As the Arctic continues to experience rising sea temperatures is it possible to accurately predict the impact this will have on sea ice variability at sub-seasonal timescales? A new study conducted by CMCC researchers looks at ocean heat transports and surface heat fluxes between 1980–2021, revealing that heat stored in the ocean has important implications for the predictability of sea ice.

In recent decades, the Arctic Ocean has undergone changes associated with enhanced poleward inflow of Atlantic and Pacific waters and increased heat flux exchange with the atmosphere in seasonally ice-free regions.

The associated changes in upper-ocean heat content can alter the exchange of energy at the ocean–ice interface. However, the role of ocean heat content in modulating Arctic sea ice variability at sub-seasonal timescales is still poorly documented.

A new study, entirely coordinated by CMCC and relying on the CMCC C-GLORS ocean reanalysis dataset, addresses this issue by looking at how the energy budget of the Arctic Ocean and its regional seas changed over the past four decades in the context of the widespread Arctic warming.

“We found that around the mid-2000’s, most of the Arctic seas shifted towards a regime characterized by changes in the heat flux exchange between the ocean and atmosphere, increased heat absorption and storage by the ocean surface layers, and faster sea ice loss,” says CMCC researcher and lead author of the study, Elena Bianco. “Quantitatively this phenomenon can be described as an increase in ocean heat content, which can be measured using high-resolution data products that rely on data assimilation techniques.”

The study reveals that over the last couple of decades (2001-2021), ocean heat content and sea ice cover have become increasingly coupled, mainly due to the fact that sea ice is thinner and more vulnerable to bottom melting. This has important implications for the Arctic sea ice cover, as a surplus of ocean heat content in the summer can slow down sea ice formation in the autumn and winter.

A key implication of these findings is that it is possible to extract important information regarding the predictability of sea ice by monitoring variations in ocean heat content approximately one to three months in advance. The researchers also found evidence that heat stored in the ocean mixed layer, a thin layer of water that directly interacts with the sea ice, is a critical predictor of sea ice variability at sub-seasonal timescales.

“Studying the predictability of Arctic sea ice is a fascinating task, not only because it helps us understand the complex processes that regulate its variability, but also because of the practical implications for local communities and stakeholder groups,” says Bianco.

“As the Arctic Ocean continues to absorb solar heat during summer at a faster rate than it can release, large regions remain effectively ice-free for several months. This not only impacts indigenous communities profoundly but also carries substantial geopolitical implications due to the heightened navigability of commercially competitive Arctic shipping routes.”

More information:

Bianco, E., Iovino, D., Masina, S., Materia, S., and Ruggieri, P.: The role of upper-ocean heat content in the regional variability of Arctic sea ice at sub-seasonal timescales, The Cryosphere, 18, 2357–2379, https://doi.org/10.5194/tc-18-2357-2024, 2024.