Extreme warm events in the South Orkney Islands, Southern Ocean: Compounding influence of atmospheric rivers and föhn conditions
Abstract Extreme warm events in the South Orkney Islands (SOIs) are investigated using synoptic observations from Signy and Orcadas stations for 1947–1994 and 1956–2019 respectively. Defining the extremes as temperatures exceeding the 95th percentile of the temperature distribution, we reveal the ch...
Published in: | Quarterly Journal of the Royal Meteorological Society |
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Online Access: | http://dx.doi.org/10.1002/qj.4578 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.4578 |
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crwiley:10.1002/qj.4578 2024-09-15T17:48:37+00:00 Extreme warm events in the South Orkney Islands, Southern Ocean: Compounding influence of atmospheric rivers and föhn conditions Lu, Hua Orr, Andrew King, John Phillips, Tony Gilbert, Ella Colwell, Steve Bracegirdle, Thomas J. British Antarctic Survey Horizon 2020 Framework Programme Natural Environment Research Council 2023 http://dx.doi.org/10.1002/qj.4578 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.4578 en eng Wiley http://creativecommons.org/licenses/by/4.0/ Quarterly Journal of the Royal Meteorological Society volume 149, issue 757, page 3645-3668 ISSN 0035-9009 1477-870X journal-article 2023 crwiley https://doi.org/10.1002/qj.4578 2024-08-20T04:17:42Z Abstract Extreme warm events in the South Orkney Islands (SOIs) are investigated using synoptic observations from Signy and Orcadas stations for 1947–1994 and 1956–2019 respectively. Defining the extremes as temperatures exceeding the 95th percentile of the temperature distribution, we reveal the characteristics and associated drivers of the warm events, especially the top 10 events in both summer and winter. At both stations, extreme warm events often involve a combined effect of atmospheric rivers (ARs) and localised föhn warming, with distinct characteristics due to the station locations relative to Coronation Island, the largest and highest island of the SOIs. For example, warm events at Signy are warmer (by an average of around 3°C) than the corresponding concurrent temperatures at Orcadas. The number of warm events per year has significantly increased over the record periods at both stations, which could potentially impact ecosystems by increasing melting of snow and ice. Extreme warm events at Signy are dominated by föhn warming in combination with ARs originating from the Southern Atlantic Ocean, where warm, moisture‐rich air is rapidly advected towards the islands by enhanced northerly winds. By contrast, the Orcadas warm extremes involve both warm‐air advection and föhn warming associated with enhanced northwesterlies/westerlies with ARs originating in the Pacific Ocean that travel across the Drake Passage. Simulation of one of the top 10 warm events for Signy station using a 1‐km grid spacing configuration of the atmosphere‐only UK Met Office Unified Model is used to disentangle the role of local versus large‐scale forcing. We find that the majority of the warming can be attributed to föhn effects for the case study. These results demonstrate the complexity of Antarctic temperature extremes. Article in Journal/Newspaper Antarc* Antarctic Coronation Island Drake Passage South Orkney Islands Southern Ocean Wiley Online Library Quarterly Journal of the Royal Meteorological Society |
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Open Polar |
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Wiley Online Library |
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crwiley |
language |
English |
description |
Abstract Extreme warm events in the South Orkney Islands (SOIs) are investigated using synoptic observations from Signy and Orcadas stations for 1947–1994 and 1956–2019 respectively. Defining the extremes as temperatures exceeding the 95th percentile of the temperature distribution, we reveal the characteristics and associated drivers of the warm events, especially the top 10 events in both summer and winter. At both stations, extreme warm events often involve a combined effect of atmospheric rivers (ARs) and localised föhn warming, with distinct characteristics due to the station locations relative to Coronation Island, the largest and highest island of the SOIs. For example, warm events at Signy are warmer (by an average of around 3°C) than the corresponding concurrent temperatures at Orcadas. The number of warm events per year has significantly increased over the record periods at both stations, which could potentially impact ecosystems by increasing melting of snow and ice. Extreme warm events at Signy are dominated by föhn warming in combination with ARs originating from the Southern Atlantic Ocean, where warm, moisture‐rich air is rapidly advected towards the islands by enhanced northerly winds. By contrast, the Orcadas warm extremes involve both warm‐air advection and föhn warming associated with enhanced northwesterlies/westerlies with ARs originating in the Pacific Ocean that travel across the Drake Passage. Simulation of one of the top 10 warm events for Signy station using a 1‐km grid spacing configuration of the atmosphere‐only UK Met Office Unified Model is used to disentangle the role of local versus large‐scale forcing. We find that the majority of the warming can be attributed to föhn effects for the case study. These results demonstrate the complexity of Antarctic temperature extremes. |
author2 |
British Antarctic Survey Horizon 2020 Framework Programme Natural Environment Research Council |
format |
Article in Journal/Newspaper |
author |
Lu, Hua Orr, Andrew King, John Phillips, Tony Gilbert, Ella Colwell, Steve Bracegirdle, Thomas J. |
spellingShingle |
Lu, Hua Orr, Andrew King, John Phillips, Tony Gilbert, Ella Colwell, Steve Bracegirdle, Thomas J. Extreme warm events in the South Orkney Islands, Southern Ocean: Compounding influence of atmospheric rivers and föhn conditions |
author_facet |
Lu, Hua Orr, Andrew King, John Phillips, Tony Gilbert, Ella Colwell, Steve Bracegirdle, Thomas J. |
author_sort |
Lu, Hua |
title |
Extreme warm events in the South Orkney Islands, Southern Ocean: Compounding influence of atmospheric rivers and föhn conditions |
title_short |
Extreme warm events in the South Orkney Islands, Southern Ocean: Compounding influence of atmospheric rivers and föhn conditions |
title_full |
Extreme warm events in the South Orkney Islands, Southern Ocean: Compounding influence of atmospheric rivers and föhn conditions |
title_fullStr |
Extreme warm events in the South Orkney Islands, Southern Ocean: Compounding influence of atmospheric rivers and föhn conditions |
title_full_unstemmed |
Extreme warm events in the South Orkney Islands, Southern Ocean: Compounding influence of atmospheric rivers and föhn conditions |
title_sort |
extreme warm events in the south orkney islands, southern ocean: compounding influence of atmospheric rivers and föhn conditions |
publisher |
Wiley |
publishDate |
2023 |
url |
http://dx.doi.org/10.1002/qj.4578 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.4578 |
genre |
Antarc* Antarctic Coronation Island Drake Passage South Orkney Islands Southern Ocean |
genre_facet |
Antarc* Antarctic Coronation Island Drake Passage South Orkney Islands Southern Ocean |
op_source |
Quarterly Journal of the Royal Meteorological Society volume 149, issue 757, page 3645-3668 ISSN 0035-9009 1477-870X |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1002/qj.4578 |
container_title |
Quarterly Journal of the Royal Meteorological Society |
_version_ |
1810290068809580544 |