Current research topics: 

1.  Method development of radiocarbon dating for submarine groundwater: by measuring carbon-13 and carbon-14 isotopes for the different carbon pooles in marine sediments we aim to close the local isotope mass balance whereby submarine groundwater can be accurately dated. 
2.  Identifying the drivers of offshore freshwater discharge in cryosphere influenced regions: by using geochemical tracers and previously discussed dating methods we aim to attribute observed submarine groundwater discharge (SGD) in the Arctic to its drivers. 
3.  Assessing the implications, extent and timescale of SGD: by deploying a numerical model we aim to simulate the process of SGD along a 2D transect to determine the physical drivers and the spatial and temporal scales on which they act. Moreover, we aim to resolve the impact of SGD on ocean chemistry and the biogeochemical cycling of elements. 

 

Past research topics:

•  Isotopic signals in atmospheric molecular hydrogen, methane and carbon monoxide and their relation to biomass burning and stratopheric processes: samples from the Atmospheric Tomography Mission were analysed and the distribution of molecular hydrogen in the atmosphere was studied. Moreover, biomass source signatures were determined and spatial differences in the stratospheric aging of air was studied.
•  The distribution of nanoplastic in the North Atlantic subtropical gyre (master dissertation): ocean water samples were collected during a 4 week research cruise through the North Atlantic subtropical gyre. The samples were analysed by using Thermal Desorption - Proton Transfer Reaction - Mass Spectrometry and fingerprinting algorithms were used on the resulting mass spectra to detect nanoplastic. 
•  The impact of global warming on the volume change of glaciers (bachelor dissertation): a glacier model using volume-area scaling was deployed, to assess the ensemble mean metre sea level rise equivalent for different RCP scenarios.

A selection from Stockholm University publication database

• Ebullition dominates methane emissions in stratified coastal waters

  2024. Martijn Hermans (et al.). Science of the Total Environment 945

  Article

  Coastal areas are an important source of methane (CH4). However, the exact origins of CH4 in the surface waters of coastal regions, which in turn drive sea-air emissions, remain uncertain. To gain a comprehensive understanding of the current and future climate change feedbacks, it is crucial to identify these CH4 sources and processes that regulate its formation and oxidation. This study investigated coastal CH4 dynamics by comparing water column data from six stations located in the brackish Tvärminne Archipelago, Baltic Sea. The sediment biogeochemistry and microbiology were further investigated at two stations (i.e., nearshore and offshore). These stations differed in terms of stratification, bottom water redox conditions, and organic matter loading. At the nearshore station, CH4 diffusion from the sediment into the water column was negligible, because nearly all CH4 was oxidized within the upper sediment column before reaching the sediment surface. On the other hand, at the offshore station, there was significant benthic diffusion of CH4, albeit the majority underwent oxidation before reaching the sediment-water interface, due to shoaling of the sulfate methane transition zone (SMTZ). The potential contribution of CH4 production in the water column was evaluated and was found to be negligible. After examining the isotopic signatures of δ13C-CH4 across the sediment and water column, it became apparent that the surface water δ13C-CH4 values observed in areas with thermal stratification could not be explained by diffusion, advective fluxes, nor production in the water column. In fact, these values bore a remarkable resemblance to those detected below the SMTZ. This supports the hypothesis that the source of CH4 in surface waters is more likely to originate from ebullition than diffusion in stratified brackish coastal systems.

  Read more about Ebullition dominates methane emissions in stratified coastal waters

Show all publications by Sophie ten Hietbrink at Stockholm University