MOSAiC: A Year-Long City on Sea Ice

The Arctic Ocean is complicated, important and undergoing rapid climate change. As the sea ice thins and retreats, sunlight and Arctic winds are warming and stirring the ocean in an unprecedented way. This has serious implications for regional ecosystems, northern hemisphere weather and global climate.

Today I leave for the shrinking ice aboard Russian icebreaker Akademik Federov to help build a “city on ice”. The formal name for the city is the Multidisciplinary Observatory for the Study of Arctic Climate - MOSAiC for short. Its “downtown” will be the German research vessel RV Polarstern.

German icebreaker RV Polarstern will form the centerpiece of the drifting climate observatory.

Stacked full of food, fuel and scientists, Polarstern will be deliberately frozen into the sea ice for a full year in order to monitor the environment.

Surrounding the ship will be the largest array of technical instruments ever assembled on the sea ice in a historic, multimillion pound, multinational research endeavour.

MOSAiC has taken most of a decade to plan and prepare for. It represents the largest expedition to the central Arctic in history (by some margin!)

I’ll help set up and deploy these instruments and also participate in perhaps the greatest graduate summer school ever conceived: twenty PhD students will live, work and learn alongside science journalists and communicators, thrashing out the details of the Arctic climate system with the help of the MOSAiC scientists. But freezing a ship into the ice for a year isn’t easy or cheap. It requires an enormous amount of planning and money: 600 scientists from 19 countries will contribute to the 390 day expedition at a cost of more than €140m. So why bother?

We need to do this because the Arctic is the epicenter of climate change. Due to a phenomenon known as Arctic amplification, the region has seen a rise in temperature unparalleled anywhere else on the globe.

This shocking rise is forecast to continue as the world warms over the next century. Given that the Arctic drives much of Northern Hemisphere weather and sets global temperatures through its high reflectivity, this change in climate is extremely concerning. To compound our concern, scientific uncertainty abounds in the Arctic. While all mainstream climate models predict an unparallelled warming in the Arctic, inadequate representation of sea ice and cloud physics leads to large variation between the models with respect to size of the change. 

Observed change of temperature 1970 – 2017 [Degrees C]. The Arctic region has experienced unparalleled warming in recent years.

Observed change of temperature 1970 – 2017 [Degrees C]. The Arctic region has experienced unparalleled warming in recent years.

The data taken during MOSAiC’s operation will change the face of Arctic climate science and hopefully radically reduce these uncertainties. My research into the properties of snow on sea ice will be propelled forward as the expedition generates insight into how the internal properties of the snow-pack evolve. The complex issue of Arctic clouds and boundary-layer processes will be tackled head-on with measurements never before taken in the central arctic. All these measurements will ultimately be fed back into climate models and improve our understanding and predictions of future climate change.

A MOSAiC researcher practices with a tethered weather observation balloon in Svalbard

Polar scientists now frequently refer to the “New Arctic” - one characterised by diminished sea ice which is starkly younger and thinner than before. Understanding the New Arctic may require a New Science, one that’s multidisciplinary and multinational; this what we hope MOSAiC will be.

For more information, you can visit

To track the expedition as it’s built and as it drifts, visit

To read even more, visit (I wrote the original article!)