PhD candidate
Research group | Meteorology
Main supervisor | Kirstin Krüger
Co-supervisor | Trude Storelvmo
Affiliation | Department of Geosciences, UiO
Contact | tomas.zoega@geo.uio.no
Short bio
I graduated with a B.Sc. degree in geophysics form the University of Iceland in 2016. The focus of this program was on the physics of the solid Earth but it also included elements of meteorology and oceanography. I am very interested in birding and natural conservation and following my bachelor studies, I went to Mauritius to work with the endemic pink pigeons. In 2020 I graduated with a M.Sc. degree in climate physics from the Christian-Albrecht-University in Kiel, Germany. For my final thesis I constructed a simple model describing the shortwave radiative transfer in the stratospheric aerosol layer. In the winter of 2020-2021 I studied physical geography and ecosystem modelling at the University of Lund, Sweden.
Research interests and hobbies
My research interests at the University of Oslo concern the climatic impacts of high-latitude volcanic eruptions. I will use an Earth system model with a variable grid size resolution and look at both explosive and effusive eruptions. As for hobbies, I like being outside in general and I’m very interested in literature, especially children’s literature.
CompSci project
Variable mesh earth system modelling of the climate effects of volcanic eruptions
Each year more than 50 volcanoes erupt worldwide. From those only explosive and sulfur rich volcanoes are believed to lead to significant climate signals.
High-latitude explosive eruptions have a stronger climate impact on the corresponding hemisphere than tropical eruptions with the same volcanic forcing in terms of SO2 injection into the stratosphere. Less is known on the effects of major Icelandic eruptions which can be solely emitting to the troposphere (Holuhraun 2014-2015) or can be a combination of tropospheric emissions plus explosive phases (Laki 1783-1784, Eldgjá 939).
Here we want to test the importance of applying a high resolution and variable mesh with the Community Earth System Model for the regional climate response. Commonly global climate models apply 100 to 200 km horizontal grid spacing which will be refined to a regional grid finer than 14 km resolution over the North Atlantic, Europe, and the Arctic.
This PhD project will aim for modelling the regional climate effect of major Icelandic eruptions with different SO2 emission strengths and explosivity focusing on radiation, clouds, hydrology, circulation and Earth System coupling processes at high latitudes. High Performance Computing platforms and cloud services are key for the training in computational science.
Doctoral thesis
The climate response to high-latitude effusive volcanic eruptions
Effusive volcanic eruptions are characterised by non-explosive activity. They are relatively gentle compared to their explosive counterparts, often resembling boiling stews rather than fireworks. They can impact climate through their emission of gases into the troposphere and the subsequent formation of aerosols. These aerosols, which are small particles suspended in air, reflect sunlight (shortwave radiation; SW) back to space, leading to cooling of the climate. They also interact with clouds and change their properties. This can lead to clouds reflecting more sunlight, resulting in cooling (the cloud albedo effect), but also increase their ability to trap thermal radiation from the Earth (longwave radiation; LW) close to the ground, resulting in warming (the cloud blanket effect).
In this doctoral thesis, Tómas Zoëga investigates the climate response to high-latitude, long-lasting, effusive volcanic eruptions. This is systematically explored through modelling and observational evidence. The results reveal a highly regional response with a strong seasonal dependency. In agreement with previous studies, these eruptions are found to cause cooling during summer across latitudes. During winter, however, this study finds that effusive volcanic eruptions lead to surface warming in the Arctic through enhanced trapping of terrestrial thermal radiation by thin low-level clouds under limited sunlight. These results highlight processes which play disproportionally large roles in the Arctic, such as the cloud blanket effect mentioned above, and can help us better understand this vulnerable part of the Earth system under the ongoing climate change.
Publications
CompSci publications
- Tómas Zoëga, Trude Storelvmo, and Kirstin Krüger (2025) “Modelled surface climate response to Icelandic effusive volcanic eruptions: Sensitivity to season and size” Atmospheric Chemistry and Physics 25 (5) 2989–3010
https://doi.org/10.5194/acp-25-2989-2025 | Full text in Research Archive - Tómas Zoëga, Trude Storelvmo, and Kirstin Krüger (2025) “Arctic warming from a high-latitude effusive volcanic eruption”; Scientific Reports 15 (14653)
https://doi.org/10.1038/s41598-025-98811-5 | Full text in Research Archive - Tómas Zoëga, Trude Storelvmo, and Kirstin Krüger (2025) “Climate state dependent response to very large icelandic effusive volcanic eruptions”; Geophysical Research Letters 52 (16) e2025GL114638
https://doi.org/10.1029/2025GL114638 | Full text in Research Archive
Previous publications
None yet.
