Climate scientists explore hidden ocean beneath Antarctica’s largest ice shelf



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The team used hot-water drilling gear to melt a hole through Antarctica’s Ross Ice Shelf to explore the ocean below.
Christina Hulbe, CC BY-ND

Craig Stevens and Christina Hulbe

Antarctica’s Ross Ice Shelf is the world’s largest floating slab of ice: it’s about the size of Spain, and nearly a kilometre thick.

The ocean beneath, roughly the volume of the North Sea, is one of the most important but least understood parts of the climate system.

We are part of the multi-disciplinary Aotearoa New Zealand Ross Ice Shelf programme team, and have melted a hole through hundreds of metres of ice to explore this ocean and the ice shelf’s vulnerability to climate change. Our measurements show that this hidden ocean is warming and freshening – but in ways we weren’t expecting.

Instruments travelling 360m down a bore hole, from the snow-covered surface of the Ross Ice Shelf through to the ocean below the ice. After splash-down at about 60m, they move through the bubble-rich upper ice and down into the dark bubble-free lower reaches of the ice – passing embedded sediment that left the coast line centuries ago.



Read more:
Antarctic glacier’s unstable past reveals danger of future melting


A hidden conveyor belt

All major ice shelves are found around the coast of Antarctica. These massive pieces of ice hold back the land-locked ice sheets that, if freed to melt into the ocean, would raise sea levels and change the face of our world.

An ice shelf is a massive lid of ice that forms when glaciers flow off the land and merge as they float out over the coastal ocean. Shelves lose ice by either breaking off icebergs or by melting from below. We can see big icebergs from satellites – it is the melting that is hidden.

Because the water flowing underneath the Ross Ice Shelf is cold (minus 1.9C), it is called a “cold cavity”. If it warms, the future of the shelf and the ice upstream could change dramatically. Yet this hidden ocean is excluded from all present models of future climate.

This satellite map shows the camp site on the Ross Ice Shelf, Antarctica.
Ross Ice Shelf Programme, CC BY-ND

There has only been one set of measurements of this ocean, made by an international team in the late 1970s. The team made repeated attempts, using several types of drills, over the course of five years. With this experience and newer, cleaner, technology, we were able to complete our work in a single season.

Our basic understanding is that seawater circulates through the cavity by flowing in at the sea bed as relatively warm, salty water. It eventually finds its way to the shore – except of course this is a shoreline under as much as 800 metres of ice. There it starts melting the shelf from beneath and flows across the shelf underside back towards the open ocean.

Peering through a hole in the ice

The New Zealand team – including hot water drillers, glaciologists, biologists, seismologists, oceanographers – worked from November through to January, supported by tracked vehicles and, when ever the notorious local weather permitted, Twin Otter aircraft.

As with all polar oceanography, getting to the ocean is often the most difficult part. In this case, we faced the complex task of melting a bore hole, only 25 centimetres in diameter, through hundreds of metres of ice.

A team of ice drillers from Victoria University of Wellington used hot water and a drilling system developed at Victoria to melt a hole through hundreds of metres of ice.
Craig Stevens, CC BY-ND

But once the instruments are lowered more than 300m down the bore hole, it becomes the easiest oceanography in the world. You don’t get seasick and there is little bio-fouling to corrupt measurements. There is, however, plenty of ice that can freeze up your instruments or freeze the hole shut.

A moving world

Our camp in the middle of the ice shelf served as a base for this science, but everything was moving. The ocean is slowly circulating, perhaps renewing every few years. The ice is moving too, at around 1.6 metres each day where we were camped. The whole plate of ice is shifting under its own weight, stretching inexorably toward the ocean fringe of the shelf where it breaks off as sometimes massive icebergs. The floating plate is also bobbing up and down with the daily tides.

The team at work, preparing a mooring.
Christina Hulbe, CC BY-ND

Things also move vertically through the shelf. As the layer stretches toward the front, it thins. But the shelf can also thicken as new snow piles up on top, or as ocean water freezes onto the bottom. Or it might thin where wind scours away surface snow or relatively warm ocean water melts it from below.

When you add it all up, every particle in the shelf is moving. Indeed, our camp was not so far (about 160km) from where Robert Falcon Scott and his two team members were entombed more than a century ago during their return from the South Pole. Their bodies are now making their way down through the ice and out to the coast.

What the future might hold

If the ocean beneath the ice warms, what does this mean for the Ross Ice Shelf, the massive ice sheet that it holds back, and future sea level? We took detailed temperature and salinity data to understand how the ocean circulates within the cavity. We can use this data to test and improve computer simulations and to assess if the underside of the ice is melting or actually refreezing and growing.

Our new data indicate an ocean warming compared to the measurements taken during the 1970s, especially deeper down. As well as this, the ocean has become less salty. Both are in keeping with what we know about the open oceans around Antarctica.

We also discovered that the underside of the ice was rather more complex than we thought. It was covered in ice crystals – something we see in sea ice near ice shelves. But there was not a massive layer of crystals as seen in the smaller, but very thick, Amery Ice Shelf.

Instead the underside of the ice held clear signatures of sediment, likely incorporated into the ice as the glaciers forming the shelf separated from the coast centuries earlier. The ice crystals must be temporary.

None of this is included in present models of the climate system. Neither the effect of the warm, saline water draining into the cavity, nor the very cold surface waters flowing out, the ice crystals affecting heat transfer to the ice, or the ocean mixing at the ice fronts.

The ConversationIt is not clear if these hidden waters play a significant role in how the world’s oceans work, but it is certain that they affect the ice shelf above. The longevity of ice shelves and their buttressing of Antarctica’s massive ice sheets is of paramount concern.

Craig Stevens, Associate Professor in Ocean Physics and Christina Hulbe, Professor and Dean of the School of Surveying (glaciology specialisation)

This article was originally published on The Conversation. Read the original article.

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Hidden housemates: when possums go bump in the night


Emma Power, Western Sydney University and Jane DeGabriel, Western Sydney University

You’re drifting off to sleep when, suddenly, there’s a bump and a thump and an unearthly shriek. But never fear, if your home is making these noises you probably don’t have ghosts, but a family of common brushtail possums.

Researchers have documented 18 different brushtail possum sounds. These include “grunting, growling, hissing, screeching, clicking and teeth-chattering calls, many of which would not be out of place on a horror movie soundtrack”.

Common brushtail possums (Trichosurus vulpecula) live across much of suburban Australia. Although often associated with bushland environments and commonly considered a tree-dweller, these adaptable creatures are also highly attracted to human houses.

The biggest hidden housemate?

Despite being the same size as a domestic cat, these lively, nocturnal marsupials frequently make their dens in the ceiling and wall cavities of homes. In fact, one study of possums in urban Tasmania found that 87% of their visits to dens were associated with buildings (mostly older houses), while 45% of den visits were to roof cavities.

These hidden animals make themselves known to their human housemates as they run across the ceiling. A Sydney study found that as many as 67% of people whose properties were visited by possums heard possum activity on or in roof cavities, while 58% reported possums living in these spaces.

A young possum discovers pineapple, via mum.
Peter Firminger/Flickr, CC BY

Possums in the city

At the time of European arrival, common brushtail possums were abundant across mainland Australia and Tasmania. However, intensive hunting for a burgeoning fur trade in the 19th and early 20th centuries led to a drastic decline in possum numbers. Since the end of hunting, habitat degradation and fragmentation, fires and fox predation have put further pressure on possum populations. In contrast, they appear to be flourishing in our cities.

Common brushtail possums are territorial creatures, usually sleeping alone during the day in dens in tree hollows, rock piles or logs. Dens are often in limited supply in the bush and possums will compete for nesting sites, sometimes fighting to the death. In contrast, suburbia provides an abundance of potential nesting spaces.

In fact, urban possums seem to prefer living in human-built structures, even when hollow trees are available. A single roof can provide a home for many cohabiting possums, although disputes among roommates may become raucous.

Abundant food and a broad palate mean people and possums were made for each other.
Peter Firminger/Flickr, CC BY

Another reason that brushtail possums have adapted so successfully to our cities is their generalised diet. Unlike specialised eucalypt feeders like the koala, brushtail possums eat the leaves, flowers and fruit of a range of native and exotic plants, as well as Eucalyptus leaves. They also sometimes eat insects and bird eggs.

Thus suburban gardens, with their abundance of fruit trees, roses and vegie patches, provide a “possum supermarket”, conveniently offering a diverse array of tasty, nutritious foods year round – much to the frustration of many gardeners!

In a study in eucalypt woodlands in north Queensland, Jane and her colleagues showed that female possums with access to the greatest amounts of available protein within their home ranges were more likely to breed twice, rather than just once per year.

Eucalypts are generally a poor source of protein and this is likely to limit populations of possums in natural bushland. However, given the abundance of high-quality food sources and limitless den sites in urban environments, it is not surprising that common brushtail possums seem to thrive there.

A possum in the roof!

People who share their homes with possums describe hearing them walking around the roof cavity. Emma’s research heard residents speak about the “thump, thump, thump” of possums walking across the ceiling. Others described being jolted awake at dawn to crashing and scraping sounds, and a feeling that someone was in the house. Some people admitted thinking their house was haunted, a feeling that was triggered by night-time noises coming from hidden spaces.

Hello, possum.
play4smee/Flickr, CC BY-NC

Many people enjoy living with possums, because they feel like it connects them to a time before Australia was urbanised. Some people also value personal connections with possums, becoming familiar with the individuals that share their garden – even giving them names and pointing them out to visitors.

However, people also often describe possums as a pest. They complain about the noise and damage that possums can cause. Damage to ceiling cavities, urine stains and odours in the ceiling are reported, and some people experience possums dying in the ceiling. These rotting bodies can be overwhelmingly smelly and extremely difficult to find.

It is interesting that many people both value possums and find them to be a pest. This is evidence of the complicated relationship that we have with native animals that live inside our homes. We enjoy their wildness, but are also challenged by the way that they make our homes a little bit less human and a little bit closer to nature.

Living well with common brushtail possums

Despite the fact that some people are less keen on house-sharing with possums, they are protected under the wildlife acts of most states in Australia. Although these laws vary, they generally require that residents seek a licence before trapping or moving a possum.

In New South Wales the relevant law is the National Parks and Wildlife Act 1974. If a possum is living in your ceiling, in NSW you can apply to the Office of Environment and Heritage (OEH) for a licence to trap it. Possums must be trapped humanely and released on the property where they were found within 150 m of the place where they were caught.

Note, however: possums moved outside of their home range typically die. They are also usually replaced within four weeks by another possum that moves into their territory.

The OEH suggests that people live alongside possums that share their garden, explaining that “if you encourage a possum to stay around and claim your yard as its territory, other possums will be discouraged from taking up residence”. The OEH also recommends installing nest boxes in trees away from the house to discourage possums from nesting in roofs, and carrying out repairs to close up any holes after possums are removed.

Wildlife protection laws mean that common brushtail possums have a right to live in urban Australia. This means that we need to learn to live well together.

This article is part of a series profiling our “hidden housemates”. Are you a researcher with an idea for a “hidden housemates” story? Get in touch.

The Conversation

Emma Power, Senior Research Fellow, Geography and Urban Studies, Western Sydney University and Jane DeGabriel, Research Fellow in Ecology, Hawkesbury Institute for the Environment, Western Sydney University

This article was originally published on The Conversation. Read the original article.

Nature’s hidden wealth is conservation’s missed opportunity


Andrew Beattie

Australia has one of the worst extinction records in the modern world. Since European settlement, a third of the country’s native mammals have disappeared. How can we stem the losses?

A recent article in Nature highlighted that most federal and state biodiversity conservation policy fails to recognise biodiversity as a major source of industrial products.

Much as explorers chart new territories, chemists, materials scientists, engineers and biologists are exploring biodiversity for medicine, agricultural and industrial products. This sits well with Australia’s current focus on innovation, driven by Prime Minister Malcolm Turnbull.

But the potential of biodiversity has been overlooked.

Inspiring nature

Animals and plants constitute a very small part of our native biodiversity (roughly 5%). The vast majority – fungi, bacteria and the enormous diversity of other microscopic organisms, including invertebrates – is a massive, largely unexplored economic resource.

The best known examples of commercial uses for biodiversity are the thousands of drugs secreted by bacteria and fungi. But others are examples of what is known as “bio-inspiration” and “bio-mimicry”, where wild species provide the blueprints for products.

While these products are of immense commercial value, the source species are rarely harvested in the conventional sense. Rather, a few specimens provide ample material for analysis.

So for microbes, invertebrates or plants, there is little concern that these industries are threats. For vertebrates, such as sharks, samples are either non-destructive or severely limited.

Some of the products such as spider silk and gecko feet are well known. But these are the tip of an iceberg.

Other innovations include fire detection inspired by charcoal beetles, clinical compounds from scorpions and leaping robots from locusts. In fact, bio-mimicry is huge in robotics, including the astonishing new field of “soft robots” modelled on tentacles, caterpillars and worms.

Robotics have taken inspiration from nature too.
Biomimetics and Dexterous Manipulation Laboratory, CC BY

Products such as drugs can be sourced from single-celled animals and plants and from microbes of all kinds, even those that are currently uncultivable. Super-water-repellent materials, are sourced from the outer surfaces of organisms as different as insects and higher plants.

Then there is bio-mineralization: soft-bodied animals make very hard substances, such as the radula of marine snails, a tongue tough enough to drill rock. To make materials that strong, industry currently requires high temperatures and pressures, not to mention polluting chemicals.

The snails make their radula and shell from natural materials and at normal temperatures and pressures. How do they do it? Many labs around the world are struggling to find out.

Why are these stories so important?

How can exploring biodiversity help conserve it?

First, much as charismatic animals such as tigers and whales are used as icons for conservation, so can species that we use for developing products – but with the added grunt that they are central to the economy. These are very sexy stories; fascinating tales of the transformation of natural phenomena into industrial products.

Australia’s Biodiversity Conservation Strategy states that we must “engage all Australians” to save biodiversity. But leaving out biodiversity and industrial products is a massive lost opportunity for engagement.

Second, as biodiversity products come from any kind of organism from any kind of ecosystem, these growing industries require the conservation of that resource. This would greatly expand the current conservation focus on a few charismatic species.

Third, much of biodiversity exploration research is overseas. Some Australian scientists and engineers are involved, for example, in utilising the arrangements of plant fibres to inspire lightweight strengthening of aircraft engines. However, it is hard to find the promotion of this exciting research in any policy nation-wide; political, economic or scientific.

Given Prime Minister Turnbull’s focus on innovation, and given that Australian biodiversity is both vast and unique, overlooking biomimicry and its related industries is another lost opportunity for both conservation and the national economy.

Scientists and engineers inside many industries are forging ahead with exploration for biodiversity products in many, non-destructive and highly imaginative ways all over the world.

It’s time our governments and conservationists wised up.

The Conversation

Andrew Beattie, Emeritus Professor

This article was originally published on The Conversation. Read the original article.

Amazon: Wildfires


The link below is to an article that looks at understory fires and the impact they are having on the Amazon.

For more visit:
http://www.mnn.com/earth-matters/wilderness-resources/stories/how-hidden-wildfires-are-destroying-the-amazon