The West Antarctic Ice Sheet. Photo: Alex Michaud
Evidence from the Earth’s past is needed to determine the future. The Antarctic Science Platform and international collaborators are embarking on an exciting scientific drilling project, aiming to address the following questions:
What we don’t know about Antarctic ice melt
Earth’s average surface temperature has warmed by 1.2°C since the industrial revolution (1850) due to human activities that include burning of fossil fuels (coal, oil, and natural gas). At the same time, sea level has risen an average 20cm across the world, primarily due to the expansion of the ocean as it absorbs heat and melting of our planet’s glaciers, land-based ice caps and ice sheets.
We can expect further warming of between 1.5° to 4.5°C by 2100 - the size of the increase depends on what socio-economic decisions society makes about our greenhouse gas emissions. An additional 30cm of sea level rise is unavoidable regardless of our emissions decisions, but the increase may be as much as 1.5m if we follow a high-emissions pathway and potential instabilities in Antarctica’s ice sheets play out.
The dashed line in Figure 1 from the Intergovernmental Panel on Climate Change (IPCC) shows a low-likelihood, high-impact sea level response to a high emissions pathway. It’s a projection of what happens if the Antarctic ice sheets become unstable through processes that are physically possible but less certain. These processes are still being investigated by the scientific community.
Just how sensitive Antarctica’s large ice shelves - and the marine ice sheets that sit behind them - are to warming between 1.5 and 2°C is a key element of research that will help better predict when and how much the polar ice sheets might melt.
Scientists can look to the past for answers to that important question. Geological reconstructions from around the world indicate that sea levels were 6m higher than today during the last interglacial, 125,000 years ago. Earth’s average surface temperature was 1-1.5°C warmer than pre-industrial at that time. These data suggest that parts or all of the West Antarctic Ice Sheet collapsed, which highlights a potential sensitivity to temperatures that we have already reached, and will certainly experience in the coming decade. However, we have yet to obtain robust, direct evidence for that collapse.
“The discovery of our lifetime”
The Sensitivity of the West Antarctic Ice Sheet to Two Degrees of Warming (or SWAIS2C for short) is designed to determine whether the Ross Ice Shelf and West Antarctic Ice Sheet will melt as Earth’s average surface temperature reaches 1.5°C above those that characterised our planet before the industrial era. Similar temperatures previously occurred during the last interglacial period some 125,000 years ago, which makes this interval of time a great temperature analogue for our very near future.
During this time sea level was higher than today, and while there is some uncertainty as to the exact number, consensus suggests it was 6-9m higher than today.
These high sea level estimates suggest significant portions of the West Antarctic Ice Sheet (and parts of Greenland) must have melted. But we don’t have any clear and compelling evidence from next to the WAIS to confirm or refute this inference.
To address this shortcoming, our team of drillers, engineers and researchers will travel ~800 km via traverse and airplane to our two chosen locations and drill up to 200m below the sea floor beneath the Ross Ice Shelf to recover sedimentary records that may reveal key insight in West Antarctica’s past and the Earth’s future.
In mid-December 2023, we will use a custom-built hot water drill to melt a 30cm diameter hole through 590m of ice to access the 30m-thick water cavity near the grounding zone of the WAIS. (The grounding zone is the point where land ice begins to float and form an ice shelf.) We will then position a special sediment coring system over the hole and lower a diamond-studded hollow drill bit to the ocean floor, and drill down into what we anticipate are late Quaternary and Upper Neogene sediments. We will repeat the process in December 2024, at the Crary Ice Rise. A goal at this site is to recover Holocene and Upper Neogene sediments.
This is the first time anyone has attempted to obtain a long sedimentary record from well-below the seafloor so close to the centre of West Antarctica. This is ‘discovery science’ - there remains great uncertainty around the age and nature of what we will recover.
Our team calls SWAIS2C “the discovery of our lifetime”. Its objectives are important and may guide plans to adapt to unavoidable sea level rise, while amplifying an imperative to mitigate global greenhouse gas emissions, so that we may avoid the worst.
Astronauts have collected over 2400 samples from the moon since the first landing in 1969, but scientists and explorers have only managed to collect samples from beneath the ice that blankets West Antarctica at about 13 locations. We know more about the rocks and composition of the moon than we do about the land beneath the West Antarctic ice sheet. Whatever we recover and discover will be new to humankind.
Measuring how we walk the talk
Given the nature of our mission, we have carefully considered the carbon footprint of our project. Antarctic logistics and operations are fossil fuel intensive. As a climate-science focused project we believe we must understand, acknowledge and work to minimise the carbon we will emit as we strive to improve our understanding of Antarctic Ice Sheet response to warming produced by the burning of fossil fuels.
We’ve worked with Antarctica New Zealand and GNS Science to calculate the emissions that we will emit while we recover cores from Kamb Ice Stream. Our estimates include shipping, flights to and from Antarctica, fuel for our traverse and drilling operations. We will emit around 519 tonnes of CO2 equivalent. This is approximately the same amount of CO2 emitted by a single 787 Dreamliner plane full of passengers flying from London to Singapore.
Unfortunately, reducing these emissions is very difficult due to the Antarctic conditions and the technology that can deal with those conditions – we cannot replace diesel-powered PistenBully tractors with EVs or hydrogen-powered vehicles for a 800 km-long traverse across the ice shelf. At least not yet!
We are looking to offset our emissions, and firmly believe the cost of acquiring the materials and data that allow us to examine the sensitivity of the West Antarctic Ice Sheet are outweighed by the benefits. But the challenge for the future is clear – find a way to keep doing important research while minimising our impact on the planet.