Lena River Delta and its hinterland

The Lena River Delta, situated on the fringe of the Laptev Sea, exhibits a size of approximately 32,000 km2 and consists of a large number of flat islands. One of them, “Samoylov Island” (72°22’N, 126°30’E), is located in the delta’s centre, provides an area of 4.3 km2 and has been hosting researchers for more than two decades. The site is characterised by a polar climate and very cold and ice-rich permafrost which thaws to a depth of 0.3-1 m annually. Moreover, the soils feature a high organic matter content, low nutrient availability and pronounced water-logging. During the growing season, usually lasting for three months, the synoptic conditions strongly vary due the location at the interface of water-land. Wind from the Arctic Ocean transports cold and moist air whereas the Siberian mainland generates warm and dry air masses. The annual mean air temperature and annual precipitation amounts to -12.5 °C and 125 mm respectively. These harsh conditions only allow the growth of sparse vegetation, predominantly comprising sedges and mosses whose distribution is determined by the underlying soil characteristics. Two geomorphological units split the island into two parts: the modern floodplain which is flooded during the annual spring flood and situated in the western part, and the late-Holocene river terrace which is represented by wet polygonal tundra and located in the eastern part.

Samoylov Island
Research station

Research objectives

Within the framework of this work package, we attempt to achieve the following objectives:

  • Quantifying the variability of greenhouse gas exchange fluxes across multiple spatial and temporal scales, based on different observation techniques
  • Characterising the climatic control of arctic carbon cycle processes
  • Evaluating the role of specific biogeochemical and ecophysiological processes in the carbon cycle of permafrost-affected ecosystems
  • Investigating lateral carbon fluxes through catchment discharge and coastal erosion
  • Developing upscaling procedures to link small-scale observations to large-scale model grids by means of remote sensing techniques
  • Investigating the human impact on permafrost landscapes

The micrometeorological eddy-covariance-method is deployed for the quantification of the land-atmosphere exchange fluxes of CO2 and CH4. Nearby the research station an eddy-covariance system on a stationary flux tower is operating on the river terrace whereas an eddy-covariance system mounted on a mobile flux tower runs on the modern floodplain. Besides the temporal variability, the arrangement of multiple measurement systems at representative landscape units is meant to gather site-specific records in order to depict the spatial variability of tundra ecosystems. The deployment of a further eddy-covariance system is envisaged in the mountainous tundra around the Lena River Delta. Since eddy-covariance measurements indicate properties of their footprints being hundreds of square meters in size, chamber measurements are also deployed in order to determine fine-scale fluxes of carbonaceous trace gases. In addition to flux measurements, standard meteorological, soil hydrological and phenological data is collected at each investigated site. This ancillary data, in conjunction with flux records, is applied for the identification of site-specific key drivers which provide a direct impact on the magnitude of the emitted carbon flux.

Stationary eddy- covariance system on late-Holocene river terrace
Mobile eddy-covariance system mounted on the floodplain

Besides the micrometeorological methods for partitioning of gathered carbon fluxes into photosynthesis and respiration, isotope chemical methods are used for, firstly, the confirmation of results gained through micrometeorological methods, secondly, the further partitioning of respiration into autotrophic and heterotrophic respiration, and thirdly, the separated balancing of methane formation and methane oxidation. For the partitioning of the net carbon flux into photosynthesis and respiration, concentrations and isotope signatures of CO2 and CH4 are determined in soil, vegetation and near-surface atmosphere by means of chamber measurements at different sampling sites. To further separate total ecosystem respiration into autotrophic and heterotrophic respiration the flux-gradients of CO2 and CH4 and the δ13CO2 signatures are measured at high intervals. These measurements are supplemented by in situ incubation experiments and 13C-pulse-labelling experiments which also provide important information on respiration fluxes and types. The analysis of δ13CH4 will further contribute crucial data to estimate the impact of the CH4 cycle on the total ecosystem respiration and on the fresh, accumulated plant material forming the source material for methanogenesis.

Chamber measurements
PVC collars for chamber measurements and gradient measurements

In addition to the vertical flux measurements between soil, vegetation and atmosphere, lateral carbon fluxes within one landscape unit as well as from a terrestrial system into the widespread system of lakes and rivers is investigated. This requires hydrological measurements of the runoff from the wet tundra into lakes and the continuation into the fluvial systems of the Lena River Delta. Furthermore, the content of dissolved and particular carbon in the lakes and rivers is analysed forming the total organic carbon content. Both quantities yield the lateral carbon flux. Another substantial discharge of carbon takes place through the erosion of permafrost sediments being rich in carbon. Hereto, the dislocation of the shoreline is surveyed over many years. Eventually, linking vertical and lateral carbon fluxes reveals the total carbon balance of the investigated area. Based on the knowledge of the carbon balance of representative landscape units, the magnitude of the flux-driving parameters and the extent of the correlation between the carbon flux and its determining parameters, the carbon balance ought to be presented for a regional scale. These results form a crucial input for global carbon cycle models.


German applicants

Prof. Dr. Lars Kutzbach, Dr. Christian Knoblauch and Prof. Dr. Eva-Maria Pfeiffer, Institute of Soil Science, Center for Earth System Research and Sustainability, Universität Hamburg, Partner in the KlimaCampus Hamburg, Hamburg

Prof. Dr. Martin Heimann, Max Planck Institute for Biogeochemistry, Jena

Russian Partners

Dr. Mikhail V. Glagolev, Moscow State University, Faculty of Soil Science, Moscow

Sergey A. Zimov, Northeast Science Station, Cherskii

Prof. Dr. Dmitry Yu. Bolshianov and Dr. Irina Federova, Arctic and Antarctic Research Institute, St. Petersburg

Dr. Mikhail N. Grigoriev,  Melnikov Permafrost Institute, Yakutsk

 

Project employees

Tim Eckhardt – PhD student, biogeochemistry

Norman Rößger - PhD student, micrometeorology

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News

Our summer school at the Ladoga Lake has just started!!

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News from the summer expedition to the delta!

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In September 2016 our "St. Petersburg summer school" for young scientists will be supported by the DAAD "Go-East Summer Schools" programme.

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Our new bilateral Master's Program CORELIS will start with the first cohort in summer 2016!

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Great photographs from our Summer School at Lake Ladoga available on-line!

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The PhD Meeting in Gülpe was a great success!

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Late summer on Samoylov Island. Read how our six scientists are going!

Scientists from Hamburg are in the Lena River Delta.

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Impressions of the Polar day, the spring flood and the ice breakup. 

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