Cosmic clocks in Antarctic rocks: Forecasting future sea-levels by understanding the response of Byrd Glacier, East Antarctica, to climate change.

By Georgia Barrington-Smith & Dr Rebecca Duncan

The Antarctic ice sheet holds 61% of all the fresh water on Earth. How this ice sheet is responding to climate warming remains the biggest source of uncertainty in determining future global sea levels. Interpreting clues from the past ice margins is critical to understanding the future, and that’s where Lottie Stevenson comes in.

Lottie is an AINSE Pathway scholar and University of Wellington Honours student. In collaboration with ANSTO, she has investigated the deglacial (ice melting) history of Byrd Glacier, a critical East Antarctic outlet glacier. Byrd Glacier is the largest of the outlet glaciers draining ice from the East Antarctic ice sheet (EAIS), responsible for approximately 10% of the EAIS draining overall.

Lottie used cosmogenic nuclide surface exposure dating at ANSTO’s Centre for Accelerator Science (CAS) to determine the rate, timing, and magnitude of thinning ice at Byrd Glacier. She did this by extracting rare cosmogenic nuclides from glacial erratic cobbles, which are rocks deposited by the glacier as it thinned since the Last Glacial Maximum (LGM).  By pairing the two cosmogenic nuclides (long-lived ¹⁰Be and short-lived in-situ ¹⁴C), Lottie was able to determine the extent of post-LGM glacial thinning in the Ross Embayment. By understanding the Byrd Glacier’s past response to natural climatic changes, she is helping forecast future ice sheet change.

Ka mua, ka muri – ‘Walking backwards into the future’
(Māori proverb)

Lottie’s journey to the south pole

Lottie’s research took her to Antarctica, where she collected the erratic cobbles from the mountains adjacent to the Byrd Glacier fjord. These rocks were transported to Australia and crushed, allowing the quartz to be extracted, purified and eventually analysed by Lottie using accelerator mass spectrometry (AMS) at ANSTO’s Centre for Accelerator Science.

Her results revealed that the ice surface had thinned >600m since 7000 – 8000 years ago. This aligns with other studies that suggest the mid-Holocene was a time of rapid deglaciation across the Ross Embayment, whilst providing new knowledge that Byrd Glacier thinning was a more rapid and significant event than previously thought. These results are extremely useful for informing ice sheet modellers as they can strengthen numerical models used to predict future ice sheet and sea level response to climate change. This research is ongoing, and Lottie hopes to continue interpreting her results by performing a data-model comparison on them, and to derive a new inland paleo-thinning rate for Byrd Glacier.

Lottie’s experience with AINSE and ANSTO

Lottie was honoured to receive the AINSE Pathway Scholarship, as it allowed her to “…visit and experience state-of-the-art science at ANSTO”. Her Honours project exceeded her expectations, and she “…appreciated the site-wide tour, hands-on learning in the labs and AMS control room, and the friendly atmosphere of the CAS and AINSE teams”.

Lottie hopes to become an influential voice in Antarctic science, conservation, and decision-making – for she believes “…the icy continent is a unique place”.

We look forward to watching Lottie’s research journey as she looks to pursue a future PhD in polar science.