Naima El Bani Altuna will publically defend her PhD thesis entitled, ‘Millennial-scale variability of Atlantic water inflow in the northern Nordic Seas and the northwestern Barents Sea – Relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor’ on September 17th 2021 at UiT – The Arctic University of Norway. This work was funded by the Centre for Arctic Gas Hydrate, Environment, and Climate (CAGE) at UiT.
Popular science abstract
Climate change is increasing Arctic air-temperatures very fast – twice as fast the rest of the world’s temperature. This is also affecting the ocean at high latitudes, where powerful greenhouse gases are stored in the seafloor trapped in ice-like cages (known as gas hydrates), that can melt if the temperature of the ocean increases. To understand how the ocean and the climate are connected, in this thesis we looked back in time to periods of rapid climate change during the last ice age, when temperature increased at a similar rate as modern. For that purpose, we studied the evolution of warm Atlantic water entering the northern Nordic Seas and the western Barents Sea using the chemical composition of shells of benthic foraminifera (microscopic single-celled organisms living in the seafloor).
In the northern Nordic Seas, we have also reconstructed sea-ice variability. We found that during cold atmospheric periods the ocean was warm (up to 5°C) because meltwater released from icebergs, and a sea-ice “lid” formed by the cold temperatures trapped the heat beneath. Instead, during warm periods the seafloor remained cooler with similar temperatures to modern. Furthermore, our work shows that both the disappearance of the sea-ice “lid” and the decrease of oceanic temperatures happened at the same time during the cold periods, which suggest a strong connection between both parameters. In the Barents Sea we focused on investigating the effect of the inflow of warm Atlantic water on gas hydrates in the seafloor. The Atlantic water did indeed affect the stability of gas hydrates, enhancing the melting of these compounds and causing the release of gas from the seafloor to the water column.
This study has improved our understanding of how the past inflow of warmer Atlantic water connects to past abrupt climate changes. Additionally, it has shed light on the relationship between Atlantic water and the stability of gas hydrates.
The plan for Naima El Bani Altuna public defense for the PhD degree in Science, on September 17th 2021, is as follows:
Trial lecture at 13:15 on the following topic:
‘Gas hydrate seeps – their impact on climate and interaction with ocean temperatures through time’
PhD thesis defense at 15:15:
‘Millennial-scale variability of Atlantic water inflow in the northern Nordic Seas and the northwestern Barents Sea – Relationship to abrupt climate oscillations, cryosphere and methane seepage from the seafloor’
PhD Thesis is published and available here.
· Professor Tine L. Rasmussen, Department of Geosciences, UiT (main supervisor)
· Researcher Dr. Mohamed Ezat, Department of Geosciences, UiT
· Professor Dr. Marit-Solveig Seidenkrantz, Department of Geoscience, Aarhus University, Denmark (1. opponent)
· Senior Research Associate Dr. Anne Jennings, University of Colorado Boulder, USA (2. opponent)
· Researcher Dr. Amando Putra Ersaid Lasabuda, Department of Geosciences, UiT (internal member and leader of the committee)
Left to Right: Professor Dr. Marit-Solveig Seidenkrantz, Researcher Dr. Amando Putra Ersaid Lasabuda, Dr Naima El Bani Altuna, Professor Tine L. Rasmussen, and Researcher Dr. Mohamed Ezat
To find out more about the findings of this research:
El bani Altuna, N., Ezat, M. M., Greaves, M., & Rasmussen, T. L. (2021). Millennial-scale changes in bottom water temperature and water mass exchange through the Fram Strait 79°N, 63-13 ka. Paleoceanography and Paleoclimatology, 36, e2020PA004061. https://doi.org/10.1029/2020PA004061
El bani Altuna, N., Rasmussen, T.L., Ezat, M.M. et al. Deglacial bottom water warming intensified Arctic methane seepage in the NW Barents Sea. Commun Earth Environ 2, 188 (2021). https://doi.org/10.1038/s43247-021-00264-x