Highlights from Antarctic ice dynamics research 2021/22

The Project team completed a highly successful 2021/22 Antarctic field season, and produced exciting advances in Antarctic ice dynamics research.

Various field events were deployed to Antarctica for ice shelf drilling and sub-ice shelf evaluation, oceanographic and geophysical survey campaigns.

Our multi-institutional field team undertook successful hot water drilling (KIS-2) through 500m of ice to access a subglacial meltwater channel upstream of the Kamb Ice Stream grounding line, near Siple Dome and deployed sensors in the water column providing real-time data. The spectacular subglacial channel is narrow, less than 200 metres wide, yet the field team was able to pinpoint the optimal drilling site with remarkable accuracy, thanks to a combination of satellite remote sensing and geophysical field site characterisation in prior seasons. We collected a wealth of new biological, geological and oceanographic data from this sub-iceshelf ‘estuary system’.

Several sediment cores were recovered and contain features that have not previously been observed in a sub-ice shelf setting, including a series of graded sand and gravel beds that suggest episodic ‘floods’ flow down the Kamb meltwater channel.

An all-women team deployed four GPS stations on the Ross ice shelf to provide observations of vertical and horizontal deformation (flow changes) that can be related to the role of seasonal sea-ice buttressing of the calving line. This will improve numerical models being developed of future changes to the Ross Ice Shelf.

We also prepared for future field seasons:

• The Antarctica New Zealand traverse team proved a route from our future Kamb Ice Stream drill site through heavily crevassed terrain to the drill site on Crary Ice Rise.
• Seismic and gravity survey campaigns commenced for future drilling targets at Discovery Deep to help ground truth a new bathymetric model for the Ross Sea.
• The possibility of establishing a future field camp was investigated on Mt Tuatara to expand the suite of cosmogenic samples used for investigating the retreat history of the Byrd Glacier.

Science highlights include several high impact publications, and the establishment of an international Antarctic drilling and research consortia.

A fundamental discovery by IODP (ocean drilling) Expedition 374 to the Ross Sea shows new evidence for the beginning of the West Antarctic Ice Sheet and the first marine based ice sheets to form around Antarctica as climate began to cool following global warmth in the Late Oligocene 24 million years ago. This research has important implications for the sensitivity of Antarctica's future marine-based ice sheets to increasing CO₂ concentration in the atmosphere.

A model-based reconstruction of Antarctic ice sheet retreat during the Last Interglaciation, a period of prolonged warmer-than-present climate that took place around 125,000 years ago. The study shows the implications for global sea-level change at the time for which sea-level is estimated to be +6-9m higher than today's requiring loss of West Antarctic Ice Sheet.

A modelling and data science study aimed to reduce uncertainty in the contribution of the Antarctic Ice Sheet to future sea-level rise projections. Historically constrained ice sheet simulations and a statistical emulator was used to demonstrate that a high-emissions signature of the Antarctic Ice Sheet sea-level contribution will not unambiguously emerge from the wide potential range of low-emission sea-level projections for over 100 years due to current limitations in our understanding in ice flow and sliding. These outcomes add to the growing body of Antarctic science that highlight the critical need to drastically reduce carbon dioxide emissions in the coming decades.

A 170-m-long sediment core collected from Integrated Ocean Drilling Program Site U1357B, offshore Adélie Land, East Antarctica was used to disentangle the impacts of sea ice and subdecadal climate variability on phytoplankton bloom frequency over the last ~11,400 years. Results from the study suggest that projected future loss of coastal sea ice will affect Antarctic margin primary productivity, altering food webs and carbon-cycling processes at seasonal timescales.

A key piece of research used geophysical data to better constrain the geology beneath the Ross Ice Shelf cavity. The analysis reveals basement surface and evidence of fault-controlled extensional basins. Active faults at Siple Coast likely influence ice streams through control of geothermal heat, groundwater, and glacioisostatic adjustments.

Two years of effort by the world's leading Antarctic researchers, including ASP team members, culminated in the release of a new 800 page book "Antarctic Climate Evolution", that will be the lead reference for post-graduate students and researchers in Antarctic glaciology, climate change, paleoclimatology, and oceanography. The book represents a major output for SCAR and the Antarctic Science Platform.

An International Continental Scientific Drilling Program (ICDP) proposal was accepted for the ASP-led SWAIS 2C (Sensitivity of the West Antarctic Ice Sheet to 2 degrees Celsius) project. This international consortium has co-funding commitments from collaborating partners in New Zealand, Germany, USA, UK, Australia, Japan, Italy and South Korea, and aims to understand the environmental conditions that will cause WAIS to collapse, when it will happen and just how fast it can retreat.

Antarctic Science Platform research outcomes underpin the latest generation of IPCC global sea-level projections and were used by NZSeaRise Programme. Our team supported a significant number of outreach activities and media reports for the release of the new sea level projections for New Zealand.