Studying clouds in warmer polar climates

The polar climate is changing. Annica Ekman will study feedbacks between sea ice, oceans, clouds and aerosols.

Dramatic warming and sea ice loss have been recorded at both poles during the last decade. These changes will continue at the same speed, or even increase at the end of the century if there are no drastic reductions in greenhouse gas emissions.

Annica Ekman will as a Wallenberg Scholar investigate if clouds over the polar oceans can dampen global warming and thereby also the melting of sea ice. When sea ice melts, open ocean is exposed.  A dark water surface absorbs more solar radiation than a bright ice surface and this can in turn enhance the warming of the ocean and accelerate the sea ice melt. 

One way to dampen the warming could be if clouds form over ice-free water surfaces. Clouds reflect solar radiation about as efficiently as an ice surface and can thereby to some extent prevent the warming of the sea.

Complex processes behind cloud formation

Current knowledge, which is mainly based on information from climate models, is that clouds do exactly this – dampen the global warming – or that they have a small effect on global climate. However, cloud formation in polar regions is governed by complex physical and chemical processes, and there are good reasons to believe that these are not described correctly in the models.

Annica Ekman and her research group will develop a new numerical model that describes cloud formation in detail. They will use the model together with satellite observations and measurements conducted in the Arctic and Antarctic to better understand cloud formation processes. The group will also investigate how the clouds, their extent, and their ability to reflect radiation are affected by different factors that change in a warmer climate such as the energy exchange at the ocean surface, the amount of microscopic particles in the air, and large-scale winds.

The new knowledge will be used to evaluate and improve climate models.