Earth From Space: Unique Arctic Landscape Surveyed By Proba

The largest Delta in the Arctic, the Lena Delta is acomplex landscape that has evolved over thousands of years. TheHolocene (the geological era extending back from the present to thelast 10 000 years) Delta incorporates parts of an older accumulationplain, dating as far back as the mid-to-late Pleistocene Era. SamoylovIsland is located in the central southern part of the Lena Delta, closeto the Delta apex. Covering an area of 1200 hectares, it isrepresentative of the active and the Holocene part of the Delta,estimated to back about 7000 years.

Various geomorphologicallevels can be distinguished in the image. The highest terraces in theimage are determined by typical wet ice-wedge polygonal tundra withnumerous ponds and small lakes, presenting a Mid Holocene deltaicaccumulation surface of frozen fluvial permafrost deposits (dark greencolours). Two lower levels are formed by Late Holocene fluvialprocesses (light green colours) and by recent shallow and very activesandbars (whitish colours).

All terraces undergo heavy changes interms of river bank erosion, island migration or thermal erosion.Another interesting feature is the presence of river ice on somesandbanks in the lower right of the scene, which remained from thespring river ice break-up approximately two weeks earlier.

Around14% of worldwide carbon is stored in permafrost soils and sediments,and scientific interest is growing in the role of tundra environmentsin the carbon cycle. In particular tundra wetlands like the Lena Deltaare considered major contributors to the global carbon balance, andanticipated to be highly sensitive to climate change.

German-Russianresearch activity has been ongoing in the Lena Delta in the last fewyears, focusing on biology, soil sciences, ecology, paleo-environmentalinvestigations and modern environmental change. The German AlfredWegener Institute for Polar and Marine Research together with theRussian Lena Delta Reserve has placed an ecological station on SamoylovIsland, and is evaluating whether to site a permanent environmentalobservatory there.

In order to better quantify carbon budgets inthe vast Lena Delta tundra wetlands, Earth Observation is being used byresearchers to upscale local field measurements, with Proba imageshelping to validate tundra surface and vegetation unit classificationbased on Landsat-7 data.

This image was acquired on 5 July 2005by the Compact High Resolution Imaging Spectrometer (CHRIS). Built byUK-based Sira Technology, CHRIS is the main payload on ESA's Probamicrosatellite, designed to acquire hyperspectral images with a spatialresolution of 18 metres across an area of 14 kilometres.

The sizeof a washing machine, Proba was originally launched in 2001 as atechnology demonstrator, but is now operated as an ESA EarthObservation Third Party Mission.