© Prof Anna E. Hogg, University of Leeds

Climate change is taking a toll on every aspect of Antarctica – Expert Reaction

Extreme events from climate change have influenced every realm in Antarctica, including breeding failures of entire penguin colonies, ice shelf collapse, invasion of non-native plants, and the recent lack of winter sea ice, according to a review by UK scientists.

The UK authors conclude that fossil fuel burning will continue to affect the Antarctic environment, and countries which have adopted the Environmental Protocol of the Antarctic Treaty (including New Zealand) must ask themselves whether their greenhouse gas reduction targets will truly protect the icy continent.

Meanwhile, scientists at an Antarctic biology conference in Christchurch have published an open letter, calling attention to “dramatic changes at unprecedented rates” in the Antarctic, and for an “immediate increase in ambition” on reducing greenhouse gas emissions.

The SMC asked local experts to comment on the research.

Professor Nancy Bertler, Director, Antarctic Science Platform, comments:

“New Zealanders, as with other countries and communities around the world, have come to experience extreme climate change events with devastating consequences at a faster and faster rate. The paper by Siegert et al. is an impressive synthesis of extreme climate change events now observed in Antarctica, their impact on the continent and surrounding oceans, and the ecosystems it holds.

“Critically, the publication also highlights how these impacts have far reaching, global consequences – some understood, some yet to be identified – because what happens in Antarctica – never stays in Antarctica.

“From unprecedented heatwaves that led to warming of 40°C over the East Antarctic Plateau, to waterfalls gushing off ice shelves, to the unexpected and rapid disappearance of sea ice – Antarctica is changing at a pace that none of us anticipated.

“The drastic decrease in Antarctic sea ice since 2016 is equivalent to the total loss in Arctic sea ice over the past 30 years with 2023 to exceed previous record lows. While changes in Antarctic sea ice is perhaps not something many ponder on the daily basis, it is likely to impact every person on the planet. The annual growth of sea ice in the Antarctic and Arctic is a key driver of the global ocean circulation and with that the transport of vast amount of heat around the Earth and the uptake of atmospheric CO2 into the deep ocean. Changes to this circulation changes where we anticipate heatwaves, droughts, floods, and fires. It also has the potential to accelerate atmospheric CO2 concentrations and with that the global warming trend.

“Siegert et al. add to the urgency noted by the United Nations, IPCC, the SCAR Decadal Report, the SCAR Biology Symposium Christchurch Communique, that humanity has to act now, that we have to reduce our emissions by 50% by 2030 to have any chance to achieve the Paris Agreement. We all depend on it.”

No conflict of interest declared.

Dr Mario Krapp, Data Scientist (Climate & Environment), GNS Science | Te Pū Ao, comments:

“This review from Siegert and his team underscores the context of Antarctic extreme events. 2023 is (again) a year of extremes. Whereas in normal years, the Southern Ocean around Antarctica this time of the year is covered by approximately 17 million square kilometres of sea ice, equivalent to an area roughly the size of 63 New Zealands, this year, we are witnessing a staggering loss of an area of about nine New Zealands. 2023 is off the charts, literally.

“Described as a “1 in a 7.5 million year event”, this extreme sea-ice minimum cannot be solely attributed to natural climate variability; rather, it is driven by excess energy in the climate system, stemming from human-induced greenhouse gas emissions. The consequences are evident through the surge in extreme events globally, from heatwaves and floods to storms, wildfires, and tornadoes – all manifestations of the climate system’s attempt to dissipate the surplus energy.

“Climate inaction has already set in motion irreversible changes. And while the oceans have been absorbing 90% of the excess energy, they cannot keep up for much longer. Warmer oceans are the likely culprit preventing sea-ice formation around Antarctica, mirroring the gradual decline observed in the Arctic. Understanding these extreme events is vital, as Siegert and his team remind us of the consequences of neglecting climate change.

“15 years ago, James Lovelock, co-author of the Gaia Hypothesis, said, “enjoy life while you can: in 20 years global warming will hit the fan”. He may have been off by five years.

“Coping with a single extreme event is challenging enough; the prospect of dealing with compounded effects of multiple extreme events coming together year after year is worrying and demands immediate attention and action from individuals and policymakers alike.”

No conflict of interest declared.

Professor Craig Stevens, Principal Scientist – Marine Physics, NIWA; and Professor of Physics, University of Auckland, comments:

“The environmental changes around Antarctica are coming so fast it is difficult for researchers, let alone everyone else, to keep up with the studies that are documenting the impacts. It makes reviews like this a valuable synthesis of the types of extrema happening to the region.

“I like how the paper looks at the problem from a couple of dimensions. They look at all the themes that are being affected by the changing climate now. This runs from the shrinking ice of all kinds through to oceans, biodiversity as well as atmospheric changes.

“Then this is contextualized by climate-induced past changes. Several key knowledge gaps are highlighted, such as sea ice thickness, usefully reminding us that not everything is known about the system.

“Because change in Antarctica is not masked by the activities of large local human populations, the impacts are very stark.

“The evidence for a cascade of extreme events is exactly the concern identified by the research community for decades. Because of this, the study will need constant updating as the scale of change evolves – there are new studies that have come out even in the short time between when the paper was written and published.

“The work is another clear signal from the research community that in order to maintain present levels of quality of life, the majority of our societies need to rapidly and comprehensively shift away from greenhouse gas emitting activity.”

No conflict of interest.

Alexandra Gossart, Research Fellow in Climate Modelling, Antarctic Research Centre, Victoria University of Wellington, comments:

“Even though my daily work includes words such as ‘extreme’, ‘intense’, ‘catastrophic’ and ‘global impacts’, having all of these linked to various aspects of the icy continent is eye-opening. Listing the changes happening and likely to become more present in the future is extremely powerful, especially because the authors touch upon various realms (atmosphere – ocean – land ice and sea ice – biology and ecology) and their interactions.

“I cannot help but think of the recent discussions about this year’s very low sea ice extent, a scary memory of similar conversations already had last year. And to link it to extreme events we experienced here in Aotearoa over the past few months, as well as the current heat waves affecting Europe, and even South America. The shift of what we referred to as high magnitude, low frequency events to regular or even yearly events, is real. While this concern is not new and has been expressed over and over again by scientists, it is now apparent and for all to see.

“It is clear to me (probably because as a climate modeller – I am biased) that the paper is calling for improving research, in order to constrain uncertainties of both timing and magnitude of the occurrence of extreme events. It is striking that the last column of “Table 1″ contains a lot of uncertainty due to model deficiencies, and complex, poorly understood processes. The international community is striving to provide better understanding and reduce uncertainties of these processes. But I cannot resist wondering – how do we carry this out with chronically underfunded universities, systemic issues in the research funding schemes, and the government’s disinvestment in Strategic Science Investment Fund? Even though our coasts are directly threatened by sea level rise and evidence of intensification of extreme events is obvious?”

No conflict of interest.

Associate Professor Jonathan Tonkin, Community Ecology, University of Canterbury, comments:

“Climate change has led to increased frequencies and magnitudes of extreme environmental events globally. These are increasingly in the public eye due to their direct impact on society, such as via floods, wildfires, hurricanes and drought. Less obvious, though, is their impact on remote places like Antarctica. The authors of this paper summarise extreme events in Antarctica and demonstrate their multi-pronged consequences. Particularly telling is how vulnerable Antarctic ecosystems are, but also how consequential these events can be for the rest of the world.

“It is clear that we must act immediately to stem the runaway nature of the current situation. Of clear concern is the threat of cascading extreme events that can build on each other to amplify their individual impacts. Antarctica must be protected, but much of this protection comes from controlling harmful greenhouse gas emissions, something we already know must be done to control climate change.

“From an ecological perspective, the threats are widespread, including increased impacts from alien species, altered freeze-thaw cycles, changing snowfall and snowpack conditions for land species, altered distribution of freshwater resources, redistribution or loss of sea ice, and complete reorganisation of the marine food-web. While Antarctic species have evolved to cope with extreme environments, their tolerance has limits.

“One thing we must do is continue our focus on understanding the mechanistic ways in which biodiversity responds to extreme events and environmental change more generally. By doing so, we will be much better placed to forecast how biodiversity might respond to future events, and this will help direct action. We recently published a paper focusing on this question, outlining a roadmap for forecasting the future of life in Antarctica.”

No conflict of interest.

Dr Lauren Vargo, Research Fellow, Antarctic Research Centre, Victoria University of Wellington, comments:

“I appreciate the overview of the different components of Antarctica and changes that we are seeing. Additionally, I hope this work continues to generate awareness and inform people on the impacts of climate change (e.g. Antarctica’s contributions to sea level rise have been increasing and will likely continue to do so).

“Hopefully this paper generates more science! The authors repeatedly note that an extreme event occurred (e.g. heatwave of 38.5°C higher than average temperatures over East Antarctica in March 2022) but go on to note that no formal attribution of the event has been done.

“Scientists can and do calculate the increases in severity and likelihood of extreme events happening due to climate change. For example, New Zealand researchers found that the May 2021 Canterbury floods were 10 – 15% more intense due to human influence. So, I was disappointed to not see any attribution of the extreme events in this work, but hopefully that will come!

“I found the author’s definition of ‘extreme events’ confusing. Researchers who work in studying extreme events usually define them as the 5th percentile of events (e.g. a period of rainfall that is heavier than 95% of all rainfall events). This paper seems to imply that processes like 1) meltwater on ice, 2) ice streams (parts of the ice sheet where ice flows more quickly), and 3) winds blowing dust onto ice are all extreme and could be due to climate change. This isn’t quite true, all could and would have occurred without human-driven climate change.

“The paper does bring up some key points that are likely impacts of warming temperatures (due to burning fossil fuels). Particularly concerning of which are rising sea levels as ice melt quickens and record low sea ice extent, which is at its lowest extent since records became available in 1978.”

No conflict of interest.

Professor Tim Naish, Director, Antarctic Research Centre, Victoria University of Wellington, comments:

“The paper by Siegert et al is a timely call to us that, as global heating approaches the Paris climate limit of 1.5°C above the pre-industrial global average, Antarctica is experiencing more and more extreme events. In some cases we are getting dangerously close to tipping points, which once crossed will lead to irreversible change with unstoppbale consequences for future generations.

“Some of the warning signs include the unprecedented heatwave of March 2022 which saw temperatures increase by nearly 40°C over Concordia Station in East Antarctica, and the dramatic decline in winter sea-ice extent since 2016.

“This years sea-ice minimum is 20% lower than the average of the last 40 years and is equivalent to sea ice loss of an area nearly 10 times New Zealand. This causes an amplified warming feedback, whereby white sea-ice which reflects 90% of the incoming solar radition is replaced by dark ocean which absorbs 90% of the radiation. Many researchers are asking if it is now not possible to reverse this trend. Time well tell, but as the southern ocean continues to warm (it has taken up 70% of the heat from human warming so far) the margins of Antarctica’s ice sheets are melting at an accelerating rate. Numerical climate and ice sheet models and evidence from past climate records shows that the West Antarctic Ice Sheet may irrevesibly melt if warming is sutained above 1.5°C. Above 2°C of warming, parts of the East Antarctic Ice Sheet will also melt, committing the planet to as much as 20m of global sea-level rise over coming centuries.

“The rececent report from the WMO predicts that we will be at 1.5°C in the next 5 years. This together with the increased occurrence of extreme weather events in Antarctica and elsewhere, has heightened global concern, and has shown that the policy repsonse so far has been inadequate to address the climate crisis. The IPCC in their latest synthesis report reminds us that there are still multiple feasible pathways to avoid 2°C of global warming, but we must all act now at pace and scale.”

Conflict of interest statement: “I am funded by the MBIE Antarctic Science Platform and the MBIE Our Changing Coast programme. I was a Lead Author on IPCC AR5 Report and I am on the Joint Scientific committee of the World Climate Research Programme.”

Dr Natalie Robinson, Antarctic Oceanographer, NIWA, comments:

“This is an effective and very useful high-level summary of Antarctica’s vulnerability to the current climate shifts. All of the statements are in line with the current scientific consensus, with no unsubstantiated statements as far as I’m aware. In describing both the size and potential impact of Antarctica’s climate vulnerabilities, the paper presents a measured and balanced assessment which, while sobering, in no way overstates the situation.

“Antarctica is a delicately-balanced system, highly sensitive to changes that elsewhere would be considered small or even insignificant. That’s because even small shifts are enough to cross the freezing point, and therefore change the physical state of the environment. The heatwave of 2022 saw temperatures nearly 40˚C higher than normal in parts of East Antarctica, delivering +7˚C and liquid rain to the Australian Casey station.

“Antarctic sea ice – the apron of frozen ocean around Antarctica that forms each winter and breaks up again each summer – has been highly dynamic over the entire satellite record (i.e. since 1979). But that variability has really ramped up in the past decade. In that time, we have seen both record highs and lows of total sea ice extent, with many months falling outside of the range of variability that had been seen prior to 2010. This makes is very difficult to predict what will happen next, but the fact that a record low of 2022 was followed by an even more significant drop in 2023 is very real cause for concern. This is because sea ice performs a whole host of functions that moderate our climate (listed below). For context, the present area of ‘missing’ sea ice is around 20% of the total sea ice extent, roughly equal to 10x the area of New Zealand.

“The Southern Ocean is a complex system with a changes cascading through multiple parts of the system and potentially feeding back on itself through multiple mechanisms. This makes it very difficult to predict exactly how things will play out.

“Christchurch is presently hosting a meeting of the world’s top Antarctic biologists. The recent extreme events and the rapid rate of change in Antarctica have alarmed the international scientific community. The result will be a statement, ‘The Christchurch Communique’, signed by hundreds of Antarctic scientists, calling on all nations to “intensify and exceed their current commitments to greenhouse gas emissions reductions.” because “an immediate increase in ambition is required to reach net zero…””

Why should New Zealanders care?

“New Zealand’s climate is strongly influenced by heat and moisture carried by the ocean. The Southern Ocean has taken up most of the extra heat from human activities and the tropics are pushing southward. This means that, across the latitudes that NZ occupies, there are stronger gradients, more energy, and more propensity for the atmosphere to take up moisture from the ocean. NZ is therefore in the firing line of a more energetic ocean/atmosphere system, capable of delivering more intense storm and rain events, with increasing frequency.”

The five most important effects that sea ice has on the global climate system:

  1. “Albedo Effect: The vast sheet of white reflects ~90% of incoming solar radiation back out to space (even more if it has snow on top), preventing it from being absorbed to heat up our system. In contrast, the dark ocean waters that it forms from absorb ~90% of that heat. As more heat is absorbed, it makes it less likely for ice to form so more heat is absorbed rather than reflected. This is a ‘self-reinforcing’ process.
  2. Ocean Overturning: The huge volumes of cold salty that are produced as a by-product of sea ice formation drive global ocean overturning, controlling how heat and nutrients are distributed throughout the global ocean. ~40% of all ocean waters can be traced back to Antarctic sea ice formation
  3. Drawdown of heat: This process of deep sinking also draws heat out of the atmosphere to deliver it to the deep ocean. To date, the global oceans have taken up 93% of the extra heat in the climate system from human activities (compared with ~1% taken up by the atmosphere). And the Southern Ocean has taken up ~2/3 of that.
  4. Drawdown of CO2: In a similar way, CO2 is drawn down out of the atmosphere and delivered to the deepest ocean basins. However, the return flow also brings CO2 that has been stored down deep back up to the surface. So the net effect is a small number which is the balance between two very large numbers. At present the net effect is drawdown of CO2 by the Southern Ocean, but this could change as things get stormier.
  5. Ecosystem support: the vast surface of the sea ice provides a surface for algae to grow on – these perform a similar function to grass meadows in terrestrial ecosystems. So sea ice provides the foundational support for the entire marine food web. Also, Emperor Penguins need the sea ice to breed on, so as the sea ice declines, we expect to see them in similar decline. If we stay on track with current rates of emissions, Emperors are predicted to decline by >80% by 2100.”
No conflict of interest.

Associate Professor Inga Smith, Co-Director, He Kaupapa Hononga: Otago’s Climate Change Research Network, University of Otago, comments:

“This very readable paper should be on the must-read list for all policymakers and politicians globally. The paper is a useful and timely summary of current knowledge about Antarctica and the Southern Ocean’s vulnerability to climate change-related extreme events and other human-induced impacts. The paper will be useful for interested members of the public to get an overview of the complex and compounding issues with Antarctic extreme events.

“Perhaps the most important aspect of the paper is that it outlines what is unknown about Antarctic extreme events, such as how thick Antarctic sea ice currently is, how it will change in the future, and therefore how sea ice volume will change. The paper also points out the risk of cascading extreme events. The authors reiterate the need for international collaboration to understand and predict extreme events, and to assess their consequences.”

No conflict of interest declared.