Skip to main content

Greenland is melting: we need to worry about what’s happening on the largest island in the world

Jonathan Bamber, Author provided

Greenland is the largest island in the world and on it rests the largest ice mass in the Northern Hemisphere. If all that ice melted, the sea would rise by more than 7 metres.

But that’s not going to happen is it? Well not any time soon, but understanding how much of the ice sheet might melt over the coming century is a critical and urgent question that scientists are trying to tackle using sophisticated numerical models of how the ice sheet interacts with the rest of the climate system. The problem is that the models aren’t that good at reproducing recent observations and are limited by our poor knowledge of the detailed topography of the subglacial terrain and fjords, which the ice flows over and in to.

One way around this problem is to see how the ice sheet responded to changes in climate in the past and compare that with model projections for the future for similar changes in temperature. That is exactly what colleagues and I did in a new study now published in the journal Nature Communications.

We looked at the three largest glaciers in Greenland and used historical aerial photographs combined with measurements scientists had taken directly over the years, to reconstruct how the volume of these glaciers had changed over the period 1880 to 2012. The approach is founded on the idea that the past can help inform the future, not just in science but in all aspects of life. But just like other “classes” of history, the climate and the Earth system in future won’t be a carbon copy of the past. Nonetheless, if we figure out exactly how sensitive the ice sheet has been to temperature changes over the past century, that can provide a useful guide to how it will respond over the next century.

A man walks over grassy land with glacier in background
Greenland’s glaciers contain around 8% of the world’s fresh water. Jonathan Bamber, Author provided

We found that the three largest glaciers were responsible for 8.1mm of sea level rise, about 15% of the whole ice sheet’s contribution. Over the period of our study the sea globally has risen by around 20cm, about the height of an A5 booklet, and of that, about a finger’s width is entirely thanks to ice melting from those three Greenland glaciers.

Melting As Usual

So what does that tell us about the future behaviour of the ice sheet? In 2013, a modelling study by Faezeh Nick and colleagues also looked at the same “big three” glaciers (Jakobshavn Isbrae in the west of the island and Helheim and Kangerlussuaq in the east) and projected how they would respond in different future climate scenarios. The most extreme of these scenarios is called RCP8.5 and assumes that economic growth will continue unabated through the 21st century, resulting in a global mean warming of about 3.7˚C above today’s temperatures (about 4.8˚C above pre-industrial or since 1850).

This scenario has sometimes been referred to as Business As Usual (BAU) and there is an active debate among climate researchers regarding how plausible RCP8.5 is. It’s interesting to note, however, that, according to a recent study from a group of US scientists it may be the most appropriate scenario up to at least 2050. Because of something called polar amplification the Arctic will likely heat up by more than double the global average, with the climate models indicating around 8.3˚C warming over Greenland in the most extreme scenario, RCP8.5.

Despite this dramatic and terrifying hike in temperature Faezeh’s modelling study projected that the “big three” would contribute between 9 and 15 mm to sea level rise by 2100, only slightly more than what we obtained from a 1.5˚C warming over the 20th century. How can that be? Our conclusion is that the models are at fault, even including the latest and most sophisticated available which are being used to assess how the whole ice sheet will respond to the next century of climate change. These models appear to have a relatively weak link between climate change and ice melt, when our results suggest it is much stronger. Projections based on these models are therefore likely to under-predict how much the ice sheet will be affected. Other lines of evidence support this conclusion.

What does all of that mean? If we do continue along that very scary RCP8.5 trajectory of increasing greenhouse gas emissions, the Greenland ice sheet is very likely to start melting at rates that we haven’t seen for at least 130,000 years, with dire consequences for sea level and the many millions of people who live in low lying coastal zones.The Conversation

--------------------------

This blog is written by Cabot Institute member Jonathan Bamber, Professor of Physical Geography, University of BristolThis article is republished from The Conversation under a Creative Commons license. Read the original article.

Professor Jonathan Bamber


Popular posts from this blog

Are you a journalist looking for climate experts? We've got you covered

We've got lots of media trained climate change experts. If you need an expert for an interview, here is a list of Caboteers you can approach. All media enquiries should be made via  Victoria Tagg , our dedicated Media and PR Manager at the University of Bristol. Email victoria.tagg@bristol.ac.uk or call +44 (0)117 428 2489. Climate change / climate emergency / climate science / climate-induced disasters Dr Eunice Lo - expert in changes in extreme weather events such as heatwaves and cold spells , and how these changes translate to negative health outcomes including illnesses and deaths. Follow on Twitter @EuniceLoClimate . Professor Daniela Schmidt - expert in the causes and effects of climate change on marine systems . Dani is also a Lead Author on the IPCC reports. Dani will be at COP26. Dr Katerina Michalides - expert in drylands, drought and desertification and helping East African rural communities to adapt to droughts and future climate change. Follow on Twitter @_k

Urban gardens are crucial food sources for pollinators - here’s what to plant for every season

A bumblebee visits a blooming honeysuckle plant. Sidorova Mariya | Shutterstock Pollinators are struggling to survive in the countryside, where flower-rich meadows, hedges and fields have been replaced by green monocultures , the result of modern industrialised farming. Yet an unlikely refuge could come in the form of city gardens. Research has shown how the havens that urban gardeners create provide plentiful nectar , the energy-rich sugar solution that pollinators harvest from flowers to keep themselves flying. In a city, flying insects like bees, butterflies and hoverflies, can flit from one garden to the next and by doing so ensure they find food whenever they need it. These urban gardens produce some 85% of the nectar found in a city. Countryside nectar supplies, by contrast, have declined by one-third in Britain since the 1930s. Our new research has found that this urban food supply for pollinators is also more diverse and continuous

#CabotNext10 Spotlight on City Futures

In conversation with Dr Katharina Burger, theme lead at the Cabot Institute for the Environment. Dr Katharina Burger Why did you choose to become a theme leader at Cabot Institute ? I applied to become a Theme Leader at Cabot, a voluntary role, to bring together scientists from different faculties to help us jointly develop proposals to address some of the major challenges facing our urban environments. My educational background is in Civil Engineering at Bristol and I am now in the School of Management, I felt that this combination would allow me to build links and communicate across different ways of thinking about socio-technical challenges and systems. In your opinion, what is one of the biggest global challenges associated with your theme? (Feel free to name others if there is more than one) The biggest challenge is to evolve environmentally sustainable, resilient, socially inclusive, safe and violence-free and economically productive cities. The following areas are part of this c