Lena River Delta - Various Project Activities

Characteristics and spectral properties of periglacial landforms in the Lena Delta, Arctic Russia

G. Grosse (GIPL UAF), M. Ulrich, L. Schirrmeister (AWI Potsdam)

ESA (European Space Agency) provides several hyperspectral CHRIS Proba images from 3 sites in the Lena River Delta Region for this project.

The Lena River Delta is a very change sensitive region at the North Siberian land-ocean boundary and situated in the continuous permafrost zone. This sensitivity makes the Lena River Delta an important Arctic region to study early impacts of global change (permafrost degradation, coastal erosion, sea level rise, changes in fluvial discharge, land cover change, etc.). Several activities are carried out in close collaboration with the AWI Potsdam and Russian partners, to study past and modern processes in this periglacial, deltaic tundra landscape, and their impacts and feedbacks.

Investigation area

The Lena River Delta in the Laptev Sea is the largest delta in the Arctic (about 29,000 km2). It is situated in the zone of continuous permafrost, but is also characterized by widespread thermokarst. Geomorphologically, three main terraces can be distinguished. The first main terrace, including the lower and upper floodplains and the first terrace above the floodplain represents the modern active delta. The second terrace (Late Pleistocene to Early Holocene) is of fluvial genesis, but poorly influenced by fluvial processes nowadays. Relics of a Late Pleistocene accumulation plain form the third terrace.

LEDAM - Morphologic characterisation of the Lena Delta using remote sensing and terrain modelling

H. Lantuit (AWI Potsdam), G. Grosse (GIPL UAF), J. Boike, L. Schirrmeister H.-W. Hubberten (AWI Potsdam)

ESA (European Space Agency) provides numerous images from all three ALOS sensors: PRISM, AVNIR-2, and PALSAR for this study.

Abstract

Permafrost degradation, coastal processes and fluvial processes play a major role in the modification of the landscape and the environment in the second largest delta in the world.
The melting of permafrost will result in dramatic modifications of the topography. Remote sensing offers excellent possibilities to detect and map this so-called thermokarst through high resolution terrain datasets. The availability of a high-resolution DEM is thus a prerequisite for geomorphological studies and volumetric balances of matter fluxes associated with the melting of permafrost terrain.
Fluvial processes in the Lena Delta are responsible for large parts of the existing relief in this region. The Lena River releases vast quantities of sediment, ice and organic matter during spring floods which rework the existing landscape yearly. These processes occur at large scales and are hardly being monitored, mostly because of the difficulties and the costs associated with in situ measurements. A high-resolution hydrologic model of the Lena Delta would provide a greater insight into current hydrological processes, by mapping the current state of the channels and providing a baseline for future studies. A PRISM derived DEM covering the whole Delta would be a major benefit for the analysis and modelling of important hydrological processes in the Lena Delta, e.g. the inundation of large parts of the delta during the annual spring flood. The DEM would form the basis for the modelling of future changes in the run-off patterns within the Lena Delta.
The coastal zone of the Lena Delta is a highly sensible zone in the Arctic marine-terrestrial interface, and thus also an important indicator for environmental changes. Coastal erosion rates have been shown to increase in the Arctic under warming trends. However, current datasets are limited to North America and omit Russian coasts, which are concerned with similar phenomena. The lack of consistent coastal erosion rates throughout the Arctic is problematic because it impedes the assessment of clear trends. LEDAM's objective is to provide up-to-date high resolution coastal erosion datasets for the Lena Delta and to contribute those to existing Circum-Arctic projects aiming at creating a larger picture of coastal erosion in the Arctic (ACD - Arctic Coastal Dynamics and ACCO/Net - Arctic Coastal Obsevatories Network). High-resolution PRISM data will be used together with archive data for a multitemporal study of coastal dynamics in the Lena Delta. Available CORONA satellite imagery with 2.5 m ground resolution from around 1960 will help us build a record of about 45-50 years of coastal changes in the area.
Vegetation dynamics and connected fluxes (energy, greenhouse gases) are one of our major research interests in the Lena Delta. High-resolution area-wide remotely sensed datasets (AVNIR-2) will provide us with the means to analyze most of the mostly small-scale and complex tundra vegetation patterns. A Lena Delta wide vegetation study applying Landsat-7 ETM+ data was already performed at AWI Potsdam, with the goal of deriving methane emission rates from different vegetation complexes. We will use AVNIR-2 and to fill the gap between Landsat and field data in terms of scale. PALSAR data will be used in combination with high resolution terrain datasets to map soil moisture distribution. The integration of these datasets will help us refine the methodology used to map matter fluxes in the area.

Project Integration

LEDAM will be integrated with other research programmes examining the Arctic system during the upcoming International Polar Year (IPY) 2007/2008. The proposed research fits particularly well the goals and objectives of several "flagship" scientific research programmes within the IPY in detecting and elucidating the recent changes in the Arctic and their impacts. The Lena Delta has been chosen as a key site for the Arctic Coastal Dynamics (ACD) and the Arctic Circum-Polar Coastal Observatory Network (ACCO-Net) international IPY projects. LEDAM will feed in the international ESF network SEDIFLUX and other scientific and ecological programs, such as the Lena Delta Reserve (LDR, Russia and WWF), the Samoylov Ecological Research Station Lena Delta (Russia and Germany) and the Helmholtz EOS PhD-program on terrestrial carbon sources and sinks (Germany).

LEDAM will contribute to major scientific research questions:

• Dynamics of Arctic coasts under predicted climate warming
• Consequences of land cover change for Arctic ecosystems
• Behaviour of fluvial morphodynamics due to changing water cycle in the near future

Morphometry and spatial distribution of lakes in the Lena Delta, NE Siberia (Remote Sensing and GIS analyses)

A. Morgenstern (AWI Potsdam), G. Grosse (GIPL UAF), L. Schirrmeister (AWI Potsdam), H. Asche (University of Potsdam)

The Lena Delta is characterized by numerous lakes, which are important geomorphological and ecological features. Obviously, the lakes are of different genesis, e. g. thermokarst or abandoned channel lakes. Parts of the delta are dominated by oriented lakes, i. e. elongated lakes with a common, preferred long-axis orientation. Until now, only very general descriptions of the Lena Delta lakes had been available. Thus, one of the main intention of our work was to develop a detailed lake inventory and to conduct morphometric and statistical analyses on the resulting spatial dataset. Our lake dataset consisting of more than 2600 lakes with an area of >200.000 m2 was extracted from a Landsat-7 ETM+ image mosaic. Further spatial analysis was performed in vector format in a Geoinformation System (GIS).

Several morphometric variables and indices including the main axis orientation of the lakes were determined. All parameters were statistically analyzed regarding their association with the geomorphological main units of the Delta. The results show significant differences in the occurrence of lake characteristics between the delta terraces. For each terrace, a mean lake type could be distinguished, reflecting the special lithological and cryolithological conditions and geomorphological processes dominating there. Small lakes of irregular shape with strong deviations from mean orientation prevail on the first terrace. Those characteristics are typical for lakes in active floodplains like oxbow lakes and meander scrolls. On the second terrace the mean lake type is represented by large, elongated lakes with a common NNE orientation of their major axes. Lakes on the third terrace show typical features for thermokarst lakes in ice-rich permafrost, i. e. regular shorelines and little variation from circularity.

One main focus of our investigation was laid on lake orientation of the lakes on the second terrace. The phenomenon of oriented lakes, described for arctic coastal plains in Alaska, Canada and Siberia, has not been fully explained yet despite intense research during the past decades. Different theories on the cause of orientation have been proposed in the literature. The validity of these theories is discussed for the Lena Delta in the light of our results from morphometric analysis of the Lena Delta lakes and additional cryolithological data.

Characteristics and spectral properties of periglacial landforms in the Lena Delta, Arctic Russia

G. Grosse (GIPL UAF), M. Ulrich, L. Schirrmeister (AWI Potsdam)

ESA (European Space Agency) provides several hyperspectral CHRIS Proba images from 3 sites in the Lena River Delta Region for this project.