ORCID Profile
0000-0002-9389-7093
Current Organisations
University of Potsdam
,
Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences
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Publisher: American Geophysical Union (AGU)
Date: 10-2020
DOI: 10.1029/2019JF005424
Abstract: As the Arctic coast erodes, it drains thermokarst lakes, transforming them into lagoons, and, eventually, integrates them into subsea permafrost. Lagoons represent the first stage of a thermokarst lake transition to a marine setting and possibly more saline and colder upper boundary conditions. In this research, borehole data, electrical resistivity surveying, and modeling of heat and salt diffusion were carried out at Polar Fox Lagoon on the Bykovsky Peninsula, Siberia. Polar Fox Lagoon is a seasonally isolated water body connected to Tiksi Bay through a channel, leading to hypersaline waters under the ice cover. The boreholes in the center of the lagoon revealed floating ice and a saline cryotic bed underlain by a saline cryotic talik, a thin ice‐bearing permafrost layer, and unfrozen ground. The bathymetry showed that most of the lagoon had bedfast ice in spring. In bedfast ice areas, the electrical resistivity profiles suggested that an unfrozen saline layer was underlain by a thick layer of refrozen talik. The modeling showed that thermokarst lake taliks can refreeze when submerged in saltwater with mean annual bottom water temperatures below or slightly above 0°C. This occurs, because the top‐down chemical degradation of newly formed ice‐bearing permafrost is slower than the refreezing of the talik. Hence, lagoons may precondition taliks with a layer of ice‐bearing permafrost before encroachment by the sea, and this frozen layer may act as a cap on gas migration out of the underlying talik.
Publisher: Frontiers Media SA
Date: 23-07-2021
DOI: 10.3389/FEART.2021.637899
Abstract: Permafrost region subsurface organic carbon (OC) pools are a major component of the terrestrial carbon cycle and vulnerable to a warming climate. Thermokarst lagoons are an important transition stage with complex depositional histories during which permafrost and lacustrine carbon pools are transformed along eroding Arctic coasts. The effects of temperature and salinity changes during thermokarst lake to lagoon transitions on thaw history and lagoon deposits are understudied. We analyzed two 30-m-long sediment cores from two thermokarst lagoons on the Bykovsky Peninsula, Northeast Siberia, using sedimentological, geochronological, hydrochemical, and biogeochemical techniques. Using remote sensing we distinguished between a semi-closed and a nearly closed lagoon. We (1) characterized the depositional history, (2) studied the impact of marine inundation on ice-bearing permafrost and taliks, and (3) quantified the OC pools for different stages of thermokarst lagoons. Fluvial and former Yedoma deposits were found at depth between 30 and 8.5 m, while lake and lagoon deposits formed the upper layers. The electrical conductivity of the pore water indicated hypersaline conditions for the semi-closed lagoon (max: 108 mS/cm), while fresh to brackish conditions were observed beneath a 5 m-thick surface saline layer at the nearly closed lagoon. The deposits had a mean OC content of 15 ± 2 kg/m 3 , with higher values in the semi-closed lagoon. Based on the cores we estimated a total OC pool of 5.7 Mt-C for the first 30 m of sediment below five mapped lagoons on the Bykovsky Peninsula. Our results suggest that paleo river branches shaped the middle Pleistocene landscape followed by late Pleistocene Yedoma permafrost accumulation and early Holocene lake development. Afterward, lake drainage, marine flooding, and bedfast ice formation caused the saline enrichment of pore water, which led to cryotic talik development. We find that the OC-pool of Arctic lagoons may comprise a substantial inventory of partially thawed and partially refrozen OC, which is available for microbial degradation processes at the Arctic terrestrial-marine interface. Climate change in the Arctic leading to sea level rise, permafrost thaw, coastal erosion, and sea ice loss may increase the rate of thermokarst lagoon formation and thus increase the importance of lagoons as biogeochemical processors of former permafrost OC.
Publisher: Wiley
Date: 2018
Abstract: TERENO‐NE investigates the regional impact of global change. We facilitate interdisciplinary geo‐ecological research. Our data sets comprise monitoring data and geoarchives. We are able to bridge time scales from minutes to millennia. The Northeast German Lowland Observatory (TERENO‐NE) was established to investigate the regional impact of climate and land use change. TERENO‐NE focuses on the Northeast German lowlands, for which a high vulnerability has been determined due to increasing temperatures and decreasing amounts of precipitation projected for the coming decades. To facilitate in‐depth evaluations of the effects of climate and land use changes and to separate the effects of natural and anthropogenic drivers in the region, six sites were chosen for comprehensive monitoring. In addition, at selected sites, geoarchives were used to substantially extend the instrumental records back in time. It is this combination of erse disciplines working across different time scales that makes the observatory TERENO‐NE a unique observation platform. We provide information about the general characteristics of the observatory and its six monitoring sites and present ex les of interdisciplinary research activities at some of these sites. We also illustrate how monitoring improves process understanding, how remote sensing techniques are fine‐tuned by the most comprehensive ground‐truthing site DEMMIN, how soil erosion dynamics have evolved, how greenhouse gas monitoring of rewetted peatlands can reveal unexpected mechanisms, and how proxy data provides a long‐term perspective of current ongoing changes.
Publisher: Deutsches GeoForschungsZentrum GFZ
Date: 2019
Location: Germany
No related grants have been discovered for Susanne Liebner.