I’ve heard the gravity changes when Antarctica melts will lower the seas around New Zealand. Will that save us from sea level rise?
The gravitational changes when Antarctica melts do indeed affect sea levels all over the world — but not enough to save New Zealand from rising seas.
The ice ages and their effects on sea level, geology, flora and fauna were topics of intense scientific and public interest all through the 19th century. Here’s how James Croll explained the “gravity effect” of melting ice in his 1875 book Climate and Time in their Geologic Relations:
Let us now consider the effect that this condition of things would have upon the level of the sea. It would evidently tend to produce an elevation of the sea-level on the northern hemisphere in two ways. First, the addition to the sea occasioned by the melting of the ice from off the Antarctic land would tend to raise the general level of the sea. Secondly, the removal of the ice would also tend to shift the earth’s centre of gravity to the north of its present position – and as the sea must shift along with the centre, a rise of the sea on the northern hemisphere would necessarily take place.
His back-of-the-envelope calculation suggested the effect on sea level from ice melting in Antarctica would be about a third bigger than average in the northern hemisphere and a third smaller in the south.
A more detailed mathematical study by Robert Woodward in 1888 has falling sea level as far as 2000km from Antarctica, but still rising by a third more than average in the north.
Woodward’s method is the basis of determining what is now called the “sea-level fingerprint” of melting ice. Two other factors also come into play.
The elasticity of the earth’s surface means the land will bounce up when it has less ice weighing it down. This pushes water away.
If the ice is not at the pole, its melting shifts the south pole (the axis of rotation), redistributing water.
Combining these effects gives the sea-level fingerprints of one metre of sea-level rise from either the West Antarctic Ice Sheet (WAIS) and Greenland (GIS), as shown here:
Woodward’s method from 1888 holds up pretty well – some locations in the northern hemisphere can get a third more than the average sea level rise. New Zealand gets a little bit below the average effect from Antarctica, and a little more than average from Greenland. Overall, New Zealand can expect slightly higher than average sea level rise.
Combining the sea-level fingerprints of all known sources of melting ice, together with other known changes of local land level such as subsidence and uplift, gives a good fit to the observed pattern of sea level rise around the world. For example, sea level has been falling near West Antarctica, due to the gravity effect.
Sea-level rise is accelerating, but the future rate is uncertain
The global average rise in sea level is 110mm for 1900-1993 and 100mm for 1993–2020. The recent acceleration is mostly due to increased thermal expansion of the top two kilometres of the oceans (warm water is less dense and expands) and increased melting of Greenland.
But the Gravity Recovery and Climate Experiment satellite has revealed the melting of Antarctica has accelerated by a factor of five in recent decades. Future changes in Antarctica represent a major source of uncertainty when trying to forecast sea levels.
Much of West Antarctica lies below sea level and is potentially subject to an instability in which warming ocean water melts the ice front from below. This would cause the ice sheet to peel off the ocean floor, accelerating the flow of the glacier towards the sea.
In fact, this has been directly observed, both in the location of glacial “grounding lines”, some of which have retreated by tens of kilometres in recent decades, and most recently by the Icefin submersible robot which visited the grounding line of the Thwaites Glacier, 2000km east of Scott Base, and found the water temperature to be 2℃ above the local freezing point.
The big question is whether this instability has been irreversibly set into motion. Some glaciologists say it has, but the balance of opinion, summarised by the IPCC’s report on the cryosphere, is that:
Observed grounding line retreat … is not definitive proof that Marine Ice Sheet Instability is underway. Whether unstable West Antarctic Ice Sheet retreat has begun or is imminent remains a critical uncertainty.
The IPCC special report on 1.5℃ concluded that “these instabilities could be triggered at around 1.5℃ to 2℃ of global warming”.
What’s in store for New Zealand
Predictions for New Zealand range from a further 0.46 metres of sea-level rise by 2100 (under a low-emission scenario, with warming kept under 2℃) to 1.05 metres (under a high-emission scenario).
A continued rise in sea levels over future centuries may be inevitable — there are 66m of sea level rise locked up in ice at present — but the rate will depend on how fast we can reduce emissions.
A five-year, NZ$7m research project, NZ SeaRise, is now underway, seeking to improve predictions of sea-level rise out to 2100 and beyond and their implications for local planning.
Eric Jorden Raes, Dalhousie UniversityAboard an Australian research vessel, the RV Investigator, we sailed for 63 days from Antarctica’s ice edge to the warm equator in the South Pacific and collected 387 water samples.
Our goal? To determine how the genetic code of thousands of different micro-organisms can provide insights into the ocean’s functional diversity — the range of tasks performed by bacteria in the ocean.
Our research was published yesterday in Nature Communications. It showed how bacteria can help us measure shifts in energy production at the base of the food web. These results are important, as they highlight an emerging opportunity to use genetic data for large-scale ecosystem assessments in different marine environments.
In light of our rapidly changing climate, this kind of information is critical, as it will allow us to unpack the complexity of nature step by step. Ultimately, it will help us mitigate human pressures to protect and restore our precious marine ecosystems.
Why should we care about marine bacteria?
The oceans cover 71% of our planet and sustain life on Earth. In the upper 100 meters, the sunlit part of the oceans, microscopic life is abundant. In fact, it’s responsible for producing up to 50% of all the oxygen in the world.
But the role of bacteria go beyond oxygen production. Bacteria sustain, inject and control the fluxes of energy, nutrients and organic matter in our oceans. They provide the energy and food for the entire marine food web, from tiny crustaceans to fish larvae, whales and the fish we eat.
These micro-organisms also execute key roles in numerous biogeochemical cycles (the carbon, nitrogen, phosphorus, sulphur and iron cycles, to name a few).
So, it’s important to quantify their various tasks and understand how the different bacterial species and their functions respond to environmental changes.
Global ocean research initiatives — such as GO-SHIP and GEOTRACES — have been measuring the state of oceans in expeditions like ours for decades. They survey temperature, salinity, nutrients, trace metals (iron, cobalt and more) and other essential ocean variables.
Only recently, however, have these programs begun measuring biological variables, such as bacterial gene data, in their global sampling expeditions.
Including bacterial gene data to measure the state of the ocean means we can try to fill critical knowledge gaps about how the diversity of bacteria impacts their various tasks. One hypothesis is whether a greater diversity of bacteria leads to a better resilience in an ecosystem, allowing it to withstand the effects of climate change.
In our paper, we addressed a fundamental question in this global field of marine microbial ecology: what is the relationship between bacterial identity and function? In other words, who is doing what?
What we found
We showed it’s possible to link the genetic code of marine bacteria to the various functions and tasks they execute, and to quantify how these functions changed from Antarctica to the equator.
The functions that changed include taking in carbon dioxide from the atmosphere, bacterial growth, strategies to cope with limited nutrients, and breaking down organic matter.
Another key finding is that “oceanographic fronts” can act as boundaries within a seemingly uniform ocean, resulting in unique assemblages of bacteria with specific tasks. Oceanographic fronts are distinct water masses defined by, for instance, sharp changes in temperature and salinity. Where the waters meet and mix, there’s high turbulence.
The change we recorded in energy production across the subtropical front, which separates the colder waters from the Southern Ocean from the warmer waters in the tropics, was a clear example of how oceanographic fronts influenced bacterial functions in the ocean.
Tracking changes in our ecosystems
As a result of our research, scientists may start using the functional diversity of bacteria as an indicator to track changes in our ecosystems, like canaries in a coal mine.
So the functional diversity of bacteria can be used to measure how human growth and urbanisation impact coastal areas and estuaries.
For example, we can more accurately and holistically measure the environmental footprint of aquaculture pens, which are known to affect water quality by increasing concentrations of nutrients such as carbon, nitrogen and phosphorus – all favourite elements utilised by bacteria.
Likewise, we can track changes in the environmental services rendered by estuaries, such as their important role in removing excessive nitrogen that enters the waterways due to agriculture run-off and urban waste.
With 44% of the world’s population living along coastlines, the input of nitrogen to marine ecosystems, including estuaries, is predicted to increase, putting a strain on the marine life there.
Ultimately, interrogating the bacterial diversity using gene data, along with the opportunity to predict what this microscopic life is or will be doing in future, will help us better understand nature’s complex interactions that sustain life in our oceans.
In December, Antarctica lost its status as the last continent free of COVID-19 when 36 people at the Chilean Bernardo O’Higgins research station tested positive. The station’s isolation from other bases and fewer researchers in the continent means the outbreak is now likely contained.
However, we know all too well how unpredictable — and pervasive — the virus can be. And while there’s currently less risk for humans in Antarctica, the potential for the COVID-19 virus to jump to Antarctica’s unique and already vulnerable wildlife has scientists extremely concerned.
We’re among a global team of 15 scientists who assessed the risks of the COVID-19 virus to Antarctic wildlife, and the pathways the virus could take into the fragile ecosystem. Antarctic wildlife haven’t yet been tested for the COVID-19 virus, and if it does make its way into these charismatic animals, we don’t know how it could affect them or the continent’s ecosystem stability.
Jumping from animals to humans, and back to animals
The COVID-19 virus is one of seven coronaviruses found in people — all have animal origins (dubbed “zoonoses”), and vary in their ability to infect different hosts. The COVID-19 virus is thought to have originated in an animal and spread to people through an unknown intermediate host, while the SARS outbreak of 2002-2004 likely came from raccoon dogs or civets.
Given the general ubiquity of coronaviruses and the rapid saturation of the global environment with the COVID-19 virus, it’s paramount we explore the risk for it to spread from people to other animals, known as “reverse zoonoses”.
The World Organisation for Animal Health is monitoring cases of the COVID-19 virus in animals. To date, only a few species around the globe have been found to be susceptible, including mink, felines (such as lions, tigers and cats), dogs and a ferret.
Whether the animal gets sick and recovers depends on the species. For example, researchers found infected adolescent cats got sick but could fight off the virus, while dogs were much more resistant.
While mink, dogs or cats are not in Antarctica, more than 100 million flying seabirds, 45% of the world’s penguin species, 50% of the world’s seal populations and 17% of the world’s whale and dolphin species inhabit the continent.
In a 2020 study, researchers ran computer simulations and found cetaceans — whales, dolphins or porpoises — have a high susceptibility of infection from the virus, based on the makeup of their genetic receptors to the virus. Seals and birds had a lower risk of infection.
We concluded that direct contact with people poses the greatest risk for spreading the virus to wildlife, with researchers more likely vectors than tourists. Researchers have closer contact with wildlife: many Antarctic species are found near research stations, and wildlife studies often require direct handling and close proximity to animals.
Tourists, however, are still a concerning vector, as they visit penguin roosts and seal haul-out sites (where seals rest or breed) in large numbers. For instance, a staggering 73,991 tourists travelled to the continent between October 2019 and April 2020, when COVID-19 was just emerging.
Each visitor to Antarctica carries millions of microbial passengers, such as bacteria, and many of these microbes are left behind when the visitors leave. Most are likely benign and probably die off. But if the pandemic has taught us anything, it takes only one powerful organism to jump hosts to cause a pandemic.
How to protect Antarctic wildlife
There are guidelines for visitors to reduce the risk of introducing infectious microbes. This includes cleaning clothes and equipment before heading to Antarctica and between animal colonies, and keeping at least five metres away from animals.
These rules are no longer enough in COVID times, and more measures must be taken.
The first and most crucial step to protect Antarctic wildlife is controlling human-to-human spread, particularly at research stations. Everyone heading to Antarctica should be tested and quarantined prior to travelling, with regular ongoing tests throughout the season. The fewer people with COVID-19 in Antarctica, the less opportunity the virus has to jump to animal hosts.
Second, close contact with wildlife should be restricted to essential scientific purposes only. All handling procedures should be re-evaluated, given how much we just don’t know about the virus.
We recommend all scientific personnel wear appropriate protective equipment (including masks) at all times when handling, or in close proximity to, Antarctic wildlife. Similar recommendations are in place for those working with wildlife in Australia.
Migrating animals that may have picked up COVID-19 from other parts of the world could also spread it to other wildlife in Antarctica. Skuas, for example, migrate to Antarctica from the South American coast, where there are enormous cases of COVID-19.
And then there’s the issue of sewage. Around 37% of bases release untreated sewage directly into the Antarctic ecosystem. Meanwhile, an estimated 57,000 to 114,000 litres of sewage per day is dumped from ships into the Southern Ocean.
Fragments of the COVID virus can be found in wastewater, but these fragments aren’t infectious, so sewage isn’t considered a transmission risk. However, there are other potentially dangerous microbes found in sewage that could be spread to animals, such as antibiotic-resistant bacteria.
We can curb the general risk of microbes from sewage if the Antarctic Treaty formally recognises microbes as invasive species and a threat to the Antarctic ecosystem. This would support better biosecurity practices and environmental control of waste.
In these early stages of the pandemic, scientists are scrambling to understand complexity of COVID-19 and the virus’s characteristics. Meanwhile, the virus continues to evolve.
Until the true risk of cross-species transmission is known, precautions must be taken to reduce the risk of spread to all wildlife. We don’t want to see the human footprint becoming an epidemic among Antarctic wildlife, a scenario that can be mitigated by better processes and behaviours.
Two-thirds of the world’s oceans fall outside national jurisdictions – they belong to no one and everyone.
These international waters, known as the high seas, harbour a plethora of natural resources and millions of unique marine species.
But they are being damaged irretrievably. Research shows unsustainable fisheries are one of the greatest threats to marine biodiversity in the high seas.
According to a 2019 global assessment report on biodiversity and ecosystem services, 66% of the world’s oceans are experiencing detrimental and increasing cumulative impacts from human activities.
In the high seas, human activities are regulated by a patchwork of international legal agreements under the 1982 UN Convention on the Law of the Sea (UNCLOS). But this piecemeal approach is failing to safeguard the ecosystems we depend on.
A decade ago, world leaders updated an earlier pledge to establish a network of marine protected areas (MPAs) with a mandate to protect 10% of the world’s oceans by 2020.
But MPAs cover only 7.66% of the ocean across the globe. Most protected sites are in national waters where it’s easy to implement and manage protection under the provision of a single country.
In the more remote areas of the high seas, only 1.18% of marine ecosystems have been gifted sanctuary.
The Southern Ocean accounts for a large portion of this meagre percentage, hosting two MPAs. The South Orkney Islands southern shelf MPA covers 94,000 square kilometres, while the Ross Sea region MPA stretches across more than 2 million square kilometres, making it the largest in the world.
The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is responsible for this achievement. Unlike other international fisheries management bodies, the commission’s legal convention allows for the closing of marine areas for conservation purposes.
A comparable mandate for MPAs in other areas of the high seas has been nowhere in sight — until now.
In 2017, the UN started negotiations towards a new comprehensive international treaty for the high seas. The treaty aims to improve the conservation and sustainable use of marine organisms in areas beyond national jurisdiction. It would also implement a global legal mechanism to establish MPAs in international waters.
This innovative international agreement provides an opportunity to work across institutional boundaries towards comprehensive high seas governance and protection. It is crucial to use lessons drawn from existing high seas marine protection initiatives, such as those in the Southern Ocean, to inform the treaty’s development.
The final round of treaty negotiations is pending, delayed by the COVID-19 pandemic, and significant detail within the treaty’s draft text remains undeveloped and open for further debate.
Lessons from Southern Ocean management
CCAMLR comprises 26 member states (including the European Union) and meets annually to make conservation-based decisions by unanimous consensus. In 2002, the commission committed to establishing a representative network of MPAs in Antarctica in alignment with globally agreed targets for the world’s oceans.
The two established MPAs in the high seas are far from an ecologically representative network of protection. In October 2020, the commission continued negotiations for three additional MPAs, which would meet the 10% target for the Southern Ocean, if agreed.
But not a single proposal was agreed. For one of the proposals, the East Antarctic MPA, this marks the eighth year of failed negotiations.
CCAMLR’s progress towards its commitment for a representative MPA network may have ground to a halt, but the commission has gained invaluable knowledge about the challenges in establishing MPAs in international waters. CCAMLR has demonstrated that with an effective convention and legal framework, MPAs in the high seas are possible.
The commission understands the extent to which robust scientific information must inform MPA proposals and how to navigate inevitable trade-offs between conservation and economic interests. Such knowledge is important for the UN treaty process.
As the high seas treaty moves closer to adoption, it stands to outpace the commission regarding progress towards improved marine conservation. Already, researchers have identified high-priority areas for protection in the high seas, including in Antarctica.
Many species cross the Southern Ocean boundary into other regions. This makes it even more important for CCAMLR to integrate its management across regional fisheries organisations – and the new treaty could facilitate this engagement.
But the window of time is closing with only one round of negotiation left for the UN treaty. Research tells us Antarctic decision-makers need to use the opportunity to ensure the treaty supports marine protection commitments.
Stronger Antarctic leadership is urgently needed to safeguard the Southern Ocean — and beyond.
In 2018, a map named after an oceanographer went viral.
The so-called Spilhaus projection, in which Earth is viewed from above the South Pole, was designed to show the connected nature of the ocean basins.
It is a perspective that comes naturally to those who live in the ocean-dominated southern hemisphere.
The Southern Ocean, also called the Antarctic Ocean (or even the Austral ocean), is like no other and best described in superlatives.
Storing heat and carbon
Let’s first look at the Southern Ocean’s capacity to store excess heat and carbon. The world’s oceans take up more than 90% of the excess heat generated by the burning of fossil fuels and a third of the additional carbon dioxide.
The Southern Ocean, south of 30°S, is estimated to store about 75% of this global oceanic uptake of excess heat and about 35% of the global uptake of excess carbon from the atmosphere. It is the primary storage of heat and carbon for the planet.
The Southern Ocean connects all major ocean basins, except the Arctic. The link is the Antarctic Circumpolar Current (ACC) – the largest ocean current on the planet. It carries more than 100 times the flow of all the rivers on Earth and transports enough water to fill Lake Ontario in just a few hours.
A combination of strong winds and a nearly uninterrupted passage around Antarctica give the ACC its strong flows and speed.
The Roaring Forties, Furious Fifties and Screaming Sixties are all popular names for the strong westerly winds that blow, nearly uninterrupted, across the Southern Ocean, creating equally impressive waves. This results in a massively energetic – and hard to measure – ocean surface.
But the heat and carbon exchanges across this complicated interface are globally important, and oceanographers have designed tools specifically for this challenging environment.
To really comprehend the Southern Ocean, one must think in three dimensions. Waters with different properties mix both horizontally and vertically in eddies.
Relatively warm subtropical water is mixed south, deep cool water from the North Atlantic rises back up toward the surface and colder polar water masses mix northward and sink back down.
This complex interplay is guided by the wind and by the shape of the seafloor.
To the north, there are only three major constrictions: the 850km-wide Drake Passage, and the submarine Kerguelan and Campbell Plateaus. To the south, the ACC butts up against Antarctica.
Here the ocean plays another crucial role in the global climate system by bringing relatively warm — and warming — Circumpolar Deep Water into contact with the ice fringing Antarctica.
Annual thaw and freeze of sea ice
The annual cycle of sea ice growing and melting around Antarctica is one of the defining rhythms of our planet and an important facet of the Southern Ocean. The two polar regions couldn’t be more different in this regard.
The Arctic is a small, deep ocean surrounded by land with only narrow exits. The Antarctic is a large landmass with a continental shelf surrounded by ocean. Each year, 15 million square kilometres of sea ice advance and retreat in these waters.
In contrast to the clear and dramatic changes in the north, the rhythm of Antarctic sea ice has followed less obvious patterns. In the face of a warming ocean, it was actually slowly expanding northward until around 2016, when it suddenly started to contract.
Looking at the annual cycle of Antarctic sea ice, one might think it simply grows and melts in place as things get cold and warmer through the year. But in truth, much of the sea ice production happens in polynya – sea ice factories near the coast where cold and fast Antarctic winds both create and blow away new sea ice as fast as it appears.
This process brings us back to global ocean circulation. When the new ice grows, the salt from the freezing sea water gets squeezed out and mixes with the seawater below, creating colder and saltier seawater that sinks to the seafloor and drains northward.
Polynya are in effect a metro stop on a global transport system that sees water sinking at the poles, flowing north to be mixed upwards in a cycle lasting close to 1,000 years.
Not all ice shelves respond the same
Computer simulations have shown how the ice shelves at Antarctica’s fringe have waxed and waned over past millennia.
Because these floating extensions of the ice sheet interact directly with the ocean, they make the ice sheet sensitive to climate. Ocean warming and changes in the source of the water coming into contact with an ice shelf can cause it – and in turn the whole ice sheet – to change.
But not all ice shelves will respond to warming in the same way. Some ocean cavities are cold and slowly evolving. Others are actually described as hot – in polar terms – because of their interaction with Circumpolar Deep Water. The latter are changing rapidly right now.
We can observe many cryosphere processes from space, but to truly understand how far the ocean reaches beneath the ice we have to go hundreds of metres beneath the ice surface.
Making climate predictions requires an understanding of detailed processes that happen on short timescales, such as tidal cycles, in parts of the planet we are only beginning to explore.
How do we sample something so big and so stormy? With robots.
Satellites have been observing the ocean surface since the 1980s. This technology can measure properties such as temperature and ocean surface height, and even be used to estimate biological productivity. But satellites can’t see beneath the surface.
When the game-changing Argo programme started in the 1990s, it revolutionised earth science by building a network of drifting ocean sentinels measuring temperature and salinity down to a depth of two kilometres.
The research vessel Kaharoa holds the record for the most deployments of Argo probes in the Southern Ocean, including its most recent storm-tossed, COVID-19-impacted voyage south of Australia and into the Indian Ocean.
The Argo program is only the start of a new era of ocean observation. Deep Argo probes dive to depths of 6km to detect how far down ocean warming is penetrating.
The past and future Southern Ocean
Earth hasn’t always looked as it does today. At times in the planet’s past, the Southern Ocean didn’t even exist. Continents and ocean basins were in different positions and the climate system operated very differently.
From the narrow view of human evolution, the Southern Ocean has been a stable component of a climate system and subject to relatively benign glacial oscillations. But glacial cycles play out over tens of thousands of years.
We are imposing a very rapid climate transient. The nearly three centuries since the start of the industrial revolution is shorter than the blink of an eye in geological context.
Future changes in the short (say by 2050) and long (by 2300) term are difficult to project. While the physics are relatively clear about what will happen, predicting when it will happen is more challenging.
Simulation tools that get the ocean, atmosphere and ice processes right are only starting to include ice shelf cavities and ocean eddies. The most recent synthesis of climate models shows progress in the simulated workings of the Southern Ocean. But sea ice remains a challenge to simulate well.
This is the frontier: a global research community working to connect data with rapidly improving computer models to better understand how this unique ocean operates.
Life in a sub-zero ocean
At first glance, Antarctica seems an inhospitable and almost barren environment of ice and snow, speckled with occasional seabirds and seals.
But diving beneath the surface reveals an ocean bursting with life and complex ecosystems, from single-celled algae and tiny spineless creatures to the well-known top predators: penguins, seals and whales.
It’s not easy to study life in the Southern Ocean. Waves can be more than 20 metres high, and icebergs and sea ice lurk among them.
The water temperature is often sub-zero – freshwater freezes at 0℃, but saltwater freezes at closer to -2℃. Although scuba diving is possible, a lot of research on life in the Southern Ocean is done through remote sampling.
Marine scientists use robotic tools such as remotely operated underwater vehicles to look at and collect samples, and grabs and dredges to bring up bottom-dwelling organisms. We take genetic samples from marine mammals by shooting tiny biopsy tubes (like needles), attached to a cord for retrieval, into the animal’s flesh from a distance.
We can glean wider information on diversity from environmental DNA (eDNA). Traces of organisms are filtered from samples of water and analysed using genetic tools that can usually identify what sorts of species are or were present.
Every expedition reveals new species – some of which are potentially commercially valuable, and all of which are important parts of the Southern Ocean ecosystem. Our knowledge of the diversity of the region is growing rapidly.
Nonetheless, the Southern Ocean is vast, and much of it remains either unsampled or undersampled.
Down at the bottom of the food chain
In the Southern Ocean, primary producers (organisms at the start of the food chain) range from single-celled algae – such as diatoms with intricately detailed shells made of silica – through to large macroalgae like kelp.
Kelp and other large seaweeds generally only survive where icebergs don’t often scrape the seafloor. Diatoms are diverse, and some species thrive on the underside of sea ice.
Ice algae form an important food source for krill, small crustaceans that are a critical part of Southern Ocean food webs.
Astonishingly, the cold Southern Ocean is also home to hot hydrothermal vent systems. These communities, which include huge densities of crustaceans and echinoderms, get their energy from chemicals that seep out of Earth’s crust, rather than from the Sun.
Antarctic invertebrates make up more than 90% of the species in the Southern Ocean. More than 50% are unique to this ocean.
These invertebrates are often much larger than their relatives in more northern, warmer waters. This phenomenon is know as “polar gigantism” and is found across many groups, with giant sea spiders, huge sponges and scale worms the size of a forearm.
Nobody is quite sure why Antarctic invertebrates grow so large, but it may be related to high oxygen levels, slow growth rates or the absence of key predatory groups such as sharks and brachyuran crabs.
Higher up in the food chain
In the marine food chain, Antarctic krill swim between the algal primary producers and the iconic top predators we always associate with Antarctica.
Baleen whales get much of their energy from great gulps of swarming krill (10,000–30,000 individual animals per cubic metre), and the pink streaks in penguin and seal poo show they are also keen on these tasty crustaceans.
Fish and cephalopods (squid and octopus) thrive in the Southern Ocean, providing food for deep-diving marine mammals such as elephant seals. Some fish species are so well adapted to the oxygen-rich cold waters they no longer produce red blood cells but instead produce antifreeze proteins in their blood to help them survive in the subzero waters.
Protecting marine environments
Arguably the most voracious predators in the Southern Ocean are humans.
Antarctica might be remote, but in the 200 or so years since its discovery, the seas around Antarctica have been heavily exploited by people.
First came the sealers, then the whalers, driving species to the brink of extinction. Even penguins were harvested for their oil.
More recently, fish and krill (which is fished for food or dietary supplements) have been the main targets, and populations of some species have declined sharply as a consequence.
When more indirect impacts like ocean warming and acidification combine with fishing, this can lead to declining populations of krill, which in turn leads to reduced numbers of top predators such as whales.
Fishing in the Southern Ocean can be hard to regulate because these waters do not belong to any one nation. To help manage the impact of fisheries, quotas that limit catches are now managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).
This international body is also working to establish more marine protected areas.
Without these efforts to manage catches, critical parts of the food web (such as krill) could be exploited to such an extent that ecosystems could collapse.
Changing environments mean changing ecosystems
More than 21,000 tourists and scientists visit Antarctica each year, potentially bringing pollution, diseases and invasive species. To manage human impacts on Antarctic ecosystems, and to help with political negotiations, the Antarctic Treaty came into force on June 23, 1961.
The impacts of global climate change and ocean acidification are nonetheless evident in the Southern Ocean, with warming ocean temperatures, reduction in sea ice and collapsing ice shelves.
Increasingly, research is showing that even the distant Southern Ocean is not truly cut off from the rest of the world, with warming, plastic pollution and non-native species making their way to Antarctic waters from beyond the mighty polar front.
Rafts of floating seaweeds from outside the Antarctic, some carrying animal passengers, are able to cross the Southern Ocean and reach Antarctic shores. At the moment, they don’t seem able to survive the extreme climate of Antarctica, but that could change with warming.
New species moving in and setting up shop will put a lot of pressure on Antarctica’s unique plants and animals.
It’s not all doom and gloom, though. Over the several decades since the Antarctic Treaty came into force, we’ve seen that nations can work together to help resolve challenges facing the Antarctic. One example is the establishment of Antarctic Marine Protected Areas (MPAs).
This level of international cooperation should give us hope not just for the future of the Southern Ocean, but also for other key challenges the world faces.
Five profiles open our series on the global ocean, delving into ancient Indian Ocean trade networks, Pacific plastic pollution, Arctic light and life, Atlantic fisheries and the Southern Ocean’s impact on global climate. All brought to you from The Conversation’s international network.
Antarctica Day celebrates the icy continent and its unique governance system. It’s the anniversary of the Antarctic Treaty’s adoption on December 1 1959. Framed in a spirit of global co-operation, the treaty acknowledges Antarctica does not belong to any one country. Article IV states:
No acts or activities taking place while the present Treaty is in force shall constitute a basis for asserting, supporting or denying a claim to territorial sovereignty in Antarctica or create any rights of sovereignty in Antarctica.
These five cities on the Southern Ocean rim — Cape Town, Christchurch, Hobart, Punta Arenas and Ushuaia — share a unique interest in Antarctica and an opportunity to shape its future.
How do their residents feel about Antarctica?
Our survey of 1,659 residents of these cities in July this year found they care deeply about the icy continent. Overall, and for many particular groups, environmental care greatly outweighs economic interests. Many residents express hope that this care might translate into more protective policies and action.
However, emotions were mixed, with pessimism and sadness also common responses. When we asked people how they feel about “the future of Antarctica in the next 20 years”, “hope” took first place, followed closely by “pessimism” and “sadness”.
The survey is part of the Antarctic Cities Project, which finishes this month. For the past four years an international team of researchers, city officials, national Antarctic programs and youth groups have worked together to develop a framework to strengthen Antarctic connections and a sense of guardianship for the continent. The framework encompasses the cities’ own urban sustainability strategies within a wider concern for the planet.
Our work focuses on shifting from the limited idea of “gateway” to this broader sense of becoming Antarctic “custodial cities”.
Our online survey of the cities’ residents over the age of 18 asked:
how informed they felt about the relationship between their city and Antarctica
their opinion on how important Antarctica is to their city’s identity
how responsible they, their families and friends think they are for the future of Antarctica.
We posed the question: “Why is it important for your city to develop an identity in relation to Antarctica?” The response “it drives us to take care of the environment” was most common (57%) across all five cities. Other responses included:
“it creates a unique brand for our cities” (36%)
“it creates more jobs” (32%)
“it attracts more tourists” (31%)
“it reinforces residents’ attachment to place” (29%).
Caring for the environment was the most selected option for all ages. Women felt this particularly strongly. Men favoured the more economically oriented options, “it generates more jobs” and “it attracts more tourists”.
Women and people between the ages of 31 and 40 reported higher levels of “hope” and lower levels of “indifference”. Indifference was higher among people between 18 and 30, reaching 16.42%. In this age group, and with men overall, “pessimism” significantly outweighed “hope”. Punta Arenas and Ushuaia residents expressed more “hope” than in other cities.
Young people’s expressions of pessimism and indifference bear witness to the urgent work of reforming our relationship to the Antarctic region. They will be the beneficiaries, and increasingly the drivers, of this reform.
A decade of co-operative custodianship
The cities first came together with the 2009 signing in Christchurch of a statement of intent to promote peaceful co-operation. Though it expired 18 months later, various city and national government policies have reinforced the five cities’ “Antarctic gateway” status. They have put forward visions for enhancing and capitalising on their Antarctic identities, a key part of their relationship to the world.
In an example of action at a local level, the City of Christchurch is moving towards a custodianship model by basing its 2018 Antarctic strategy on two key principles:
embracing the Maori principle of Kaitiakitanga –
meaning guardianship, protection, preservation or sheltering –
and a customary way of caring for the environment based on traditional Māori world view to guide the city’s involvement in the region
taking a leadership role in sustainable actions for the benefit of the Antarctic region and the city.
In coming together, the five cities are showing they can play an important role in defining how Antarctica is imagined, how discourse is framed and how the continent is vicariously experienced.
The Antarctic Cities Project has created an interlinked network of organisations that can learn from and benefit each other. This network of local government, national Antarctic programs, youth groups and polar organisations has produced Antarctic Futures, an educational online serious game.
During 2020 we began work on a Charter of Principles for Antarctic Cities in collaboration with the Hobart and Christchurch city councils. It draws from Christchurch’s 2018 Antarctic Gateway Strategy and the 2017 Tasmanian Antarctic Gateway Strategy. This charter will guide sustainable urban practice and embrace Antarctica’s significance to the economies of these cities while charting ways forward for sustainable development.
The charter aims to celebrate the unique polar heritage of these cities and emphasises the crucial role of youth organisations for engaging with the future of Antarctica. And it acknowledges that human connections with Antarctica extend well beyond the last two centuries, embracing Indigenous conceptions of caring for Country, both land and water.
In the Anthropocene, global public consciousness of, and responsibility for, the icy continent in a time of climate change is increasing. These cities’ relationship with the region to their south and to each other is a valuable part of their urban identity and Antarctica’s future – something worth celebrating on Antarctica Day.
The Western Antarctic Peninsula, the northernmost part of the continent and one of its most biodiverse regions, is particularly vulnerable. It faces the cumulative threats of commercial krill fishing, tourism, research infrastructure expansion and climate change.
In an article published in Nature today, we join more than 280 women in STEMM (science, technology, engineering, maths and medicine) from the global leadership initiative Homeward Bound to call for the immediate protection of the peninsula’s marine environment, through the designation of a marine protected area.
Our call comes ahead of a meeting, due in the next fortnight, of the international group responsible for establishing marine protected areas in the Southern Ocean. We urge the group to protect the region, because delays could be disastrous.
Threats on the peninsula
The Southern Ocean plays a vital role in global food availability and security, regulates the planet’s climate and drives global ocean currents. Ice covering the continent stores 70% of the earth’s freshwater.
Climate change threatens to unravel the Southern Ocean ecosystem as species superbly adapted to the cold struggle to adapt to warmer temperatures. The impacts of climate change are especially insidious on the Western Antarctic Peninsula, one of the fastest-warming places on Earth. In February, temperatures reached a record high: a balmy 20.75℃.
Tourist numbers have doubled in the past decade, increasing the risk of introducing invasive species that hitch a ride on the toursts’ gear. More than 74,000 cruise ship passengers visited last year, up from 33,000 in the 2009-10 season.
The expansion of infrastructure to accommodate scientists and research, such as buildings, roads, fuel storage and runways, can also pose a threat, as it displaces local Antarctic biodiversity.
Eighteen nations have science facilities on the Antarctic Peninsula, the highest concentration of research stations anywhere on the continent. There are 19 permanent and 30 seasonal research bases there.
An MPA around the peninsula was first proposed in 2018, covering 670,000 square kilometres. But the Commission for the Conservation of Antarctic Marine Living Resources (the organisation responsible for establishing MPAs in the Southern Ocean) has yet to reach agreement on it.
The proposed MPA is an excellent example of balancing environmental protection with commercial interests.
The area would be split into two zones. The first is a general protection zone covering 60% of the MPA, designed to protect different habitats and key wildlife and mitigate specific ecosystem threats from fishing.
The second is a krill fishery zone, allowing for a precautionary management approach to commercial fishing and keeping some fishing areas open for access.
The proposed MPA would stand for 70 years, with a review every decade so zones can be adjusted to preserve ecosystems.
No more disastrous delays
The commission is made up of 25 countries and the European Union. In its upcoming meeting, the proposed MPA will once again be considered. Two other important MPA proposals are also on the table in the East Antarctic and Weddell Sea.
In fact, for eight consecutive years, the proposal for a marine park in Eastern Antarctica has failed. Delays like this are potentially disastrous for the fragile ecosystem.
Protecting the peninsula is the most pressing priority due to rising threats, but the commission should adopt all three to fulfil their 2002 commitment to establishing an MPA network in Antarctica.
If all three were established, then more than 3.2 million square kilometres of the Southern Ocean would be protected, giving biodiversity a fighting chance against the compounding threats of human activity in the region.
While greenhouse gases are warming Earth’s surface, they’re also causing rapid cooling far above us, at the edge of space. In fact, the upper atmosphere about 90km above Antarctica is cooling at a rate ten times faster than the average warming at the planet’s surface.
Our new research has precisely measured this cooling rate, and revealed an important discovery: a new four-year temperature cycle in the polar atmosphere. The results, based on 24 years of continuous measurements by Australian scientists in Antarctica, were published in twopapers this month.
The findings show Earth’s upper atmosphere, in a region called the “mesosphere”, is extremely sensitive to rising greenhouse gas concentrations. This provides a new opportunity to monitor how well government interventions to reduce emissions are working.
Our project also monitors the spectacular natural phenomenon known as “noctilucent” or “night shining” clouds. While beautiful, the more frequent occurrence of these clouds is considered a bad sign for climate change.
Studying the ‘airglow’
Since the 1990s, scientists at Australia’s Davis research station have taken more than 600,000 measurements of the temperatures in the upper atmosphere above Antarctica. We’ve done this using sensitive optical instruments called spectrometers.
These instruments analyse the infrared glow radiating from so-called hydroxyl molecules, which exist in a thin layer about 87km above Earth’s surface. This “airglow” allows us to measure the temperature in this part of the atmosphere.
Our results show that in the high atmosphere above Antarctica, carbon dioxide and other greenhouse gases do not have the warming effect they do in the lower atmosphere (by colliding with other molecules). Instead the excess energy is radiated to space, causing a cooling effect.
Our new research more accurately determines this cooling rate. Over 24 years, the upper atmosphere temperature has cooled by about 3℃, or 1.2℃ per decade. That is about ten times greater than the average warming in the lower atmosphere – about 1.3℃ over the past century.
Untangling natural signals
Rising greenhouse gas emissions are contributing to the temperature changes we recorded, but a number of other influences are also at play. These include the seasonal cycle (warmer in winter, colder in summer) and the Sun’s 11-year activity cycle (which involves quieter and more intense solar periods) in the mesosphere.
One challenge of the research was untangling all these merged “signals” to work out the extent to which each was driving the changes we observed.
Surprisingly in this process, we discovered a new natural cycle not previously identified in the polar upper atmosphere. This four-year cycle which we called the Quasi-Quadrennial Oscillation (QQO), saw temperatures vary by 3-4℃ in the upper atmosphere.
Discovering this cycle was like stumbling across a gold nugget in a well-worked claim. More work is needed to determine its origin and full importance.
But the finding has big implications for climate modelling. The physics that drive this cycle are unlikely to be included in global models currently used to predict climate change. But a variation of 3-4℃ every four years is a large signal to ignore.
We don’t yet know what’s driving the oscillation. But whatever the answer, it also seems to affect the winds, sea surface temperatures, atmospheric pressure and sea ice concentrations around Antarctica.
‘Night shining’ clouds
Our research also monitors how cooling temperatures are affecting the occurrence of noctilucent or “night shining” clouds.
Noctilucent clouds are very rare – from Australian Antarctic stations we’ve recorded about ten observations since 1998. They occur at an altitude of about 80km in the polar regions during summer. You can only see them from the ground when the sun is below the horizon during twilight, but still shining on the high atmosphere.
The clouds appear as thin, pale blue, wavy filaments. They are comprised of ice crystals and require temperatures around minus 130℃ to form. While impressive, noctilucent clouds are considered a “canary in the coalmine” of climate change. Further cooling of the upper atmosphere as a result of greenhouse gas emissions will likely lead to more frequent noctilucent clouds.
There is already some evidence the clouds are becoming brighter and more widespread in the Northern Hemisphere.
Human-induced climate change threatens to alter radically the conditions for life on our planet. Over the next several decades – less than one lifetime – the average global air temperature is expected to increase, bringing with it sea level rise, weather extremes and changes to ecosystems across the world.
Long term monitoring is important to measure change and test and calibrate ever more complex climate models. Our results contribute to a global network of observations coordinated by the Network for Detection of Mesospheric Change for this purpose.
The accuracy of these models is critical to determining whether government and other interventions to curb climate change are indeed effective.
Australia wants to build a 2.7-kilometre concrete runway in Antarctica, the world’s biggest natural reserve. The plan, if approved, would have the largest footprint of any project in the continent’s history.
The runway is part of an aerodrome to be constructed near Davis Station, one of Australia’s three permanent bases in Antarctica. It would be the first concrete runway on the continent.
The plan is subject to federal environmental approval. It coincides with new research published this week showing Antarctica’s wild places need better protection. Human activity across Antarctica has been extensive in the past 200 years – particularly in the coastal, ice-free areas where most biodiversity is found.
Australia has successfully operated Davis Station since 1957 with existing transport arrangements. While the development may win Australia some strategic influence in Antarctica, it’s at odds with our strong history of environmental leadership in the region.
The Australian Antarctic Division (AAD), a federal government agency, argues the runway would allow year-round aviation access between Hobart and Antarctica.
Presently, the only Australian flights to Antarctica take place at the beginning and end of summer. Aircraft land at an aerodrome near the Casey research station, with interconnecting flights to other stations and sites on the continent. The stations are inaccessible by both air and ship in winter.
The AAD says year-round access to Antarctica would provide significant science benefits, including:
better understanding sea level rise and other climate change impacts
opportunities to study wildlife across the annual lifecycle of key species including krill, penguins, seals and seabirds
allowing scientists to research through winter.
Leading international scientists had called for improved, environmentally responsible access to Antarctica to support 21st-century science. However, the aerodrome project is likely to reduce access for scientists to Antarctica for years, due to the need to house construction workers.
Australia: an environmental leader?
Australia has traditionally been considered an environmental leader in Antarctica. For example, in 1989 under the Hawke government, it urged the world to abandon a mining convention in favour of a new deal to ban mining on the continent.
Australia’s 20 Year Action Plan promotes “leadership in environmental stewardship in Antarctica”, pledging to “minimise the environmental impact of Australia’s activities”.
But the aerodrome proposal appears at odds with that goal. It would cover 2.2 square kilometres, increasing the total “disturbance footprint” of all nations on the continent by 40%. It would also mean Australia has the biggest footprint of any nation, overtaking the United States.
Within this footprint, environmental effects will also be intense. Construction will require more than three million cubic metres of earthworks – levelling 60 vertical metres of hills and valleys along the length of the runway. This will inevitably cause dust emissions – on the windiest continent on Earth – and the effect of this on plants and animals in Antarctica is poorly understood.
Wilson’s storm petrels that nest at the site will be displaced. Native lichens, fungi and algae will be destroyed, and irreparable damage is expected at adjacent lakes.
Weddell seals breed within 500 metres of the proposed runway site. Federal environment officials recognise the dust from construction and subsequent noise from low flying aircraft have the potential to disturb these breeding colonies.
The proposed area is also important breeding habitat for Adélie penguins. Eight breeding sites in the region are listed as “important bird areas”. Federal environment officials state the penguins are likely to be impacted by human disturbance, dust, and noise from construction of the runway, with particular concern for oil spills and aircraft operations.
The summer population at Davis Station will need to almost double from 120 to 250 during construction. This will require new, permanent infrastructure and increase the station’s fuel and water consumption, and sewage discharged into the environment.
The AAD has proposed measures to limit environmental damage. These include gathering baseline data (against which to measure the project’s impact), analysing potential effects on birds and marine mammals and limiting disturbance where practicable.
But full details won’t be provided until later in the assessment process. We expect Australia will implement these measures to a high standard, but they will not offset the project’s environmental damage.
So given the environmental concern, why is Australia so determined to build the aerodrome? We believe the answer largely lies in Antarctic politics.
Australian officials have said the project would “contribute to both our presence and influence” on the continent. Influence in Antarctica has traditionally corresponded to the strength of a nation’s scientific program, its infrastructure presence and engagement in international decision-making.
Australia is a well-regarded member of the Antarctic Treaty. It was an original signatory and claims sovereignty over 42% of the continent. It also has a solid physical and scientific presence, maintaining three large year-round research stations.
But other nations are also vying for influence. China is constructing its fifth research station. New Zealand is planning a NZ$250 million upgrade to Scott Base. And on King George Island, six stations have been built within a 5km radius, each run by different nations. This presence is hard to justify on the basis of scientific interest alone.
Getting our priorities straight
We believe there are greater and more urgent opportunities for Australia to assert its leadership in Antarctica.
For example both Casey and Mawson stations – Australia’s two other permanent bases – discharge sewage into the pristine marine environment with little treatment. And outdated fuel technology at Australia’s three stations regularly causes diesel spills.
At Wilkes station, which Australia abandoned in the 1960s, thousands of tonnes of contaminants have been left behind.
Australia should fix such problems before adding more potentially damaging infrastructure. This would meet our environmental treaty obligations and show genuine Antarctic leadership.
Since Western explorers discovered Antarctica 200 years ago, human activity has been increasing. Now, more than 30 countries operate scientific stations in Antarctica, more than 50,000 tourists visit each year, and new infrastructure continues to be developed to meet this rising demand.
Determining if our activities have compromised Antarctica’s wilderness has, however, remained difficult.
Our study, published today in Nature, seeks to change that. Using a new “ecological informatics” approach, we’ve drawn together every available recorded visit by humans to the continent, over its 200 year history.
We found human activity across Antarctica has been extensive, especially in the ice-free and coastal areas, but that’s where most biodiversity is found. This means wilderness areas – parts of the continent largely untouched by human activity – do not capture many of the continent’s important biodiversity sites.
One of the world’s largest intact wildernesses
So just how large is the Antarctic wilderness? For the first time, our study calculated this area and how much biodiversity it captures. And, like all good questions, the answer is “that depends”.
If we think of Antarctica in the same way as every other continent, then the whole of Antarctica is a wilderness. It has no farms, no cities, no suburbs, no malls, no factories. And for a continent so large, it has very few people.
But Antarctica is too different to compare to other continents – it should be held to a higher standard. And so we define “wilderness” as the areas that aren’t highly impacted by people. This would exclude, for example, tourist areas and scientific stations. And under this definition, the wilderness area is still large.
It’s about 13,598,148 square kilometres, or more than 99% of the continent. Only the wilderness in the vast forested areas of the far Northern Hemisphere is larger. Roughly, this area is nearly twice the size of Australia.
On the other hand, the inviolate areas (places free from human interference) that the Antarctic Treaty Parties are obliged to identify and protect are dwindling rapidly.
Our analyses suggest less than 32% of the continent includes large, unvisited areas. And even that’s an overestimate. Not all visits have been recorded, and several new traverses – crossing large tracts of unvisited areas – are being planned.
Wilderness areas have poor biodiversity value
If so much of the continent remains “wild”, how much of Antarctica’s biodiversity lives within these areas?
Surprisingly few sites considered really important for Antarctic biodiversity are represented in the “un-impacted” wilderness area.
For example, only 16% of the continent’s Important Bird Areas (areas identified internationally as critical for bird conservation) are located in wilderness areas. And only 25% of protected areas established for their species or ecosystem value, and less than 7% of sites with recorded species, are in wilderness areas.
This outcome is surprising because wilderness areas elsewhere, like the Amazon rainforest, are typically valued as crucial habitat for biodiversity.
Inviolate areas have seemingly even less biodiversity value. This is because people have mostly had to visit Antarctic sites to collect species data.
In the future, remote sensing technologies might allow us to investigate and monitor pristine areas without setting foot in them. But for now, most of our knowledge of Antarctic species comes from places that have been impacted to some extent by people.
How does human activity threaten Antarctic biodiversity?
Antarctica’s remaining wilderness areas need urgent protection from increasing human activity.
Even passing human disturbance can impact the biodiversity and wilderness value of sites. For example, sensitive vegetation and soil communities can take years to recover from trampling.
Increasing movement around the continent also increases the risk people will transfer species between isolated regions, or introduce new alien species to Antarctica.
So how can we protect it?
Protecting the Antarctic wilderness could be achieved by expanding the existing Antarctic Specially Protected Areas network to include more wilderness and inviolate areas where policymakers would limit human activity.
When planning how we’ll use Antarctica in the future, we could also consider the trade off between the benefits of science and tourism activities, and the value of retaining pristine wilderness and inviolate areas.