During wintertime, sea ice forms periodically in Norwegian fjords and coastal areas. Further north, sea ice covers large parts of the Arctic Ocean, and the same happens in the coastal areas around Antarctica. The sea ice in these areas has declined drastically in recent times and it is crucial to calculate the coming changes. The sea-ice model we use for the Arctic has now been modified to be able to provide insight into sea-ice dynamics in Antarctica.
The sea ice in the northern and southern polar regions behaves very differently. At the North Pole, the Arctic Ocean is surrounded by land. This provides calm weather conditions, so that the sea ice grows into large, thick floes that drift slowly over the ocean. In contrast, Antarctic sea ice is surrounded by the stormiest ocean on the planet, the Southern Ocean. Frequent storms and high waves cause the sea ice to break up repeatedly. This results in in small floes that strong winds and currents can quickly move around. Therefore, Antarctic sea ice is much more dynamic than its counterpart in the Arctic!
The Nansen Center’s sea-ice model neXtSIM, simulates very precisely how sea ice forms, moves and cracks. The model has been originally designed for sea ice in the Arctic. In collaboration with researchers from New Zealand, a new configuration dedicated to the southern hemisphere was recently created. Together, we investigated whether neXtSIM could be a useful tool to develop a better understanding of how Antarctic sea ice reacts to changes in winds and ocean currents.
Their recently published study shows that neXtSIM performs very well when it comes to simulating Antarctic sea ice. More than that, it showed unique capabilities at reproducing the fast motion of sea ice during the storms that frequently break the sea ice cover. neXtSIM for Antarctica has shown to function better than most sea-ice models, making it an invaluable asset to understand the evolution of Antarctic sea ice.
Antarctica has recently experienced dramatic sea ice losses, especially in 2023. This drastic decline remains difficult to explain, but researchers suspect storms may have played a large role in this recent development. Therefore, to understand the changes going on in that region, it is crucial that models simulate the interactions between sea ice and storms properly, and this is exactly what neXtSIM does well.
Changes in Antarctica have impacts far beyond the southern hemisphere. The Southern Ocean absorbs around 40% of anthropogenic CO₂ – more than twice as much as the world’s rainforests absorb, and sea ice plays a significant role in this cycle. It also shelters the ice sheets from the strong waves of the Southern Ocean. The loss of sea ice could therefore accelerate the demise of the big Antarctic ice sheets, leading to significant consequences, both locally for the Antarctic penguin population, and globally for the sea level. The next goal is now to use neXtSIM to improve the understanding how sea ice will evolve in Antarctica as climate warms. This will help the scientific community to better predict the changes that will occur in that region and their global impact.
Key researchers: Guillaume Boutin, Einar Ólason, Timothy Williams, Pierre Rampal
