A DROP In the ocean
What new research can tell us about the future of the Greenland Ice Sheet.
WORDS SHANEY HUDSON
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For more than 12,000 years, the Greenland Ice Sheet has been the frozen heart of the Arctic. Ice core samples provide scientists with glimpses of what climate was like thousands of years ago. But as the world warms and the Greenland Ice Sheet (GIS) melts, scientists are now looking at the ice sheet’s past to predict its future. Their findings help us understand how the choices we make today will shape this wild and fragile landscape tomorrow – and the far-reaching consequences of a rapidly warming Greenland for the world.
A fine balance
Alongside Antarctica, the GIS holds 99 per cent of the world’s frozen freshwater. To measure the health of the GIS, scientists use a formula called Surface Mass Balance: the amount of snow added to the ice sheet less the amount lost from melting and evaporation. Previous research has shown the GIS was roughly stable during the nineteenth century and experienced variable mass loss in the twentieth century. In the past 20 years, however, the rate of ice loss has significantly increased. During summer 2019, the surface mass balance was the lowest on record.
To measure the health of the Greenland Ice Sheet, scientists use a formula called Surface Mass Balance: the amount of snow added to the ice sheet less the amount lost from melting and evaporation.
While recent data shows acceleration in ice loss, a new study published in Nature Journal set out to place this ice sheet loss within the context of a time period stretching back 12,000 years. Focusing on a section of Southwestern Greenland, a team of multidisciplinary scientists used state-of-the-art modelling to measure ice loss. First, they focused on the Holocene period 12,000 years ago, then on a second period from 1850 to 2012 using available historic data sets. Using these past and present models as a baseline, they then modelled a third, “future” period from 2015 to 2100. The future models used two benchmarks from the Representation Conservation Pathway (RCP), the greenhouse gas concentration trajectory adopted by the United Nations Intergovernmental Panel on Climate Change. A benchmark of RCP 2.6 – where globally there is a drastic reduction in carbon emissions to net-negative levels – is considered the best-case scenario. A benchmark of RCP 8.5 is considered a business-as-usual scenario, and relies on emissions continuing at their current rate. Under these future test scenarios, the study found ice loss is both sensitive to and influenced by emission levels. Researchers believe the current trend of GIS mass loss is following an RCP 8.5 trajectory. The research clearly establishes the GIS is shedding ice at an accelerated rate, but also flags the sobering possibility that the GIS may be gone in as little as a thousand years.
Why it matters
One of the biggest implications of the GIS melting is sea level rise. “The Greenland Ice Sheet holds the equivalent of about seven metres of potential sea level rise,” says University of Washington researcher Jessica Badgeley who took part in the study. “It’s such a large store of fresh water that melting just some of it, and even raising sea level by centimetres or inches, will have a large impact on coastal communities across the world.” The environmental, social and economic impact of sea level rise is already being seen in low-lying coastal islands such as Kiribati and the Solomon Islands, as well as more industrialised nations like the United States.
A rise in sea level can lead to flooding, salinisation of the soil, erosion, loss of biodiversity and, in the most extreme cases, entire islands taken by rising waters, forcing communities to relocate. Other complications from ice loss include changes in ocean circulation patterns, weather and climate. “The Greenland Ice Sheet is part of our broader Arctic system, and it plays a pivotal role in regulating global climate,” says University of California researcher Joshua Cuzzone, who also collaborated on the study. “So when the Greenland Ice Sheet changes course, that’s linked to changes in our global climate as well.”
Where to now?
Regardless of whether the RCP 2.6 benchmark is met, the GIS will continue to melt. “I think one thing that’s important to stress is that … even if we were to curb our greenhouse gas emissions, we’re still committed to a certain amount of warming,” says Cuzzone. “We’re still committed to a certain amount of sea level rise.” However, Cuzzone and Badgeley maintain a key takeaway from the research is that we can influence Greenland’s future. “I think a big implication of this study is that you can make a difference and, as a global society, if we follow these lower emissions scenarios and high mitigation scenarios, we’ll have an impact on what happens to those ecosystems,” says Badgeley. “We, as humans, can make decisions that will very likely have a huge impact on what happens in the future.”