A new dataset developed at the Nansen Center provides a detailed and long time series on the age of sea ice. This provides important knowledge for understanding changes in sea ice, improving climate models, and facilitating safer activities in northern seas.
When sea ice forms, it is thin, smooth and more vulnerable to wind and weather than thicker ice. Newly formed ice is called first-year ice. It drifts easily with the wind and currents, which leads to more openings in the ice cover. Ice that survives the summer without melting has time to grow thicker and coarser, and it becomes more robust against the effects of the atmosphere and the sea. It is then called multi-year ice. As the ice ages, it loses some of its salt, which means that it will remain frozen at higher temperatures than newer ice. These properties make the sea ice age a key indicator of how the ice cover is developing.
A rapidly changing Arctic
In recent decades, the proportion of multi-year ice in the Arctic has declined significantly, while first-year ice accounts for an increasingly large part of the ice cover. This development makes the ice more vulnerable to melting and increases the need for long, consistent data series that track developments over time. It is expected that the Arctic will be virtually ice-free during the summer months by 2050.
New data set provides more detail
Researchers at the Nansen Center and the Norwegian Meteorological Institute have recently published a dataset describing the age of sea ice in the Arctic from 1991 to 2024. The dataset is based on satellite measurements of ice concentration and ice movement. It provides a more detailed picture of both spatial patterns and long-term trends in ice development. The dataset shows the ongoing decline in multi-year ice and how first-year ice is covering increasingly larger areas. Compared to previous datasets on sea-ice age, this new dataset is more consistent with observations made from satellites.
Important tool for climate research, model development and safer waters
Sea-ice age is increasingly used in reanalyses to correct biases in sea-ice thickness reconstructions. The age of the ice is also important when researchers evaluate the ability of climate models to simulate developments in the Arctic, and when new methods for data assimilation are tested. The new dataset provides a more robust and consistent observation series, which strengthens the monitoring of sea-ice and climate conditions in the Arctic and supports efforts to understand and predict changes in the region.
An important part of the SAGE project
The dataset has been developed as part of the SAGE project, which aims to extend the time series for sea-ice age all the way back to 1980. The new research represents a first step in this work. Although the recently published series starts in 1991 and older products already describe sea-ice age back to 1980, a new approach is now being attempted that will be used in the development of a more complete time series. This will be valuable both for research purposes and for society.
Key researchers: Anton Korosov, Léo Edel, Heather Regan
