Publications by authors named "Denis Kosmach"
Article Synopsis
- Subsea permafrost is a significant carbon storage area that could potentially release greenhouse gases as it thaws, but there is limited observational data leading to uncertainties about its impact.
- Five cores from the Laptev Sea were analyzed to assess organic carbon storage, degradation, and greenhouse gas production, revealing a history of sediment deposition over 160,000 years from both forest and tundra sources.
- The study estimates a thaw rate of 1.3 kg of organic carbon per square meter annually in subsea permafrost, which is much higher than terrestrial permafrost, and measured methane and carbon dioxide production during incubation, providing insight into subsea permafrost's role in ocean carbon dynamics.
The main objectives of this work were the acquisition of new data on floating marine macro litter (FMML) and natural floating objects in the Arctic seas, an initial assessment of the level of pollution by FMML and an analysis of potential sources. The results of this study present the first data on FMML distribution in Russian Arctic shelf seas in relation to oceanographic conditions (i.e.
View Article and Find Full Text PDFThe East Siberian Arctic Shelf holds large amounts of inundated carbon and methane (CH). Holocene warming by overlying seawater, recently fortified by anthropogenic warming, has caused thawing of the underlying subsea permafrost. Despite extensive observations of elevated seawater CH in the past decades, relative contributions from different subsea compartments such as early diagenesis, subsea permafrost, methane hydrates, and underlying thermogenic/ free gas to these methane releases remain elusive.
View Article and Find Full Text PDFArticle Synopsis
- * New research indicates that the ice-bonded permafrost in the ESAS has been moving downward by approximately 14 cm each year over the last 31-32 years, contradicting earlier beliefs about long-term stability post-inundation.
- * The presence of thermokarst patterns and gas migration suggests ongoing changes in the subsea environment, highlighting the need to understand permafrost degradation to predict future methane release accurately.
Sustained release of methane (CH(4)) to the atmosphere from thawing Arctic permafrost may be a positive and significant feedback to climate warming. Atmospheric venting of CH(4) from the East Siberian Arctic Shelf (ESAS) was recently reported to be on par with flux from the Arctic tundra; however, the future scale of these releases remains unclear. Here, based on results of our latest observations, we show that CH(4) emissions from this shelf are likely to be determined by the state of subsea permafrost degradation.
View Article and Find Full Text PDFRemobilization to the atmosphere of only a small fraction of the methane held in East Siberian Arctic Shelf (ESAS) sediments could trigger abrupt climate warming, yet it is believed that sub-sea permafrost acts as a lid to keep this shallow methane reservoir in place. Here, we show that more than 5000 at-sea observations of dissolved methane demonstrates that greater than 80% of ESAS bottom waters and greater than 50% of surface waters are supersaturated with methane regarding to the atmosphere. The current atmospheric venting flux, which is composed of a diffusive component and a gradual ebullition component, is on par with previous estimates of methane venting from the entire World Ocean.
View Article and Find Full Text PDF