The response of Northern Hemisphere polar lows to climate change in a 25 km high-resolution global climate model

• Published in: Journal of Geophysical Research: Atmospheres
• Main Authors: Bresson, H., Hodges, K. I., Shaffrey, L. C., Zappa, G., Schiemann, R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2022
• Subjects: Climate change; North East Atlantic; Norwegian Sea; Sea ice
• Online Access: https://centaur.reading.ac.uk/97942/; https://centaur.reading.ac.uk/97942/8/JGR%20Atmospheres%20-%202022%20-%20Bresson%20-%20The%20Response%20of%20Northern%20Hemisphere%20Polar%20Lows%20to%20Climate%20Change%20in%20a%2025%20km.pdf; https://centaur.reading.ac.uk/97942/1/JGR%20Atmospheres%20-%202022%20-%20Bresson%20-%20The%20response%20of%20Northern%20Hemisphere%20polar%20lows%20to%20climate%20change%20in%20a%2025%20km.pdf

Polar lows (PLs) are small, intense cyclones that form at high latitudes during the winter. Their high wind speeds and heavy precipitation can have substantial impacts on shipping, coastal communities and infrastructure. However, low-resolution climate models poorly simulate PLs, which reduces the confidence in their future projections. In this study, Northern Hemisphere (NH) PLs are assessed for the first time in a high-resolution (25 km) global climate model, N512 HadGEM3-GA3, for both present-day and future RCP8.5 climate scenarios. The representation of PLs is found to agree reasonably well with the NCEP-CFS reanalysis. The number of NH PLs are projected to substantially decrease (by over 60%) by the end of the 21st century, which is largely due to an increase in atmospheric static stability. Large decreases in PL activity are found in the Norwegian Sea, north-east Atlantic and north-west Pacific Oceans. Smaller changes are found in regions of current PL activity, such as the Barents and Labrador Seas, while new regions of PL activity along the northern Russian coastline are found where the Arctic sea ice is projected to disappear. The spatial differences found in future PL activity could thus have a substantial impact on forthcoming activities in the Arctic region.