Don’t worry about the huge Antarctic iceberg – worry about the glaciers behind it


Chen Zhao, University of Tasmania; Christopher Watson, University of Tasmania, and Matt King, University of Tasmania

Icebergs breaking off Antarctica, even massive ones, do not typically concern glaciologists. But the impending birth of a new massive iceberg could be more than business as usual for the frozen continent.

The Larsen C ice shelf, the fourth-largest in Antarctica, has attracted worldwide attention in the lead-up to calving an iceberg one-tenth of its area – or about half the area of greater Melbourne. It is still difficult to predict exactly when it will break free.

But it’s not the size of the iceberg that should be getting attention. Icebergs calve all the time, including the occasional very large one, with nothing to worry about. Icebergs have only a tiny direct effect on sea level.

The calving itself will simply be the birth of another big iceberg. But there is valid concern among scientists that the entire Larsen C ice shelf could become unstable, and eventually break up entirely, with knock-on effects that could take decades to play out.

Ice shelves essentially act as corks in a bottle. Glaciers flow from land towards the sea, and their ice is eventually absorbed into the ice shelf. Removal of the ice shelf causes glaciers to flow faster, increasing the rate at which ice moves from the land into the sea. This has a much larger effect on sea level than iceberg calving does.

While the prediction that Larsen C could become unstable is based partly on physics, it is also based on observations. Using aerial and satellite images, scientists have been able to track very similar ice shelves in the past, some of which have been seen to retreat and collapse.

The death of an ice shelf

The most dramatic ice shelf collapse observed so far is that of Larsen C’s neighbour to the north – the imaginatively named Larsen B. Over the course of just six weeks in 2002 the entire ice shelf splintered into dozens of icebergs. Almost immediately afterwards, the glaciers feeding into it sped up by two to six times. Those glaciers continue to flow faster to this day.

Satellite photo series of Larsen B Ice Shelf collapse from January 2002 to April 2002.
NASA

In our new study, published in Earth and Planetary Science Letters, we turn the clock back even further to look at the Wordie ice shelf, on the west coast of the southern Antarctic Peninsula, which began to retreat in the 1960s and eventually disappeared in January 2017.

Over the past 20 years, observations have shown that the main glacier feeding into the Wordie ice shelf, the Fleming Glacier, has sped up and thinned. Compared with the glaciers feeding Larsen B and C, Fleming Glacier is massive: 80km long, 12km wide, and 600m thick at its front.

Locations of the Larsen C Ice Shelf and the Wordie Ice Shelf-Fleming Glacier system with ice front positions from 1947 to 2016.
Author provided

We used historic aerial photographs from 1966 to create an elevation map of the Fleming Glacier, and compared it to elevation measurements from 2002 to 2015. Between 1966 and 2015 the Fleming Glacier thinned by at least 100m near the front. The thinning rate, which is the elevation change rate, rapidly increased: the thinning rate after 2008 is more than twice that during 2002 to 2008, and four times the average rates from 1966 to 2008.

Ice thinning rate of the Fleming Glacier region during (a) 2002-2008 and (b) 2008-2015.
Author provided

Ice flow speeds have also increased by more than 400m per year at the front since 2008. This is the largest speed change in recent years of any glacier in Antarctica. These changes all point to ice shelf collapse as the cause.

We estimate the total glacier ice volume lost from all glaciers that feed the Wordie is 179 cubic kilometres since 1966, or 319 times the volume of Sydney Harbour. The weight of this ice moving off the land and into the ocean has caused the bedrock beneath the glaciers to lift by more than 50mm.

Other research has suggested this lift could have acted to slow the glacier’s retreat, but it’s clear that the bedrock deformation has not stopped the ice movement speeding up. It seems the Fleming Glacier has a long way to go before it will return to a new stable state (in which snowfall feeding the glacier equals the ice flowing into the oceans).

Fifty years after the Wordie Ice Shelf began to collapse, the major feeding glaciers continue to thin and flow faster than before.

The ConversationWe can’t yet predict the full consequences of the new iceberg calving from Larsen C. But if the ice shelf does begin to retreat or collapse, history tells us it is very possible that its glaciers will flow faster – making yet more sea level rise inevitable.

Chen Zhao, PhD candidate of Antarctic Science, University of Tasmania; Christopher Watson, Senior Lecturer, Surveying and Spatial Sciences, School of Land and Food, University of Tasmania, and Matt King, Professor, Surveying & Spatial Sciences, School of Land and Food, University of Tasmania

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

The winners and losers of Antarctica’s great thaw



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Adélie penguin at the Mt Siple breeding colony, West Antarctica.
Jasmine Lee, Author provided

Jasmine Lee, The University of Queensland; Justine Shaw, The University of Queensland, and Richard Fuller, The University of Queensland

When you think of Antarctica, you probably picture vast, continuous ice sheets and glaciers, with maybe a penguin or two thrown in. Yet most Antarctic plants and animals live in the permanently ice-free areas that cover about 1% of the continent. Our new research predicts that these areas could grow by a quarter during this century, with mixed prospects for the species that currently live there.

Besides everyone’s favourite Emperor and Adélie penguins, terrestrial Antarctic species also include beautiful mosses, lichens, two types of flowering plants, and a suite of hardy invertebrates such as nematodes, springtails, rotifers and tardigrades, many of which are found nowhere else on Earth. Tardigrades – tiny creatures sometimes nicknamed “waterbears” – are so tough they can survive in space.

Antarctica’s ice-free areas are currently limited to a scattering of rocky outcrops along the coastline, or cliff faces, or the tops of mountain ranges. They form small patches of suitable habitat in a huge sea of ice, much like islands.

As a result, the plants and animals that live there are often isolated from each other. But as Antarctica’s climate warms, we expect ice-free areas to get bigger and eventually start joining up. This would create more habitat for native species, but also new opportunities for non-native species to spread.

Our study, published today in Nature, forecasts that climate change will expand Antarctica’s ice-free areas over the course of this century. Under the most severe scenario that we modelled (which is also the one on which the globe is currently tracking), more than 17,000 square km of new ice-free area could emerge across the continent by 2100.

This would increase the current total ice-free area by nearly a quarter. The majority of this new ice-free land will be on the Antarctic Peninsula, which could have three times as much ice-free area as it does today.

Projected Antarctic ice melt this century.
Lee et al. (2017) Nature

Brave new world

As the ice-free areas expand, the distances between them will decrease, giving plants and animals more opportunity to spread through the landscape. On the Antarctic Peninsula, which has already warmed more than anywhere else in Antarctica, many of the ice-free patches will expand so much that they will start joining together.

Will this increase in habitat availability benefit the plants and animals that live there? It will definitely provide new opportunities for some native plants and animals to expand their range and colonise new areas. The warming climate may also give a boost to species that are currently hampered by the lack of warmth, nutrients and water. Some Antarctic mosses, for example, are expected to grow faster as temperatures rise, and Antarctica’s two flowering plant species are already expanding southward.

However, the potential benefits seem likely to be outweighed by the negatives. The joining-up of habitat patches could allow species that have been isolated for much of their evolutionary past to meet suddenly. If the newcomers to a particular area outcompete the native species, then it may lead to localised extinctions. Over the coming centuries this could lead to the loss of many plants and animals, and the homogenisation of Antarctica’s ecosystems.

Antarctic aliens

An even bigger concern is that Antarctica’s great thaw could provide new opportunities for species to invade. Antarctica’s best bulwark against non-native species is its harsh climate and extreme weather, to which native Antarctic species have spent many thousands of years adapting.

A native Frisea springtail.
Melissa Houghton

We already know that many plants and invertebrates are reaching Antarctica, most often in food or cargo shipments. As the climate warms, some of these non-native species may be able to establish themselves on the Antarctic Peninsula, and the increasing connectivity will allow them to easily move through the landscape. Many of these animals and plants may become invasive, competing with the native species for space and resources.

We don’t know how Antarctica’s species will cope with the increasing competition. But if the sub-Antarctic islands provide any indication, the outlook is depressing. Australia’s World Heritage-listed Macquarie Island, for example, was severely impacted by invasive cats, rats, rabbits and mice (although it has since been declared free of these pests after an intensive eradication effort).

Several non-native species have already come to Antarctica, including the invasive annual meadowgrass Poa annua (a common weed around the world), which has colonised newly ice-free areas left behind by retreating glaciers. It is thought to outcompete Antarctica’s native plants, although we don’t yet know what the impact will be on animals.

Invasive meadowgrass on Macquarie Island.
Laura Williams

Humans – both scientists and tourists – are key transporters of non-native species to the continent, and tourist numbers continue to grow (almost 37,000 visited in the 2016-17 summer).

Biosecurity is paramount for the ongoing protection of Antarctica. If bags, shoes, clothes and field equipment are not properly cleaned and inspected before arriving on the continent, then non-native seeds, microbes and insects could be transported to Antarctica and begin to spread.

The ConversationWe call for protection of ice-free areas that will remain intact in a changing climate, and for the Antarctic scientific and tourism communities to pinpoint key areas where greater biosecurity and monitoring for invasive species may be needed.

Jasmine Lee, PhD candidate, biodiversity conservation and climate change, The University of Queensland; Justine Shaw, Conservation Biologist, The University of Queensland, and Richard Fuller, Associate Professor in Biodiversity and Conservation, The University of Queensland

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

Volcanoes under the ice: melting Antarctic ice could fight climate change



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Furious winds keep the McMurdo Dry Valleys in Anarctica free of snow and ice. Calcites found in the valleys have revealed the secrets of ancient subglacial volcanoes.
Stuart Rankin/Flickr, CC BY-NC

Silvia Frisia, University of Newcastle

Iron is not commonly famous for its role as a micronutrient for tiny organisms dwelling in the cold waters of polar oceans. But iron feeds plankton, which in turn hold carbon dioxide in their bodies. When they die, the creatures sink to the bottom of the sea, safely storing that carbon.

How exactly the iron gets to the Southern Ocean is hotly debated, but we do know that during the last ice age huge amounts of carbon were stored at the bottom of the Southern Ocean. Understanding how carbon comes to be stored in the depth of the oceans could help abate CO2 in the atmosphere, and Antarctica has a powerful role.

Icebergs and atmospheric dust are believed to have been the major sources of this micronutrient in the past. However, in research published in Nature Communications, my colleagues and I examined calcite crusts from Antarctica, and found that volcanoes under its glaciers were vital in delivering iron to the ocean during the last ice age.

Today, glacial meltwaters from Greenland and the Antarctic peninsula supply iron both in solution and as tiny particles (less than 0.0001mm in diameter), which are readily consumed by plankton. Where glaciers meet bedrock, minute organisms can live in pockets of relatively warm water. They are able to extract “food” from the rock, and in doing so release iron, which then can be carried by underwater rivers to the sea.

Volcanic eruptions under the ice can create underwater subglacial lakes, which, at times, discharge downstream large masses of water that travel to the ice margin and beyond, carrying with them iron in particle and in solution.

The role of melting ice in climate change is as yet poorly understood. It’s particularly pertinent as scientists predict the imminent collapse of part of the Larsen C ice shelf.

Researchers are also investigating how to reproduce natural iron fertilisation in the Southern Ocean and induce algal blooms. By interrogating the volcanic archive, we learn more about the effect that iron fertilisation from meltwater has on global temperatures.

A polished wafer of the subglacial calcites. The translucent, crystalline layers formed while in pockets of water, providing nourishment to microbes. The opaque calcite with rock fragments documents a period when waters discharged from a subglacial lake formed by a volcanic eruption, carrying away both iron in solution and particles of iron.
Supplied

The Last Glacial Maximum

During the Last Glacial Maximum, a period 27,000 to 17,000 years ago when glaciers were at their greatest extent worldwide, the amount of CO2 in the atmosphere was lowered to 180 parts per million (ppm) relative to pre-industrial levels (280 ppm).

Today we are at 400 ppm and, if current warming trends continue, a point of no return will be reached. The global temperature system will return to the age of the dinosaurs, when there was little difference in temperature from the equator to the poles.

If we are interested in providing a habitable planet for our descendants, we need to mitigate the quantity of carbon in the atmosphere. Blooms of plankton in the Southern Ocean boosted by iron fertilisation were one important ingredient in lowering CO2 in the Last Glacial Maximum, and they could help us today.

The Last Glacial Maximum had winds that spread dust from deserts and icebergs carrying small particles into the Southern Ocean, providing the necessary iron for algal blooms. These extreme conditions don’t exist today.

Hidden volcanoes

Neither dust nor icebergs alone, however, explain bursts of productivity recorded in ocean sediments in the Last Glacial Maximum. There was another ingredient, only discovered in rare archives of subglacial processes that could be precisely dated to the Last Glacial Maximum.

Loss of ice in Antartica’s Dry Valleys uncovered rusty-red crusts of calcite plastered on glacially polished rocks. The calcites have tiny layers that can be precisely dated by radiometric techniques.

A piece of subglacial calcite coating pebbles. This suggests that the current transporting the pebbles was quite fast, like a mountain stream. The pebbles were deposited at the same time as the opaque layer in the calcite formed.
Supplied

Each layer preserves in its chemistry and DNA a record of processes that contributed to delivering iron to the Southern Ocean. For example, fluorine-rich spherules indicate that underwater vents created by volcanic activity injected a rich mixture of minerals into the subglacial environment. This was confirmed by DNA data, revealing a thriving community of thermophiles – microorganisms that live in very hot water only.

Then, it became plausible to hypothesise that volcanic eruptions occurred subglacially and formed a subglacial lake, whose waters ran into an interconnected system of channels, ultimately reaching the ice margin. Meltwater drained iron from pockets created where ice met bedrock, which then reached the ocean – thus inducing algal blooms.

We dated this drainage activity to a period when dust flux does not match ocean productivity. Thus, our study indicates that volcanoes in Antarctica had a role in delivering iron to the Southern Ocean, and potentially contributed to lowering CO2 levels in the atmosphere.

The ConversationOur research helps explain how volcanoes act on climate change. But it also uncovers more about iron fertilisation as a possible way to mitigate global warming.

Silvia Frisia, Associate Professor, School of Environmental and Life Sciences , University of Newcastle

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

Climate shenanigans at the ends of the Earth: why has sea ice gone haywire?


Nerilie Abram, Australian National University

There is no doubt that 2016 has been a record-breaking year for Earth’s climate.

We will have to wait another couple of months for the final tally, but 2016 will be the hottest year in recorded history globally. Average temperatures are well above 1℃ warmer than a century ago.

Global average temperatures, and “global warming”, often give the impression of a gradual change in Earth’s climate occurring uniformly across the planet. This is far from the truth – particularly at the ends of the Earth. The Arctic and Antarctic are behaving very differently from the global picture.

One particular polar change that has caught the attention of scientists and the media this year has been the state of sea ice. The seasonal growth and decay of sea ice over the Arctic and Southern oceans is one of the most visible changes on Earth.

But in the past few months its seasonal progression has stalled, plunging Earth’s sea ice cover off the charts to the lowest levels on record for November. Explaining what has caused this unexpectedly dramatic downturn in sea ice is a tale of two poles.

Global sea ice area (including Antarctica and the Arctic) by year, 1977-2016. National Snow and Ice Data Centre.
Wipneus/NSIDC

Arctic amplifiers

The northern polar region is an epicentre for change in our warming world.

On average, the Arctic is warming at around twice the global average rate. This is due to several environmental processes in the Arctic that amplify the warming caused by rising atmospheric greenhouse gas levels.

One of these amplifiers is the sea ice itself.

As the climate warms, it’s no surprise that ice melts. What is less obvious is that when bright, white ice melts it is replaced with a dark surface (the ocean or land). Just as a black car parked in the sun will warm up faster than a white one, so the dark surface absorbs more heat from the sun than ice. This extra heat promotes more ice loss, and so the cycle goes.

This can explain the marked long-term decline of Arctic sea ice. But it can’t explain why the past month has seen such a sudden and dramatic change. For this we need to look to the weather.

Arctic climate is characterised by very large natural swings – so much so that in the past few weeks some regions of the Arctic have been a whopping 20℃ warmer than expected for this time of year.

The polar regions are separated from milder equatorial climates by a belt of westerly winds. In the northern hemisphere these winds are commonly referred to as the jet stream.

The strength of the jet stream is related to the north-to-south (cold-to-warm) gradient in northern hemisphere climate. The amplification of warming in the Arctic has reduced this gradient, and some scientists believe that this is allowing the northern jet stream to develop a more meandering path as it travels around the globe.

Jet stream winds in the northern hemisphere, November 11 2016.
Screenshot from Global Forecast System/National Centres for Environmental Information/US National Weather Service.

A weaving jet stream allows warm air to penetrate further northwards over the Arctic (the flip side is that extremely cold polar air can also be pulled south over the northern hemisphere continents, causing extreme cold snaps). This appears to be responsible for the current extremely warm temperatures over the Arctic Ocean, which have caused the normal advance of winter sea ice to stall.

In effect, what we are seeing in the Arctic is the combined effect of long-term climate change and an extreme short-term weather event (which itself is probably becoming more common because of climate change).

The southern story

It’s a different story when we look at the ocean-dominated southern hemisphere.

Antarctic climate records point to a delay in some of the effects of “global warming”. The reasons are still debated, partly because of the much shorter climate records that scientists have to work with in the Antarctic.

But it is likely that the expansive Southern Ocean is an important climate change dampener that is able to “hide” some of the extra heat being absorbed by our planet beneath the ocean surface where we don’t feel it – yet.

Unlike the dramatic declines in Arctic sea ice over recent decades, the sea ice that surrounds Antarctica has been increasing slightly over the past three-and-a-half decades and 2014 set records for the most extensive Antarctic sea ice on record. So the decline in Antarctic sea ice since August this year to record low levels has come as somewhat of a surprise.

Again, the weather may hold part of the answer.

The westerly winds that circle the Southern Ocean (analogous to the northern hemisphere’s jet stream) have strengthened and moved closer to Antarctica over the past few decades. One of the effects of this has been to push sea ice away from the Antarctic continent, making for a more expansive coverage across the surrounding ocean.

But the westerly winds are fickle. They are able to change their path across the Southern Ocean very quickly. And so while the southward march in their average position over many years is clear, predicting their behaviour from month to month remains difficult. This spring the westerly winds have tended to sit closer to Australia and out of reach of Antarctica’s sea ice.

What Antarctica’s sea ice will do in the future is still an open question. Climate models indicate that Antarctica won’t remain protected from global warming forever, but just if and when this might cause Antarctica’s sea ice to replicate the Arctic sea ice loss is still anyone’s guess.

Lessons in the madness

Extreme years, such as 2016, are important as they provide glimpses of what the new normal of our climate system may look like in the not-too-distant future.

But these pointers to where we are going also need to be assessed in terms of where we have come from. For sea ice, logbooks from the age of heroic exploration suggest that the Antarctic system is mostly still operating within its normal bounds.

The same cannot be said for the Arctic. The decline of sea ice there has been likened to a ball bouncing down a bumpy hill – some years it will bounce higher than others, but eventually the ball will reach the bottom.

When it does, the Arctic Ocean will be ice-free in summer. That’s a boon for shipping, but don’t expect to see any polar bears on those Arctic cruises.

The Conversation

Nerilie Abram, ARC Future Fellow, Research School of Earth Sciences; Associate Investigator for the ARC Centre of Excellence for Climate System Science, Australian National University

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

How China came in from the cold to help set up Antarctica’s vast new marine park


Nengye Liu, University of New England

Conservationists have been celebrating the creation of the world’s largest marine park, covering 1.55 million square kilometres of the Ross Sea off Antarctica.

The agreement, brokered at last week’s annual meeting of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) in Hobart, will enter into force on December 1, 2017 – thanks in large part to China ending its resistance to the proposal.

For the next 35 years, fishing will be totally banned in a “no-take zone” covering 1.12 million square kilometres (72%) of the marine park, with exceptions for krill and toothfish in specially designated research zones.

The marine park’s creation follows years of often frustrating negotiations. The United States and New Zealand brought the idea to the 2012 CCAMLR meeting, but were met with concerns, particularly from Russia and China.

At the 2014 meeting, China set out the reasons for its opposition. Its delegates argued that the term “conservation” should balance protection and rational use of marine living resources; that marine parks should not be set up in the Southern Ocean without convincing data showing they will work; and that the CCAMLR has already adopted a wide range of successful conservation measures in the seas around Antarctica.

A year later, China once again looked set to block the issue, posing a series of questions about the proposed marine park. How could marine parks allow rational use of marine living resources? How could they facilitate scientific research? How would they be monitored and regulated, and how long would the protections last?

Nevertheless, China surprisingly supported the Ross Sea proposal at the end of the 2015 CCAMLR meeting, paving the way for this month’s decision.

Why the turnaround from China’s previous opposition? And what does this mean for its growing and changing influence on Antarctic diplomacy?

Global influence

There are three key reasons that explain China’s shifting position. First, China is a latecomer to the current global ocean governance regime. When the Antarctic Treaty was signed in 1959, China was still relatively isolated from the international community. It was not until 1978 that it opened its doors to the world and engaged with the current international legal system, and as such it had little influence on the 1982 United Nations Convention on the Law of the Sea.

It has taken time for China to develop the necessary diplomatic and scientific expertise to become comfortable in this space. As a historic rule-taker rather than rule-maker, its government may need to overcome a natural mistrust of many existing regimes.

This issue is not unique to marine parks. Such hesitation was also evident when China joined the World Trade Organization in 2001 and when it started engaging with UN climate change negotiations in 1994. But China now uses the WTO dispute settlement body as frequently as other members, and ratified the Paris climate agreement at September’s G20 summit which it hosted for the first time – another sign of its increasing diplomatic engagement.

Second, China became a party of the CCAMLR in 2007. As the world’s second-largest economy and largest fishing nation, China has global fishing interests, including off Antarctica. Chinese Krill fishing in Antarctica has grown significantly since 2009, reaching 54,300 tonnes in 2014. This partly explains China’s concerns over proposed no-take zones.

There is, however, a deeper philosophical concern, which might be described as “anxiousness for commons”. While China’s Antarctic fishing interests account for only a very small share of its global catch, they are highly symbolic because Antarctic fishing showcases China’s quest for freedom in the “global commons”.

Third, the international community is currently developing a new global ocean governance regime. By coincidence, negotiations on the regulation of fishing in the Central Arctic Ocean and other international areas of the high seas have been going on at the same time as the discussions about the Ross Sea. In the Northeast Atlantic, the OSPAR has already established a network of high sea marine parks.

As a rising power, China would not be happy to face constraints or bans on its activities at a time when its rising status gives it access to places like the high seas, the ocean floor, the poles, and outer space. It would be a shame if China were to remain silent on those issues, and it probably won’t – China’s 13th Five Year Plan (2016-20) clearly says the nation would like to take a more active role in global ocean governance.

In the foreseeable future, we could possibly see China become more comfortable and active within the CCAMLR as well as the Antarctic Treaty System. Although generally being supportive, China would not keep silent. Rather, it would speak up more openly for its Antarctic interests, and have more intensive engagement with the Antarctic Treaty System.

One challenge for China would be how to enhance its capacity and expertise so as to provide high-quality proposals, which could not only pursue its own interests, but as an important global player, also help to make a concrete contribution to achieving sustainability in the Southern Ocean.

The Conversation

Nengye Liu, Senior Lecturer in Law, University of New England

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