how circulation changes/climate modes and other local processes affect ocean circulation at the Antarctic margin.
- Quantify oceanic heat and other tracer fluxes to the Antarctic margin.
- Understand how increased melt rates will feed back to the large scale circulation.
Determine how East Antarctica affects sea level across a range of past and future timescales:
- Use geophysical data (heat flux, sub-ice meltwater, basal sediments, vertical land motion) to constrain where the solid Earth may affect ice sheet stability in parts of East Antarctica, and improve solid Earth models (Glacial Isostatic Adjustment [GIA]/viscosity) to provide a better constraint on future sea level rise projections
- Improve the quantification of ocean warming driven ice shelf/sheet loss from coastal East Antarctica through improved incorporation of high resolution processes at the ice sheet margin into Earth system models.
- Improve the spatial and temporal understanding of past surface accumulation variability and trends across the surface of parts of the East Antarctic ice sheet and the potential role of surface accumulation in offsetting ice loss at the ice sheet margin.
- Combine improved regionals projections for East Antarctic ice mass change into global sea level projections.
- Assess risks to the effective prediction of changes to ice mass, ocean and climate, that arise from interactions and feedbacks between systems, across boundary domains, variability, and instability/threshold changes
Improve the detection of variability and trends in the Southern Ocean and Antarctic climate, and their attribution to natural and/or anthropogenic climate processes:
- Assess regional characteristics and temporal trends and variability in satellite altimeter and tide gauge datasets.
- Improve the resolution and accuracy of satellite-derived estimates of surface mass balance over East Antarctica, including improving models of firn compaction and assessment of satellite datasets alongside ice-core derived histories of snow accumulation.
- Improve the measurement of meltwater input from coastal East Antarctica
- Assess reconstructions, observations and model simulations for East Antarctic and Southern Ocean change within the CMIP D&A framework.
Alex Sen Gupta