A new source of melting at the bottom of ice sheets could mean they thaw more quickly and raise sea levels faster than previously thought.

Ice sheets, glacial features which cover an area greater than 50,000 square kilometres, are difficult to measure at their base because of the ice depth. This makes it hard to model the dynamics by which they move and melt.

Now, at the University of Cambridge and his colleagues have found a way to measure the rate of melting underneath the Greenland ice sheet, the second largest ice sheet in the world, using radar with a wavelength of just a few millimetres and direct borehole measurements.

Christoffersen and his team found that the rate of melting at the bottom of a vertical crack which water flows down was 100 times greater than previous estimates, almost as high as the melting at the sun-exposed surface. They think the enhanced effect comes from the conversion of gravitational energy that the meltwater has at the surface into heat as it trickles downwards, which drives the melting of the ice at the bottom.

“Models do not include this effect, but it’s actually quite substantial,” says Christoffersen. “The melting that’s generated through this process is several orders of magnitude higher than [melting from] other heat sources such as friction and geothermal heat flux [meaning the effect of heat from Earth’s interior].”

The Greenland ice sheet is already thought to be the largest global contributor to sea level change, but this new effect could make it an even larger source. Christoffersen and his team estimate that, as more meltwater is generated at the surface in future, the heat source [at the base] could grow to be seven times as large as it is today by 2100. Because the heating comes from gravity, it could mean that other deep ice sheets also have a higher rate of melting than previously thought.

“There’s clearly an energy component missing in the models that we’re using to try and predict the dynamic contribution to sea level change,” says Christoffersen.

The long-term picture for sea level rise is uncertain, he says. As an ice sheet melts and shrinks in height, this effect could become a greater source of heat as more meltwater trickles down. But if meltwater at the bottom of the ice sheet flows more rapidly into the sea in future, it may have less time to cause further melting.

What you can expect

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At 91av 91av our mission is to cut through the uncertainty around the current job market and��give you the very best insight into your industry.

To do this, we need your help.��

We’ve teamed up with specialist STEM recruitment agency SRG to provide you with the latest insights into your industry. We will benchmark salary data, employment satisfaction and discrimination in the workplace.

The survey shouldn’t take more than 10 minutes to complete and, as a thank you, all respondents who complete the survey will be entered into a prize draw to win one of five £100 Amazon vouchers (or local equivalent). The information you provide will only be used in aggregate and your views will be completely confidential in accordance with the UUK Market Research Society’s Code of Conduct.

The report will be available in a forthcoming issue of 91av. Be part of the conversation and participate today!

These are difficult times – for individuals, companies and nations. These are��also terrible times for many charities, whose donations may have dried up, and who may no longer be able to operate as they once did. For the people or the wildlife depending on those charities, locally and across the globe, things may be worse still.

This is why��91av��is launching a��project called Signal Boost.

The idea is simple: if you are a charitable organisation involved in��science, technology, medicine or��conservation, and you would like to��speak directly to��91av��readers, then you can have a page in the magazine to advertise what you do and why that is worthy of support, free of charge. Simply email��chris.martin@newscientist.com��to explain why you would like to take part in the project.

If your organisation doesn’t quite fit the description above, but��you want to take part, then do��drop us a line explaining why you deserve a slot anyway!

To kick this off, we have been delighted to “boost the signal” for��two��highly admirable charities in the 16 May issue of��91av: , which works with deprived children and their families��across the globe, and ,��which promotes social mobility and diversity in STEM in the UK. We look forward to featuring many more.

Add some science to your lockdown living routine, as we make some of the incredible talks from our flagship science festival available for free on .

What’s the plan?

For the past two years at 91av Live, we have been filming talks on five stages with different themes: cosmos, Earth, humans, engineering and technology stages – as well as keynote speakers on our main stage. If you’re a subscriber you watch them all on our website, but now we’re releasing a selection of them more widely.

What’s available?

Starting Monday 6 April, each week, we’ll be making talks by world-leading thinkers available for free. Check out our to see what’s coming up next.

And check out everything we’ve shared so far:

• Harvard geneticist is DNA testing the bones of ancient humans to discover the truth about us, and where we came from.
• The bacteria in your gut are vital to your physical and mental health. shows how to look after them.
• Astronaut and explorers Nics Wetherill and Will Millard tell stories of life in space and adventures to the wild corners of Earth.
• reveals the full scale of the ocean plastic crisis and explores how science can offer solutions.
• tells the amazing tale of Homo naledi, and explains why stunning fossil finds mean we need to rewrite our family tree.
• Thrill engineer explains how he designs the whitest of white-knuckle rides.
• argues that it’s just a matter of time before we hear from alien civilisations.
• Astronomer Royal�� makes some predictions on humanity’s future.
• Director of the UK’s National Space Academy asks if humans will ever make it to Mars.
• Join as he explains how he made the world’s most precise thermometer.
• looks at the psychology of video games, and asks: can they really harm us?
• explores the secret lives of parasites
• speaks about how modern lifestyles are disrupting the body’s light-dark cycle
• discuss whether ancient views about the mind be reconciled with modern neuroscience
• Mathematician explains his love of numbers, and their hidden wonders
• Psychologist demonstrate how our minds are so easily deceived by magic
• Join writer and campaigner as she explores the gender data gap
• See exploring the wonders of the solar system
• Check out on the truth about diets
• Tune in to theoretical physicist as he tells us about the nature of time
• Molecular biologist fills us in on the CRISPR genome editing revolution
• Neuroscientist asks if free will is an illusion, or if we can choose our fate
• Join mathematician to answer the question: “Can AI be creative?

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Why?

With the stay-at-home measures looking set to continue for many weeks, we couldn’t think of a better way to keep our readers’ minds active and entertained.

Who can I watch?

Some of the greatest minds in science, including Lee Berger, the discoverer of our ancient human relatives Homo naledi; leading psychopharmacologist Val Curran on the science of medicinal cannabis; Nobel prizewinning astronomer Didier Quleoz who discovered the first planet orbiting a star outside the solar system; and award-winning campaigner and bestselling author Caroline Criado Perez on the shocking gender data gap. And many, many more.

Will there be anything I can watch with the kids?

91av Live is hugely popular with families. Watch our most popular family-friendly talks together – or, if you’re apart, make a date to view and chat afterwards. Geneticist Giles Yeo will kick off with the truth about diets; discover the secret life of dogs with the RSPCA’s Samantha Gaines; what happened to the dinosaurs with palaeontologist Steve Brusatte; and hear astronaut Tim Peake share fascinating tales from around the world and beyond with Antarctic and jungle adventurers. Pete Etchells talk about whether video games are bad for us is sure to strike a chord among families at the moment.

Anything educational?

Plenty. Our 2019 show had a dedicated schools’ programme for the first time and we’re releasing all of the talks, kicking off with astronomer Sheila Kanani on the wonders of the solar system. Gain a new appreciation of numbers with mathematician and teacher Bobby Seagull; hear how inspirational designer and engineer Sam Rogers built his own Iron Man-style jetsuit; learn about technology from rapper Jon Chase; how AI will change the future of work from computing prodigy Anne Marie Imafidon and discover how gene editing is transforming biology with Helen O’Neill.

How can I view them?

On our YouTube channel,

Our shiny new podcast brings you the most important, startling or just plain weird happenings in the world of science.

Presented each week by 91av’s Rowan Hooper (podcast editor) and Penny Sarchet (news editor), with guests from our expert editorial staff, the Weekly gives you the inside knowledge on three must-know stories from the past week.

Introduced with our unique blend of verve, insight and extraordinary attention to detail, the show is essential listening for anyone interested in how the world works, how life evolved… and whether the creation of a nano-sized wormhole in the fabric of space-time is a cause for concern.

“I’m really excited to launch this excellent new podcast from 91av,” says Rowan. “There are so many important and entertaining developments in science and technology each week, and we can’t wait to tell you everything you need to know about them,” says Penny.

New episodes go live each Friday, and are available on all the usual places you get your podcasts: iTunes/Apple Podcasts, Spotify, Stitcher, TuneIn/Alexa. You can find them all at newscientist.com/podcasts. We also have a dedicated Twitter feed for the show, .

Watch this space for two more 91av podcasts, launching soon. Join us each week to keep up to date with the latest science breakthroughs and discoveries. But mostly to massively impress your friends with your brilliant science knowledge.

The three new podcasts are a joint venture between 91av and Right Angles.

Ollie Guillou, head of podcasts at Right Angles said:

“Right Angles has a great track record of podcast production, from the nature series Trees A Crowd with David Oakes to the Tech Against Terrorism podcast. This is the start of a brilliant and fruitful relationship with the world’s best loved science magazine, and it’s incredibly exciting to work with top journalists at 91av.”

Meet our hosts

Rowan has been at 91av 15 years. He has a PhD in evolutionary biology and worked as a biologist in Japan before becoming Science Editor of the Japan Times in Tokyo. He has also written for The Guardian, The Washington Post, The Wall Street Journal and The Economist.��His first book, published in 2018, is��Superhuman: Life at the Extremes of Mental and Physical Ability. Follow him on Twitter

Penny is 91av’s news editor. She previously specialised as a reporter and editor covering health, biology and science policy, and has a DPhil in developmental genetics. She has also written for The Guardian, BBC Science Focus, Nature, Mosaic and The Telegraph. She tweets at @

Listen to the first episode now at newscientist.com/podcasts, or wherever you get your podcasts

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Fat, oil and grease (FOG) in sewers, like in our blood vessels, can accumulate and produce hard deposits which interfere with the sewage flow. will explain at 91av live how these deposits grow bigger over time and can become huge underground fatbergs, composed of saponified fats congealed with non-flushable products.

Based at De Montfort University, Villa is an expert on microbial bioengineering and uses her particular expertise in microbial and enzymatic processes in the environmental sectors.

is the world’s greatest science festival and runs from 10 to 13 October at ExCel London. You can .