We collected a bedrock core from Skytrain Ice Rise.
In 2018/19 a team of 6-8 people spent 8 weeks in a tented camp on Skytrain Ice Rise (79.74 S, 78.54 W). Drilling reached the bed at 651.04 metres depth. Drilling a core of this length to bedrock in a single field season is an exceptional achievement. Disseminated in a paper (Mulvaney et al 2021), and a Royal Society video.
We drilled with rapid access through Sherman Island.
In 2019/20 a small team used a rapid access drill to collect ice chips to 320 m, although bedrock was not attained. We established that the drill provides ice that can be analysed for isotopes and chemistry. Disseminated in two papers (Mulvaney et al., 2021; Rowell et al., 2022).
The data from Sherman Island provide unique climate records of the past millennium in a region where there is concern about the retreat of the ice sheet.
We completed a high depth-resolution record of the Holocene, last glacial and last interglacial at Skytrain Ice Rise.
After long hours in the cold room cutting the Skytrain ice core for analysis, we improved the continuous analysis system. In 2020 and 2021 we produced continuous records of water isotopes, methane and ionic impurities at resolution of order 4 cm along the entire core. Disseminated in a paper (Grieman et al 2022).
Several new methods were instituted and applied: total air content of the ice (providing evidence about past changes of elevation); laser ablation ICPMS, used on discrete sections of the core; sulfur isotope analysis, applied along the entire core (3 papers in preparation).
Skytrain shows a very interesting feature in the early Holocene, allowing us to date a period of rapid retreat of the ice shelf and consequent loss of inland ice. Major paper to be submitted soon.
Skytrain shows the expected pattern of climate change through the glacial period, but with isotopic change amplified by elevation changes at our site. Two papers are planned on this.
We dated the ice at both sites, showing the presence of last interglacial ice at Skytrain, and of ice 1000 years old at Sherman Island.
Both cores were dated near the top using volcanic markers (confirmed with sulfur isotope analysis) and annual layer counting. Beyond 2000 years the Skytrain core was dated by an inverse method using particularly the pattern of change in methane to tie our ice to previously dated cores. In the LIG there is some disturbance of the ice leading to a non-linear age scale and some folding. We were able to confirm that ice from ~117-126 ka (thousand years), in the LIG, is in good order, and to create a robust age model. Disseminated in a paper currently in review.
We used model output to investigate atmospheric (including water isotope) change under a range of WAIS scenarios.
Disseminated in a paper (Goursaud et al 2021).
We are completing an assessment of the timing and rate of changes in the Ronne Ice Shelf and WAIS between 140 and 100 ka (as well as at later times).
Although we are missing the very warmest section at the very start of the LIG, we can see from our data that by 126000 years ago, the Ronne Ice Shelf was at about its present position (based on sea salt), while the water isotopes suggest some retreat of WAIS. While it is possible there was greater retreat before 126 ka, this seems unlikely as ice would have had to regrow under warmest conditions. This important result suggests that the ice shelf is not as sensitive as some models suggested. This is being prepared for a high impact publication to be submitted in spring 2023.
