The weather in the Arctic matters for all of us, for two reasons. Firstly, weather is a global phenomenon, and the atmosphere in the Arctic is directly linked to weather events further south. Secondly, as the Arctic warms, sea ice cover is decreasing, changing the nature of the Arctic Ocean. To understand and predict the current changes, we need to understand the High Arctic weather, which is very tightly linked to understanding the clouds.
Our knowledge of clouds in the High Arctic is limited, but we know that one crucial part of the puzzle is the role played by tiny particles (called aerosols) that are carried by air. Aerosols are essential for cloud formation, and they affect the way that clouds reflect and scatter light. In general, they can come from lots of different places, but the air in the High Arctic is a long way from the usual aerosol sources. This means that aerosol numbers are very low, and their origin is unknown. Studies of Arctic clouds have found that they contain tiny particles of organic material that look as though they originate in the ocean, but it’s not clear how this material travels from the ocean into the air. Our study was designed to investigate one potential mechanism for transfer: the bursting of bubbles in the patches of open water between ice floes. Bubbles spit tiny droplets upwards when they burst, and previous studies have seen bubbles in the water near ice floes.
We spent two months on the icebreaker Oden, and for the majority of that time, we were moored next to a large ice floe, drifting with it close to the North Pole. On the opposite side of the floe, well away from the ship, we set up experiments to monitor an open lead (an area of open water between floes). We measured water currents, temperature, salinity and dissolved gases in order to investigate how bubbles might form. Bubbles were filmed with a specialised bubble camera that sat just below the water surface. The production of particles at the water surface was measured using a floating aerosol chamber which collected every particle ejected from an enclosed water surface. We monitored the same patch of open water for four weeks, watching what happened as the ice moved, the weather changed, and the water surface started to freeze at the end of the summer.
University College London