Summertime sea ice loss in the Arctic has been increasing markedly in recent decades due to human-caused global warming. For instance, in 2020 the annual minimum sea ice extent occurred on Sept. 15 and covered 3.74 million square kilometers (1.45 million square miles) – the second lowest in the 42-year satellite record.
During late summer 2020, an extreme melt event removed all sea ice from a large area north of Greenland. The absence of ice exposed the ocean surface to the atmosphere, creating a region several million square kilometers in size with an open fetch of water, rather than reflective sea ice. This rare occurrence gave scientists a chance to observe how swiftly clouds might respond to such rapid environmental changes.
With summer sunlight available around the clock in the Arctic, the researchers found that low clouds formed over the open water of the ice-free area at twice the rate observed when sea ice was present. To better understand the processes leading to increased cloudiness in the ice-free area, they examined other satellite-derived measurements along with the cloud data. They found that surface warming, water vapor, and the turbulent mixing of the atmosphere near the surface – often referred to as turbulent kinetic energy – were all enhanced in the areas with increased cloudiness.
In follow-up numerical simulations with a computer model that simulates the behavior of the Earth's climate, the researchers confirmed the critical role of surface heat storage in causing the increased cloudiness. The results underscore the sensitivity of Arctic clouds to even sudden and relatively short-lived changes in the sea ice cover, which the researchers caution could have implications for Arctic energy budget, atmospheric circulation and weather conditions in other regions.
The research was published June 29, 2022, in the journal Geophysical Research Letters.
