Sea-ice observation: It’s all in the details

Dr Lars Kaleschke, sea-ice physicists at the Alfred Wegener Institute.

Sea ice

Remote Sensing

Sea ice observation systems

Sea ice plays an important role in the global climate system. It reflects changes in the system as a whole, and interconnects its subsystems. As a boundary layer between the ocean and atmosphere sea ice modulates the flow of energy, kinetic force, salt, moisture and trace gases between the two components. Though our knowledge of the sea ice in the Arctic and Antarctic is constantly growing, we still don’t understand all the connections and phenomena.

Two examples: because the thickness of the Arctic sea ice is steadily declining and meltwater pools are increasingly forming in summer, covering large areas of the Arctic sea ice, both the ice and the ocean below absorb more solar radiation. As a result, more algae grow, marine biomass production increases and more carbon is taken up and fixed. But what impact do such developments have on the sea ice itself? Are there feedbacks that could even have a positive effect on the ice cover?
In the Antarctic we’re not seeing any clear trend in sea-ice development. In addition, large ice-free areas – so-called polynyas – frequently form in the Antarctic sea ice. In the coastal polynyas, strong winds drive the sea ice away from the coast; in these ‘ice factories’ new sea ice is constantly formed, while the ice’s point of origin remains ice-free. Other phenomena – like undersea mountain ranges – can make it more likely that polynyas form far from the shore. But exactly why they form is still only poorly understood. We’re still lacking the detailed information that would allow us to understand these interactions, which also explains why they aren’t included in climate models.

In order to move forward, we need to expand our sea-ice observation systems and ask ourselves which parameters are most productive when it comes to monitoring the fluxes and changes involved. With the help of this data, we’ll be able to understand the individual processes, and to model them. The next step will be to determine which types of real-world data are needed in order to validate our computer models and depict the realities of sea ice in the Arctic and Antarctic as precisely as possible using computers. If we succeed in this detail work, we’ll also be able to improve the major climate models, so that our projections yield more accurate insights into the future of the sea ice and how its fate will affect the Earth’s climate.