Summer Arctic sea ice may drive the change in Summer North Atlantic Oscillation
The Arctic has been warming at an accelerated rate in recent decades, outpacing the global average. This rapid warming is accompanied by a substantial decrease in the areal extent and by thinning of the sea ice. The transformation has piqued the interest of scientists worldwide, prompting a closer look at how these changes might be influencing weather patterns far beyond the Arctic Circle.
One key area of interest is the Summer North Atlantic Oscillation (SNAO), a weather phenomenon characterized by fluctuations in sea level pressure over the North Atlantic Ocean. The SNAO plays a crucial role in shaping the summer climates of Europe, North America, and Asia. Especially in northwestern Europe, the SNAO is closely related to summer climate extremes, including flooding, drought, and heat stress. Therefore, it is vital to understand what causes its variations and one candidate is the melting of sea ice in the Arctic
In a new study, published in Science Advances, an international research team has turned to a wealth of data, including observed sea ice concentration and sea surface temperature, global reanalysis and model simulations, to investigate the potential link between the SNAO and Arctic sea ice.
The study finds that the relationship between the SNAO and Arctic sea ice primarily originates from the East Siberian- to Arctic Canada region (ESAC), where a weak atmospheric jet stream exists in summer. This finding is supported by simulations from ocean-atmosphere coupled models.
– The main result of our study is that changes in the SNAO may be affected by variations in sea ice concentration over the ESAC region several weeks prior. The impact of ESAC sea ice concentration on the SNAO is partly due to atmospheric Rossby waves* propagating from high latitudes toward the tropics, says Tinghai Ou, one of the contributing authors and a Principal Research Engineer at the University of Gothenburg, Department of Earth Sciences.
– This means that changes in ESAC sea ice concentration may affect atmospheric circulation, specifically the jet stream, and subsequently influence the SNAO.
While these relationships were evident in observations, reanalysis, and simulations by ocean-atmosphere coupled models, they were not reproduced in simulations by atmosphere-only models forced by observed sea ice.
– The result of our study are interesting for scientists in the field as well as the public who are curious about the impact of climate change in the Arctic on mid-to-high latitude climate. The study is also important for weather prediction over the Northern Hemisphere.
The study "The Summer North Atlantic Oscillation, Arctic sea ice, and Arctic jet Rossby wave forcing" is published in Science Advances.
DOI: 10.1126/sciadv.adk6693
*Atmospheric Rossby waves form primarily as a result of the Earth's geography. Rossby waves help transfer heat from the tropics toward the poles and cold air toward the tropics in an attempt to return atmosphere to balance. They also help locate the jet stream and mark out the track of surface low pressure systems.
(Source: National Ocean Services)
Contact:
Tinghai Ou, Principal Research Engineer, University of Gothenburg, Department of Earth Sciences, tinghai.ou@gu.se
Hans Linderholm, Professor in Physical Geography, University of Gothenburg, Department of Earth Sciences, hansl@gvc.gu.se
