PROGRAM 3

Sub-regional and Regional Antarctic Margins

Program 3 will focus on understanding the response of the icesheet/climate system to climate change, for areas understood to be vulnerable to rapid deglaciation of the ice sheet. The Program will focus on the integration of studies that cover the spatial domains from ice sheet accumulation basins through to the continental shelf break over a range of timescales. We will use existing datasets and modelling to examine processes within these time and space scales and build towards a field program with a specific focus on the Denman/Shackleton region.

What is the risk of ice mass loss from key subglacial basins over the next decades to centuries, and what are the consequences for the local oceans and ecosystems?

Quantify recent historical drivers and rates of retreat for key subglacial basins, with a key focus on the Denman Glacier region:

    1. Quantify mass inputs: Recent accumulation history and processes at the basin scale with reanalysis products.
    2. Quantify mass outputs: Basal melt coupled with measurements and modelling of ocean circulation pathways and variability within the cavity and upstream on the continental shelf.
    3. Examine retreat processes and feedbacks: bedrock uplift rates, glacier sliding and linkages with subglacial hydrology, geothermal heat flow and sedimentation for grounding line wedge stabilization, local atmospheric and oceanic forcing.

Quantify the stability of susceptible basins/glaciers and the risk of passing tipping points:

    1. Use a coupled model to explore ice retreat processes in the region and examine the sensitivity to climate.
    2. Obtain high-resolution geometry of continental shelf, subglacial basins, sub ice shelf ocean cavities and grounding zone conditions to constrain the models using a range of activities including geological mapping, and airborne and ship-based geophysics.
    3. Separate the signal caused by a warming climate from decadal variability in the historic record.
    4. Use coupled models to determine when/if ice retreat is likely to cross a tipping point, and how this region compares to EA generally.

Use palaeo reconstructions to provide an integrated view of possible futures for susceptible basins:

    1. Use marine sediment cores recovered from the slope to reconstruct ice sheet state for past climates warmer than present. This approach uses the analysis of new and legacy detrital sediment records coupled to knowledge of subglacial geology and sediment transport modes.
    2. Determine historical ice sheet volumes and retreat rates through bathymetric mapping, offshore geophysical data and land-based approaches (e.g. 10Be exposure dating).
    3. Compare modelled estimates of the timing, sequencing and magnitude of past basin-scale ice sheet retreat with observational constraints and thereby select the best model.
    4. Use an ice sheet model to understanding source to sink sediment pathways - useful for both understanding the hidden under ice geology, and also planning future fieldwork effort.

Identify how past and projected ice melt for key basins can impact local ecosystems in the adjacent ocean and seafloor through altered ocean state, iron fertilisation and sea ice (cross-program outputs):

    1. Quantify the iron supply associated with the retreating ice sheet including melt water and subglacial hydrology. This will involve sampling the ice sheet and melt water. Quantify meltwater input and its iron content. May include measurements of iron speciation, and measurements of ice sheet tracers other than salinity (e.g. d18O, uranium isotopes, noble gasses through collaborations).
    2. Collect remote and in-situ observations to evaluate the influence of interannual variability in ice shelf melting and subglacial discharge events on primary productivity and seafloor biodiversity.
    3. Apply a regional model including BGC with glacial iron supply to predict regional ecosystem impacts. Can link to broader scale models to explore impacts on MIZ ecosystems of ice sheet iron.
    4. Use palaeoceanographic records to reconstruct ocean productivity and iron supply during past episodes of ice sheet retreat, as a way of assessing the integrated response and to evaluate models.

 

Ben G-F

Ben Galton-Fenzi

AAD

Zanna Chase

Zanna Chase

UTas

Adele Morrison

Adele Morrison

ANU