In May 2025 around 80 scientists gathered in Edinburgh for a Royal Society Theo Murphy meeting to consider how geophysical data can be better collected and used for predicting global sea level, through improved ice-sheet modelling.
This incorporates many of these discussions, revealing how a new generation of researchers, ideas and equipment can improve ice-sheet bed measurements so that we may better predict global sea-level rise within the 21st Century and beyond. Guest Editor, Professor Martin Siegert, tells us more in this blog post.
Under continued burning of fossil fuels and consequent global warming, sea level will rise globally. But by how much? The doesn’t have a precise answer – ranging from below 0.5 to over 2.0 m by the end of this century, with increasing uncertainty thereafter. The problem is two-fold. The first depends on the ‘emissions pathway’ we choose to be on. Higher emissions lead to greater warming and, obviously, more ice loss. The second relates to our ability to predict sea level for any specific pathway. And for this we need numerical ice sheet models.
Ice sheets are having an increasingly dominant influence on global sea level, in ways not experienced since the last deglaciation between around 20-10,000 years ago. The gigantic Greenland and Antarctic ice sheets are losing mass at an alarmingly increasing rate. While the observations are clear, our ability to use ice sheet models to predict their future is compromised by a lack of geophysical (radar) measurements of the ice sheet bed.
In May 2025, around 80 scientists gathered in Edinburgh to discuss how to acquire ice sheet bed measurements in ways that will benefit modelling and reduce uncertainty in sea level rise predictions. In April 2026, a stemming from this meeting has been published.
Ice sheet bed measurements provide an essential boundary condition to models. For realistic models, the bed used as an input also needs to be realistic. And while the most recent digital elevation models of ice sheet beds are vastly improved, the data used to build them are not optimised for modelling, having been gathered over 60 years using different systems, resolutions, and orientations. The result is a collection of an irregular patchwork of datasets. While sophisticated interpolation schemes can help bridge between data points, they cannot replace the benefit of actual measurements.
It is entirely possible for the beds of both the Greenland and Antarctic ice sheets to be measured in a bespoke, comprehensive and systematic manner, in a way that can support modelling efforts. We know how to do this, especially with improved techniques like swath radar. Given that doing so would help understand global sea level rise much better, why haven’t we?
An obvious first reason is cost. Likely on the order of £250m to survey the entire Antarctic continent over five seasons, such investment would be a significant and atypical sum for a polar research programme. However, it should be split between countries and would only need to be done properly once to have multi-decadal benefits to Antarctic science and sea-level predictions. The ability to understand how to best adapt to rising sea level would vastly outweigh a necessary upfront cost. But, such funds do not exist in the budgets of national Antarctic operators, so support must come from non-traditional governmental routes. As the benefit would be far beyond Antarctica (and Greenland) this would be appropriate.
A second reason is building the international cooperation necessary to plan and execute the survey. International cooperation in bed measurements is excellent, however, with numerous examples of the international community building collaborations and agreements to survey whole catchments, and to provide freely existing data to update the ‘bedmap’ product, which is now in its third iteration. In other words, the international community is ready to work together. An upcoming opportunity exists to finally, after 60 years of preliminary work, measure the Antarctic and Greenland beds properly, as part of the (IPY5, 2032-33).
Finally, there is an urgency to improving ice sheet bed measurements. As the grounding lines retreat, the subglacial environment transitions to a submarine environment. Processes at the ice-water interface are crucial to ice sheet mass loss in Antarctica (and in Greenland) and critical to evaluating these is the bathymetry. Obtaining bathymetric measurements near the grounding line is far more difficult than using a radar to measure the ice sheet bed. So, it is an imperative to measure the entire Antarctic ice sheet grounding zone, and 10s of km upstream of it, so that what the grounding line migrates we already have detailed data of the newly created submarine system.
We have a chance to create an ice sheet geophysical data product that will benefit all of us for decades to come. Our discussions in Edinburgh, detailed in a new issue of , and planning for IPY5, can push us toward what’s required. We, and our future, will all benefit from improved ice-sheet bed measurements.
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