Changing low pressure tracks in the high Arctic in winter

AGF-350/850 fieldwork in February. Photo: Matthias Gottschalk.

Top image: Siiri Wickström on fieldwork in early February 2016. Photo: Matthias Gottschalk.

Siiri Wickström has studied the regional changes in the atmospheric flow pattern in the high latitude North Atlantic and their impacts locally over Svalbard. The ongoing climate change is amplified at the high latitudes and Svalbard is a hotspot of warming, especially in the winters, Wickström concludes in her PhD thesis, which she will defend digitally on 19 May 2020.

14 May 2020
Press release from the University Centre in Svalbard (UNIS) and University of Bergen

Low pressure systems (or cyclones) are a central mechanism of atmospheric poleward heat, moisture and momentum transport. These cyclones, that are associated with bad weather- clouds, rain and wind, travel along cyclone tracks. Svalbard is located at the end of the North Atlantic Cyclone track and, hence, the location and strength has a large impact on the regional weather and climate.

Using an automatic cyclone tracking algorithm, counting low pressure centres in time and space, Wickström and her co-authors fond a significant increase in winter low pressure activity around Svalbard. The results suggest a shift towards a more north-south oriented cyclone track over the period 1979-2016. This increase is found to be connected to anomalously warm and wet winter conditions over Svalbard. Using high-resolution model data in combination with observations, these temperature and precipitation increases are found not to be evenly distributed over the archipelago, where the northern part is warming at rates close to double of that found in the southwestern parts. A consequence of warm and wet winters is rain-on-snow (ROS) events with potentially devastating societal and ecological implication. In Wickströms PhD research she finds that ROS is a common and widespread phenomenon in Svalbard’s current climate.

Siiri Wickström will defend her PhD dissertation entitled “Warmer and Wetter Winters over the high-latitude North Atlantic – an atmospheric circulation perspective” UNIS on 19 May 2020 at 10:15. She will hold a trial lecture entitled “Cold air outbreaks and polar lows” on 18 May at 10:15.

Both the disputation and the trial lecture will be done digitally on Teams. This is the first digital PhD disputation at UNIS.

The committee consists of:
Committee leader: Professor Eva Falck, University of Bergen and UNIS
First opponent: Associate professor Anna Sjöblom, Uppsala University
Second opponent: Associate professor Tim Wollings, Oxford University

Dissertation leader: Professor Asgeir Sorteberg, University of Bergen

Wickströms PhD work has been supervised by Marius O. Jonassen (UNIS/UiB) as her main supervisor and Timo Vihma (Finnish Meteorological Institute/UNIS) as the co-supervisor.

Siiri Wickström
Siiri Wickström. Photo: Eva Therese Jenssen/UNIS.

About the candidate:
Siiri Wickström was born in Oulu, Finland in 1989 and holds a Master of science degree in atmospheric physics from the University of Helsinki, Finland.

She moved to Svalbard in 2016 to start her PhD studies at the University Centre in Svalbard (UNIS). Except for shorter research visits to the Finnish Meteorological Institute and the University of Colorado, USA, she has been working in Svalbard full time during the whole PhD period.


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