Study yields new insights into the link between global warming and rising sea levels
Understanding the relationship between the Antarctic Ice Sheet and the earth beneath is key to predicting future climate change impacts, finds McGill-led study
McGill University
image:
The ANET-POLENET team flew to remote field sites on Antarctica's Backer Islands to record bedrock uplift. Ohio State University co-author Terry Wilson is second from the left. (Credit: Nicolas Bayou)
view moreCredit: Nicolas Bayou
A McGill-led study suggests that Earth's natural forces could substantially reduce Antarctica’s impact on rising sea levels, but only if carbon emissions are swiftly reduced in the coming decades. By the same token, if emissions continue on the current trajectory, Antarctic ice loss could lead to more future sea level rise than previously thought.
The finding is significant because the Antarctic Ice Sheet is the largest ice mass on Earth, and the biggest uncertainty in predicting future sea levels is how this ice will respond to climate change.
“With nearly 700 million people living in coastal areas and the potential cost of sea-level rise reaching trillions of dollars by the end of the century, understanding the domino effect of Antarctic ice melt is crucial,” said lead author Natalya Gomez, an Associate Professor in McGill’s Department of Earth and Planetary Sciences and Canada Research Chair in Ice sheet - Sea level interactions.
The study focuses on how the ice sheet interacts with the earth beneath, and how that dynamic is influenced by carbon-emission levels. This relationship has not been thoroughly explored in previous studies, the researchers said.
“Our findings show that while some sea level rise is inevitable, swift and substantive action to lower emissions could prevent some of the most destructive impacts of climate change, particularly for coastal communities,” Gomez said.
Rising seas and nature’s double-edged sword
As ice melts, its weight decreases, causing the land beneath it to rise like an expanding sponge. The researchers say this process, called post-glacial uplift, can be a double-edged sword.
If emissions drop quickly, limiting global warming, post-glacial uplift can act as a natural brake on ice-mass loss. It lifts the ice up, slowing the flow of ice from land to ocean. The study found this dynamic can reduce Antarctica’s contribution to sea- level rise by up to 40 per cent.
However, if carbon outputs keep pace and the planet heats up quickly, the rebounding land will not be enough to slow the rapidly melting ice, and instead pushes more ocean water away from Antarctica, accelerating sea-level rise along populated coastlines.
To reach their findings, Gomez and collaborating scholars from Canada and the United States developed a 3-D model of Earth’s interior. Their model used geophysical field measurements from the U.S. ANET-POLENET project, which had pioneered large-scale deployments of sensitive instruments to record the bedrock uplift and seismic signals across large expanses of Antarctica. These extensive field measurements were essential for characterizing the three-dimensional variations of the Antarctic mantle incorporated in the study.
“Our 3-D model peels back Earth’s layers like an onion, revealing dramatic variations in thickness and consistency of the mantle below. This knowledge helps us better predict how different areas will respond to melting,” said co-author Maryam Yousefi, a geodesist at Natural Resources Canada and previously a Postdoctoral Fellow at McGill and Penn State universities.
It’s the first model to capture the relationship between Antarctica's ice and underlying earth in such detail, she added.
Notes Rob DeConto, a co-author and glaciologist at the University of Massachusetts, “This study marks a breakthrough in our ability to better predict the impacts of climate change on rising seas and to inform effective environmental policy.”
Global impacts
The findings, published in Science Advances, highlight the inequalities of climate change, the scholars noted. Island nations, which contribute the least to global emissions, are likely to bear the brunt of their consequences, they said.
The study is a collaboration between researchers at McGill, Pennsylvania State, Cambridge, Columbia, Colorado State, Ohio State, the University of Massachusetts Amherst, the University of Washington and the Union of Concerned Scientists. It was funded by the Canadian Natural Sciences and Engineering Research Council, the U.S. National Science Foundation and the Canada Research Chairs program.
About McGill University
Founded in 1821, McGill University is home to exceptional students, faculty, and staff from across Canada and around the world. It is consistently ranked as one of the top universities, both nationally and internationally. It is a world-renowned institution of higher learning with research activities spanning three campuses, 12 faculties, 14 professional schools, 300 programs of study and over 39,000 students, including more than 10,400 graduate students.
McGill’s commitment to sustainability reaches back several decades and spans scales from local to global. The sustainability declarations that we have signed affirm our role in helping to shape a future where people and the planet can flourish.
Backer Island GNSS system
The field team used specialized instruments from the ANET-POLENET project that measure Antarctica’s ground motion. This GNSS [GPS] station is located on an island of the Backer Islands chain in Pine Island Bay where the massive Pine Island Glacier enters the Amundsen Sea.
Credit
Terry Wilson
Journal
Science Advances
Method of Research
Computational simulation/modeling
Article Title
The influence of realistic 3-D mantle viscosity on Antarctica’s contribution to future 3 global sea levels
Article Publication Date
2-Aug-2024
Study shows link between asymmetric polar ice sheet evolution and global climate
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Icebergs collapsing from the Antarctic Ice Sheet
view moreCredit: Photo by LI Yuansheng
Recent joint research led by Professor AN Zhisheng from the Institute of Earth Environment of the Chinese Academy of Sciences has revealed the pivotal role of the growth of the Antarctic ice sheet and associated Southern Hemisphere sea ice expansion in triggering the mid-Pleistocene climate transition (MPT). It has also shown how asymmetric polar ice sheet evolution affects global climate.
The MPT refers to a shift in Earth’s climate system between about ~1.25–0.7 million years ago, marking a shift to more pronounced and regular glacial-interglacial cycles.
While providing insight into the rapid expansion of the Northern Hemisphere ice sheet since the mid-Pleistocene, this study also challenges numerous hypotheses regarding the origin and mechanisms behind the MPT.
Results of the research were published in the recent issue of Science, entitled “Mid-Pleistocene climate transition triggered by Antarctic ice sheet growth.”
Due to the importance of the MPT for the evolution of Earth’s ice sheet dynamics over the last ~1.25 million years, such hypotheses have been debated and discussed frequently in the journals Nature and Science over the last decades.
“This study contributes to our understanding of the question ‘What causes ice ages?’ —one of the 125 frontier scientific problems raised by Science/AAAS in 2021,” said Professor AN, also a member of Chinese Academy of Sciences (CAS) and Foreign Associate of the National Academy of Sciences, USA.
This work also illustrates how processes in the Earth system define and change characteristics of glacial-interglacial cycles, their dynamics, and their length.
Integrating geological records with numerical climate simulations, this study reveals the history of the asymmetric evolution of ice sheets in both hemispheres and the associated response of the Earth’s climate system.
The findings indicate that 2–1.25 million years ago, the ongoing growth of the Antarctic ice sheet and the associated expansion of sea ice in the Southern Hemisphere triggered a temperature drop and water vapor boost in the Northern Hemisphere through the modified cross-equatorial pressure gradient and meridional overturning circulation.
These changes thus fostered development of the Arctic ice sheet and ultimately caused a shift in Earth’s glacial cycles from ~40,000 years to ~100,000 years.
By examining the changes in ice volume across both hemispheres, this work highlights the profound impact of the asymmetric evolution of polar ice sheets upon global climate, particularly on the climate of the Northern Hemisphere.
“The finding of the study that this asymmetry could trigger powerful positive feedbacks that could induce a massive change to Earth’s climate, a point previously unappreciated until now, has important implications for understanding and projecting Earth’s climate under greenhouse warming,” said Dr. CAI Wenju, Fellow of the Australian Academy of Science, who noted that the study is an example of Chinese scientists taking the lead in solving global questions in frontier science.
Prof. AN indicated it was urgent to quantitatively assess links between asymmetric bi-hemispheric ice sheet melting and global climate change. He suggested doing so could advance our ability “to predict future climate change and response of the Earth System to the changes in polar ice sheets.”
This research was a collaboration with international teams including the CAS Institute of Tibetan Plateau Research, the University of Hong Kong, the British Antarctic Survey, Laoshan Laboratory, the Alfred Wegener Institute, Xi’an Jiaotong University, Nanjing University, Brown University, Beijing Normal University, Ocean University of China, and Australian National University.
Clouds typical of Antarctica, influenced by gravity waves, hover above a massive iceberg that has collapsed from an ice sheet.
Credit
Photo by BAN Chao
Journal
Science
Article Title
Mid-Pleistocene climate transition triggered by Antarctic ice sheet growth
Article Publication Date
1-Aug-2024
How the rising earth in Antarctica will impact future sea level rise
Effects will depend on how much global warming is controlled, study finds
Ohio State University
COLUMBUS, Ohio – The rising earth beneath the Antarctic Ice Sheet will likely become a major factor in future sea level rise, a new study suggests.
Despite feeling like a stationary mass, most solid ground is undergoing a process of deformation, sinking and rising in response to many environmental factors. In Antarctica, melting glacial ice means less weight on the bedrock below, allowing it to rise. How the rising earth interacts with the overlying ice sheet to affect sea level rise is not well-studied, said Terry Wilson, co-author of the study and a senior research scientist at the Byrd Polar and Climate Research Center at The Ohio State University.
In the new study, Wilson’s colleagues at McGill University developed a model to predict how these interactions could impact global sea level, finding that if humans can lower greenhouse gas emissions and global warming is slowed, upward shifts in the solid earth could reduce Antarctica’s contribution to sea level rise by about 40%, significantly bolstering the best case scenarios for global sea level rise. In this low-emissions scenario, land uplift slows the flow of ice from land to ocean, allowing for more of the ice sheet to be preserved.
Conversely, if humans are unable to lower carbon emissions in time, ice retreat will outpace uplift, pushing ocean water away from Antarctica and amplifying sea level rise. These events could significantly worsen the most dire models of projected sea level rise along populated coastlines, said Wilson.
“Our measurements show that the solid earth that forms the base of the Antarctic ice sheet is changing shape surprisingly quickly,“ said Wilson. “The land uplift from reduced ice on the surface is happening in decades, rather than over thousands of years.”
The study was published today in Science Advances.
To arrive at these conclusions, the team developed a 3D model of the Earth’s interior using geophysical field measurements from the Antarctic Network (ANET) of the Polar Earth Observing Network (POLENET) project. The mission is focused on studying the changing polar regions by collecting GPS and seismic data from an array of autonomous systems across Antarctica.
Researchers then performed a number of simulations to capture many possible evolutions of Antarctica’s ice sheet and the extent of global sea level rise Earth may experience until the year 2500, according to those parameters.
“We can project what difference it actually will make if we all contribute to a low-emission scenario now, versus what’s come to be called ‘business as usual’ emissions,” said Wilson, who is also the lead investigator of the ANET-POLENET project.
She attributes the model’s unprecedented level of detail to how deftly it incorporates data from Antarctica. GPS stations monitor how the land is moving and seismometers measure how fast seismic waves from earthquakes travel through the earth, yielding important insight into where the land uplift will be fast or slow.
Surprisingly, according to some of the team’s GPS observations processed by researchers at Ohio State, Wilson said, the Antarctic Ice Sheet is currently experiencing a solid earth uplift of about 5 centimeters per year, about 5 times the rate that North America experiences.
Another significant aspect of the study is how the changes in Antarctica under different carbon emissions scenarios will impact coastlines around the world. Because sea level change will not be uniform, the study notes that nearly 700 million people around the world living in coastal regions will be most impacted by rising seas due to Antarctic ice loss.
Since some regions, such as small island nations, will be more vulnerable than others, mitigating environmental conditions like atmospheric and ocean warming is a vital issue for society, said Wilson.
“Many people are now more aware they’re experiencing the effects of climate change,” she said. “This work reinforces that our actions as individuals, nations and globally can make a difference in what kind of Earth our offspring will experience in their lifetimes.”
The study results highlight how complex the relationship between the solid earth and the processes that happen atop it is, as well as the importance of continuing to gather enough data to make prompt and accurate predictions about what the next few centuries of our planet will look like.
“There’s a lot of uncertainty in every model and every prediction that you make,” said Wilson. “But to document how fast our world is changing, it’s very important to continue advancing our ability to make predictions that are more certain, which is the only path that will allow us to tend to our future in a meaningful way.”
Wilson completed the study with colleagues from McGill University, Pennsylvania State University, the University of Massachusetts Amherst, Columbia University, Washington University, Colorado State University and the Union of Concerned Scientists. This study was supported by the U.S National Science Foundation and the Natural Sciences and Engineering Research Council of Canada.
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Contact: Terry Wilson, Wilson.43@osu.edu
Written by: Tatyana Woodall, Woodall.52@osu.ed
Journal
Science Advances
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
The influence of realistic 3D mantle viscosity on Antarctica’s contribution to future global sea levels
Article Publication Date
2-Aug-2024
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