Don’t blame the air temperature: Sea warming is causing Antarctic glaciers to melt

Ocean warming has been uncovered as the primary cause of melting glaciers on the western Antarctic Peninsula.

The new study, carried out by scientists from Swansea University and the British Antarctic Survey, will enable researchers to better predict ice loss from this region – which is currently one of the largest contributors to sea-level rise.

Published today in the journal Science, the findings show that glaciers flowing to the coast on the western side of the Peninsula reveal a distinct spatial correlation with ocean temperature patterns. While those in the south retreat rapidly, those in the north show little change.

About 90% of the 674 glaciers in the Peninsula region have retreated since records began – in as recently as the 1940s.

Swansea University team leader Dr Alison Cook said: “Scientists know that ocean warming is affecting large glaciers elsewhere on the continent, but thought that atmospheric temperatures were the primary cause of all glacier changes on the Peninsula.

“We now know that’s not the case.”

melting-glacier

Environmental controls

Cook continues: “The numerous glaciers on the Antarctic Peninsula give a key insight as to how environmental factors control ice behaviour on a wide scale. Almost all glaciers on the western side end in the sea, and we’ve been able to monitor changes in their ice fronts using images as far back as the 1940s.

“Glaciers here are extremely diverse and yet the changes in their frontal positions showed a strong regional pattern.”

One of the aims of the study was to understand what was causing these differences, and in particular why glaciers in the north-west of the region showed less retreat than those located further south. Looking at the ocean temperature records has revealed this crucial link.

The scientists looked at ocean temperature measurements around the Peninsula dating back several decades, together with photography and satellite data for all 674 glaciers.

A strong pattern was determined between ocean temperatures and the north-south gradient of increasing glacier retreat: water is cold in the north-west and becomes increasingly warmer at depths below 100m further south.

Importantly, the research found that the warm water at mid-depths in the southerly region has been warming since the 1990s, at the same time as the acceleration in glacier retreat.

ice

Retreating glaciers

“These new findings demonstrate for the first time that the ocean plays a major role in controlling the stability of glaciers on the western Antarctic Peninsula,” co-author Professor Mike Meredith from the British Antarctic Survey adds.

“Where mid-depth waters from the deep ocean intrude onto the continental shelf and spread towards the coast, they bring heat that causes the glaciers to break up and melt. These waters have become warmer and moved the shallower depths in recent decades, causing glacier retreat to accelerate.”

A third author, Swansea’s Professor Tavi Murray, concludes: “The glaciers on the Antarctic Peninsula are rapidly changing – almost all of the Peninsula’s glaciers have retreated since the 1940s. We have known the region is a climate warming hotspot for a while, but we couldn’t explain what was causing the pattern of glacier change.

“This new study shows that a warmer ocean is the key to understanding the behaviour of glaciers on the Antarctic Peninsula. Currently the Peninsula makes one of the largest contributions to sea-level rise, which means understanding this link will improve predications of sea-level rise.”

Gecko-inspired robotic gripper to clear up space junk

Researchers have developed a pioneering robotic gripper that uses gecko-inspired sticky pads to clear up space debris.

Developed at Stanford University and NASA’s Jet Propulsion Laboratory (JPL), and detailed today in the journal Science Robotics, the gripper has been tested both on the ground and on the International Space Station, demonstrating that it can successfully operate in zero-gravity environments.

With around 500,000 pieces of man-made debris littering orbit, there is a growing need to successfully clear much of it so that humanity can safely increase its operations in low-Earth orbit. Each piece of space junk is whizzing around at up to 17,500 miles per hour, meaning a collision with a satellite, spacecraft or even astronaut would be extremely expensive and potentially very dangerous.

However, many conventional junk removal methods don’t work particularly well. Suction cups rely on creating a difference in air pressure, meaning they don’t work in a vacuum; magnets only work on a limited number of materials and debris harpoons risk missing and knocking the objects off in unpredictable directions.

Sticky solutions, then are preferred, however most tape-like solutions fail because the chemicals they rely on to make them sticky can’t cope with the massive temperature changes objects in space are subjected to. Which is where the gecko-inspired gripper comes in.

The robotic gripper being tested on NASA’s low-gravity aircraft the Weightless Wonder. Image, video  and featured image courtesy of Jiang et al., Sci. Robot. 2, eaan4545 (2017)

“What we’ve developed is a gripper that uses gecko-inspired adhesives,” said study senior author Mark Cutkosky, professor of mechanical engineering at Stanford. “It’s an outgrowth of work we started about 10 years ago on climbing robots that used adhesives inspired by how geckos stick to walls.”

Geckos are able to scale vertical surfaces because they have microscopic flaps that create weak intermolecular forces between the feet and the wall’s surface, allowing them to grip on. The researchers have simply replicated these flaps, albeit on a larger scale; while each flap on a gecko’s foot is around 200 nanometers long, on the robotic gripper it is only 40 micrometers across.

However, it works in the same way, allowing an object to be gripped in a zero-g environment without needing to apply force.

“If I came in and tried to push a pressure-sensitive adhesive onto a floating object, it would drift away,” said study co-author Dr Elliot Hawkes, a visiting assistant professor from the University of California, Santa Barbara. “Instead, I can touch the adhesive pads very gently to a floating object, squeeze the pads toward each other so that they’re locked and then I’m able to move the object around.”

A close-up of the prototype gripper. Image courtesy of Kurt Hickman/Stanford News Service

The gripper has already undergone extensive testing, including in JPL’s Robodome, which has a floor like a giant air hockey table that is designed to simulate a 2D zero-G environment.

“We had one robot chase the other, catch it and then pull it back toward where we wanted it to go,” said Hawkes. “I think that was definitely an eye-opener, to see how a relatively small patch of our adhesive could pull around a 300kg robot.”

Now it has been tested on the International Space Station, the next step is to test a version outside the space station, in the radiation-filled reality of space. Cutkosky also plans to commercialise the gecko-inspired adhesive here on Earth.

Human lifespan “could continue to increase far into the foreseeable future”

Scientists researching human lifespan have concluded that it has no detectable limit, and that with advances in technology and medicine it could continue to climb for the foreseeable future.

“We just don’t know what the age limit might be,” said study co-author Siegfried Hekimi, a biologist from McGill University.

“In fact, by extending trend lines, we can show that maximum and average lifespans could continue to increase far into the foreseeable future.”

The study, which is published today in the journal Nature, analysed the lifespan of the longest-surviving people from Japan, France, the UK and the US every year from 1968 to the present day.

The scientists found that there was no evidence that a limit on lifespan exists, and concluded that if it does, we certainly have not yet reached it or even identified what it could be.

The research flies in the face of previous studies that concluded that not only was there a limit of 115 years, but that we were beginning to reach it. However Hekemi and his colleague Bryan G Hughes do not believe this is the case, and are unable to even hazard a guess as to what such a limit could be.

“It’s hard to guess,” Hekimi said. “Three hundred years ago, many people lived only short lives.

“If we would have told them that one day most humans might live up to 100, they would have said we were crazy.”

Images courtesy of Jonathan Kos-Read

Average lifespans have jumped significantly over the past century. In 1920, Canadians had an average expectancy of 60 years, but by 1980 it had climbed to 76 years. Now it is 82 years, and is likely to climb further.

These jumps have been down to the revolution in medical science over the last hundred years, however advances in medical technologies could cause a significant further jump in our lifetimes.

In particular, work by organisations such as the SENS Research Foundation, led by noted gerontologist Aubrey de Grey, is focused on treating ageing as something that can be cured, and has seen growing support from the mainstream scientific community.

However, if such medical treatments do become available, they may only be available to those that can afford them, particularly in countries that do not have a single-payer healthcare system, such as the US. In these instances, there are fears that such treatments could divide humanity, with the rich gaining far longer lifespans than the poor.