Thinner Arctic sea ice may affect the AMOC
image:
Thinner sea ice in the Arctic could eventually have an impact on AMOC, more research is needed to better understand the link between less Arctic sea ice and the AMOC.
view moreCredit: Photo: Alfred Wegener Institute / Stefan Hendricks
One of the ocean currents in the Arctic Ocean is at risk of disappearing this century because of climate change, according to a new joint study from the University of Gothenburg and the German Alfred Wegener Institute. As a result, the North Atlantic could be flooded with freshwater which would weaken the global ocean circulation.
The weakening of the AMOC, Atlantic Meridional Overturning Circulation, is a hot topic among the world's climate scientists. However, it is unclear what the consequences will be when the ocean currents change and when a tipping point is reached. Researcher Céline Heuzé from the University of Gothenburg, together with colleagues Marylou Athanase and Raphael Köhler from Germany, has studied the future of one of the major ocean currents in the Beaufort Sea, located in the Arctic Ocean, north of the Alaskan and Canadian coasts.
This current is the Beaufort Gyre and it is an important feature of the Arctic Ocean. By storing or releasing freshwater, it influences the oceanic properties both within the Arctic and as far away as the North Atlantic.
Due to warmer temperatures in the Arctic, the Beaufort Gyre is currently losing large amounts of sea ice. The ice helps keeping the ocean cool, acting as a lid. Thinner sea ice allows more heat from the atmosphere to pass through, raising sea temperatures further and causing even more sea ice to disappear. Previous research shows that the freshwater content of the Beaufort Sea has increased by 40 percent over the last two decades.
Concerns about sea ice 'tipping point'
“The results of this study make us concerned that the reduction of sea ice in the area could lead to a tipping point where the AMOC collapses,” says Céline Heuzé, Senior Lecturer in Climatology at the University of Gothenburg and an expert on deep ocean and sea ice.
In the study, the researchers made projections using only the global climate models that can accurately represent the Beaufort Gyre. A climate model is a computer simulation of the Earth's climate system – atmosphere, ocean, land and ice. Climate models are used to reconstruct the past climate or predict the future climate.
“If greenhouse gas emissions are not reduced urgently, this projection suggests that the Beaufort Gyre will weaken and release the freshwater that it currently holds. This freshwater could then reach the North Atlantic and possibly negatively impact the AMOC,” says Marylou Athanase, researcher at Alfred Wegener Institute, Germany, and first author of the study.
The AMOC, of which the Gulf Stream is a part, is of great importance for the climate in Scandinavia as it transports warm water to high latitudes in the northern hemisphere. How the link between reduced Arctic sea ice and a weakening of the AMOC may develop in the future is something the researchers now want to study more closely.
Fact box: The Gulf Stream and the AMOC
The ocean circulation in the Atlantic that many climate scientists focus on is called the AMOC – Atlantic Meridional Overturning Circulation. It is a large system of ocean currents in the Atlantic, of which the Gulf Stream is a part. The AMOC system is driven by differences in density between different water masses so that warm water from more southerly latitudes moves north along the ocean surface where it cools, sinks and moves south again into the deep ocean. (Wikipedia)
Fact box: Tipping points
In climate science, a tipping point is a critical threshold that, when crossed, leads to large, accelerating and often irreversible changes in the climate system. (Wikipedia)
The Beaufort Gyre in the Arctic Ocean holds today large amounts of fresh water. If the gyre weakens due to climate change, it will release freshwater that could flood the North Atlantic and have an impact on the AMOC.
Credit
Illustration: Alfred Wegener Institute/Marylou Athanase
Journal
Journal of Geophysical Research Oceans
Method of Research
Computational simulation/modeling
Article Title
The Arctic Beaufort Gyre in CMIP6 Models: Present and Future
Article Publication Date
31-Mar-2025
PKU Scientists simulate the origin and evolution of the North Atlantic Oscillation
Peking University
Peking University, March 31, 2025: A simulation on the origin and evolution of North Atlantic Oscillation (NAO) has been conducted by a PKU research team led by Nie Ji, Associate Professor of School of Physics, and Hu Yongyun, Dean of Institute of Ocean Research, along with a research team from National Natural Science Foundation of China. Their study, recently published in Nature Communications, reveals the coherent relationship between NAO and the evolution of continents, mountains and oceans.
Why It Matters:
NAO plays a critical role in shaping climate patterns, affecting temperature, precipitation, and storms across regions like Europe, China, and North America. Understanding its geological origins provides insights into past climate variability and helps refine climate prediction models.
Methodology
·Time slice simuation t spans from 160 million years ago (Ma) to the present, analyzing how atmospheric pressure patterns evolved as the North Atlantic widened.
·Idealized experiments testing whether a minimum ocean basin width is necessary for NAO formation.
·Rocky Mountain uplift simulations to evaluate how topographic stationary waves influenced NAO internsity after 40 Ma.
Key Findings
·NAO emerged around 80–60 Ma when the North Atlantic expanded to ~40° longitude.
·Land-sea temperature contrast triggered NAO by shaping westerly jets and storm tracks.
·Rocky Mountain uplift (~40 Ma) further intensified NAO.
·Plate tectonics drive atmospheric circulation evolution over geological timescales.
Future Prospects
Results have some limitations that require further investigation. It’s still needed to explore the evolution of the leading EOF of extratropical geopotential variation across the entire Northern Hemisphere. Further investigations are needed to disentangle the roles of climate, the Tibetan Plateau, and the RM in shaping NH atmospheric circulation.
*This article is featured in PKU News' "Why It Matters" series. More from this series.
Click “here” to read the paper.
Written by: Akaash Babar
Edited by: Zhang Jiang
Source: Department of Atmospheric and Oceanic Sciences, School of Physics
Journal
Nature Communications
Article Title
Origin and evolution of the North Atlantic Oscillation
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