Professor and climate researcher Shfaqat Abbas Khan from DTU Space and his colleagues have made a surprising discovery deep within Greenland’s ice sheet. This finding is one of many components that will be part of a new and very precise climate model. The model aims to predict how high sea levels will rise in at-risk coastal areas around the globe as ice continues to melt in the Arctic and Antarctic.
“It was while collecting data for the model that we observed snow and ice melting as high as 3.5 kilometers up in central Greenland - an area typically expected to remain cold and dry,” says Shfaqat Abbas Khan.
“That snow is melting here and not being replenished is something new. This knowledge can help us make our model more precise”.
20 experts working at a dedicated research center
Abbas Khan leads the research center CISP - Center for Ice-sheet and Sea-level Predictions - at DTU Space. The center was established two years ago with support from the Novo Nordisk Foundation and will receive funding for a total of six years to develop the model. Around 20 researchers from DTU Space, GEUS, the University of Copenhagen, and Dartmouth College in the U.S. are collaborating on the effort.
“Our major goal is to develop a model that can precisely predict how sea-level rise will impact coastlines under different global warming and ice melt scenarios - from Miami and Dubai to Esbjerg and Copenhagen,” says Abbas Khan.
“We expect to have a first prototype ready within the next two years”.
Progress on a very massive task
It’s a monumental challenge, the researchers are facing. But the work is progressing.
The new discovery on the ice sheet represents just a small part of a much bigger equation. The model also includes data on global temperature increases and the movement of ice masses from land into the sea.
In addition, researchers are studying how much surface meltwater seeps beneath the ice and flows out into the ocean. That meltwater acts like a lubricant, causing the overlying ice to slide more quickly toward the sea, where it melts.
“One of the important parameters is being able to predict which parts of the ice sheet risk collapsing - and when. Such events would result in surges in melting and therefore accelerate sea-level rise,” says Abbas Khan.
To calculate ice loss and the resulting sea-level rise, the researchers use a combination of satellite measurements and GPS stations placed on Greenland’s ice and bedrock.
The first model is ready
The first major milestone has been the development of a model that more accurately depicts what have happened over the past 30-40 years. That model is now in place.
“We’ve achieved quite a bit. During the first two years, we focused on gathering observations and building models based on altimetry - satellite data measuring the ice - supplemented by GPS data from stations on bedrock and ice in Greenland. The goal was to determine when, where, and how large glaciers are thinning and losing mass,” explains Shfaqat Abbas Khan.
“Using satellite data, we’ve also developed an initial baseline model that shows, in very high resolution, how much ice that has melted month by month over the past 30 years. Such a detailed record hasn’t been created before - most often, the trends are summarized in 1-, 5-, or 10-year intervals.”
At this stage, it’s been crucial to ensure that the model aligns with actual observations.
“That’s gone well, and we consider it a major milestone in our work,” says Shfaqat Abbas Khan.
From historical data to future scenarios
In the next phase, the researchers will develop models that can recreate observed data without being directly based on measurements. The big goal is to make predictions about future observations.
“We can now start incorporating and adjusting parameters like temperature - which both accelerates ice melt and causes ocean water to expand - as well as the technical details of melting in different locations and the associated feedback effects. Then we can begin forecasting future developments,” says Khan.
Strong demand for sea-level predictions
So far, the research center has produced 12 peer-reviewed scientific articles, with more underway in top journals such as Nature and Science.
The UN’s climate panel, the IPCC, estimates that sea levels could rise by 0.6 to 2 meters by 2100, affecting as many as 630 million people.
“With our forthcoming model, it will be possible to predict much more accurately how sea levels will change in specific areas. This is crucial for planning and adaptation - something that both the UN and many nations are calling for,” says the professor.
Overlooked processes and details ensure precision
To build the most accurate model possible, researchers focus especially on understanding new and overlooked processes that affect ice movement and melting - for example, the melting on high ground in central Greenland that produces water flowing both on the surface and deep into and beneath the ice sheet.
They are also working with much higher levels of detail than before, capturing small changes and seasonal variations. It’s primarily the combination of satellite data and GPS readings from stations across Greenland that enables the creation of such accurate models.
GPS sensors detect changes in the elevation of the ice or bedrock caused by melting. From this, the amount of meltwater can be calculated. These sensors can also detect slight shifts in ice movement that satellites can’t pick up.
“GPS measurements on the ice have shown us that meltwater from the surface doesn’t just refreeze after reaching the base. It continues to flow, which speeds up the ice above it while also flowing into the sea. We published an article about this in Nature,” says Khan.
“This suggests the ice doesn’t move evenly or linearly. That may be due to complex drainage mechanisms under the ice, which we’re still trying to understand better. It’s important because we expect these phenomena to become more common as more meltwater lakes form on the ice surface due to warmer temperatures.”
Fieldwork on the ice is essential for reliable data
Fieldwork in the Arctic is vital for gathering the accurate data needed to build reliable models.
DTU Space has expertise in GPS measurements, and researchers both retrieve data from and maintain the GPS stations in Greenland on behalf of the Danish Climate Data Center, which owns them.
During the summer, Shfaqat Abbas Khan and colleagues visited Greenland several times. Their task was to ensure that the GPS stations were ready for measurements throughout the summer, when ice melt and glacier movement are at their peak. Later they went on an expedition to the Petermann Glacier in Northwest Greenland - one of the most inaccessible areas i Greenland - to carry out precise measurements on the ice.
“Conditions on Greenland’s ice sheet are harsh, but it’s vital to take direct measurements from the ice to make our models as accurate as possible,” says Khan.
693 cubic kilometers of ice have melted annually since 2000
With global warming, ice melt is accelerating. So far, about 693 gigatons - approximately 693 cubic kilometers - of ice have melted into the world’s oceans each year since 2000.
In the Arctic, the melting is concentrated in around 20-30 glaciers in Greenland. The largest contributor to sea-level rise is Jakobshavn Glacier in western Greenland, about 550 kilometers north of Nuuk.
Antarctica is also increasingly contributing to rising seas. That could significantly impact water levels along Denmark’s coasts in the future.
“When Antarctic ice melts, sea levels tend to rise more in the northern hemisphere -including Denmark - because the water is drawn in that direction. Conversely, melting in Greenland initially causes sea levels to shift southward, raising water levels in the southern hemisphere. That makes it especially important to predict developments in both regions with high precision,” Khan says.
This brings us back to the detailed global sea-level map the CISP-team is working on:
“When our model is ready, we’ll be able to test different climate scenarios and see how the ice and sea levels evolve. That will give us a global sea-level map showing, city by city, which places are most at risk from rising seas by the year 2100,” concludes Shfaqat Abbas Khan.
