Written in the ice: trends and predictions on climate change from the coldest regions of the planet

Sea ice dynamics profoundly influence the polar environment, with far-reaching impacts on global climate regulation and ocean circulation. The current trends in sea ice loss also significantly affect local ecosystems and livelihoods. A comprehensive understanding of sea ice dynamics is essential to accurately assess climate change scenarios. In a collection of the most recent CMCC research and papers on sea-ice, what we know and future challenges for science. (Spoiler: computational resources and the complexity of small-scale physical processes are among the keys.)

Arctic sea ice changes due to increased ocean heat content?

Arctic sea ice is a key component of the Earth’s climate system, and the extent of its seasonal variation reflects the impacts of climate change. The Arctic is experiencing changes in ocean circulation and an increasing heat flux exchange with the atmosphere in regions that are periodically ice-free. This increase calls for further research to fully understand the role of ocean heat content in driving sea ice changes on shorter timescales. A CMCC study found that since the mid-2000s, the Arctic has shifted toward a regime with higher ocean heat content in surface layers and accelerated rate of sea ice loss. These changes impact the dynamics of energy exchange between ice and the ocean and can be monitored through data assimilation techniques. The research suggests that monitoring variations in ocean heat content is essential to improve predictability of sea ice from three months to one month in advance, which is useful to implement effective local adaptation measures.?

The Arctic might lose its sea ice-cover by 2047

Quantifying the extent of sea ice loss in the Arctic is important to understand its impacts on the climate and ocean systems. A CMCC study examined the changes in Arctic sea ice evaluating the past and future variations through six different climate models, part of the High-Resolution Model Intercomparison Project (HighResMIP - CMIP6). All models found a significant reduction in sea ice volume up to 95% for the period 1950 to 2050. The research results reveal that the Arctic might be ice-free as soon as 2047. Furthermore, the sea ice cover characteristics are expected to change, with the marginal ice zone—the transitional zone between solid ice and the ocean—becoming predominant by 2050, a condition similar to that observed in the Antarctic.

Modeling sea ice winter heat conduction?

To improve predictions of sea ice cover, it is important to address model shortcomings in depicting the complexity of heat conduction within the sea ice system. The winter heat exchange between the ocean, sea ice, and the atmosphere is a key factor in the formation of new sea ice each in winter. Models can fail to capture the complexity of heat conduction through the ice system. In fact, generally they only consider vertical heat flows through the ice, however heat also transfers horizontally. This assumption may lead to an underestimation of around 10% of the total conductive heat flux. Improving model parametrization is crucial for accurately predicting climate feedbacks and informing policymakers on the impacts sea-ice loss on ecosystems and local communities.?

Predictive insights into Antarctic sea ice variability

Similarly to Arctic sea-ice cover, Antarctic sea ice has a critical role in the climate system, regulating the exchange of heat between the ocean and the atmosphere. Since the 1980s, Antarctic sea ice has shown strong variability, with overall trends indicating an increase due to interannual fluctuations, though specific regions like the Ross Sea and Antarctic Peninsula have experienced declines. Despite these observations, predicting decadal sea ice variability in the Antarctic remains challenging due to substantial uncertainty in the models. Research by CMCC and JAMSTEC highlights how decadal sea ice variability in the west Antarctic can be predicted using a coupled atmosphere-ocean-sea ice circulation model initialized with observation-based datasets..The study suggests that incorporating sea ice thickness estimates could further enhance predictions.

More info:?

• How predictable is Arctic sea ice variability?
• Past and future of the Arctic sea ice in High-Resolution Model Intercomparison Project (HighResMIP) climate models
• Sea ice: new understanding on the winter heat conduction problem
• Antarctic ice: a better knowledge of the ocean improves the predictability of sea ice variability