Sea ice in the Arctic goes through seasonal changes each year, receding to its minimum extent each September and then refreezing to its maximum extent over the winter. In recent decades, however, sea ice minimums have been getting smaller and smaller. The Arctic currently is warming at twice the rate of the rest of the world—part of a phenomenon called polar amplification—and its ice is declining by more than 10% per decade. All 10 of the lowest sea ice minimums on record have occurred since 2007.
Numerous studies have shown that as carbon dioxide emissions amplify the impact of the Sun’s radiation and sea surface temperatures warm, weather patterns shift from the tropics toward the poles. Here Zappa et al. examined how sea ice loss and polar amplification could potentially counteract these shifts.
Using the Coupled Model Intercomparison Project Phase 5 (CMIP5), the team analyzed climate simulations from 37 different models. They identified the behavior of atmospheric circulation in response to increasing carbon dioxide and sea surface warming. They compared the results to a projected scenario over a future 30-year period (2069–2099), which also includes reductions in sea ice cover.
The results of multiple models showed that sea ice loss would have an impact on atmospheric circulation in the midlatitudes (the area between the tropics and the poles) between January and March, which is when surface temperature changes related to sea ice are greatest. The researchers also found that sea ice loss would suppress the poleward shift of the North Atlantic jet stream due to climate change in late winter. It would also increase surface pressure (the weight of the atmosphere pushing down on the Earth’s surface) in northern Siberia and lower it in North America, which would have implications for regional climate.
This study is the first successful attempt to use a suite of multiple models to show the impact of sea ice loss on atmospheric circulation. With recent reports estimating that the Arctic could be entirely ice free by 2040, scientists have every motivation to learn all they can about this sensitive region. (Geophysical Research Letters, https://doi.org/10.1002/2017GL076096, 2018)
—Sarah Witman, Freelance Writer