A novel approach for the characterization of tundra wetland regions with C-band SAR satellite data

A circumpolar representative and consistent wetland map is required for a range of applications ranging from upscaling of carbon fluxes and pools to climate modelling and wildlife habitat assessment. Currently available data sets lack sufficient accuracy and/or thematic detail in many regions of the Arctic. Synthetic aperture radar (SAR) data from satellites have already been shown to be suitable for wetland mapping. Envisat Advanced SAR (ASAR) provides global medium-resolution data which are examined with particular focus on spatial wetness patterns in this study. It was found that winter minimum backscatter values as well as their differences to summer minimum values reflect vegetation physiognomy units of certain wetness regimes. Low winter backscatter values are mostly found in areas vegetated by plant communities typically for wet regions in the tundra biome, due to low roughness and low volume scattering caused by the predominant vegetation. Summer to winter difference backscatter values, which in contrast to the winter values depend almost solely on soil moisture content, show expected higher values for wet regions. While the approach using difference values would seem more reasonable in order to delineate wetness patterns considering its direct link to soil moisture, it was found that a classification of winter minimum backscatter values is more applicable in tundra regions due to its better separability into wetness classes. Previous approaches for wetland detection have investigated the impact of liquid water in the soil on backscatter conditions. In this study the absence of liquid water is utilized. Owing to a lack of comparable regional to circumpolar data with respect to thematic detail, a potential wetland map cannot directly be validated; however, one might claim the validity of such a product by comparison with vegetation maps, which hold some information on the wetness status of certain classes. It was shown that the Envisat ASAR-derived classes are related to wetland classes of conventional vegetation maps, indicating its applicability; 30% of the land area north of the treeline was identified as wetland while conventional maps recorded 1–7%.

[1]  Donald A. Walker,et al.  Conservation of Arctic Flora and Fauna (CAFF) Map No. 1. , 2003 .

[2]  Sang-Eun Park,et al.  ASCAT Surface State Flag (SSF): Extracting Information on Surface Freeze/Thaw Conditions From Backscatter Data Using an Empirical Threshold-Analysis Algorithm , 2012, IEEE Transactions on Geoscience and Remote Sensing.

[3]  W. Wagner,et al.  A Method for Estimating Soil Moisture from ERS Scatterometer and Soil Data , 1999 .

[4]  Martin O. Jeffries,et al.  Ice characteristics and processes, and remote sensing of frozen rivers and lakes , 2013 .

[5]  W. Wagner,et al.  Global monitoring of wetlands--the value of ENVISAT ASAR Global mode. , 2009, Journal of environmental management.

[6]  Wolfgang Wagner,et al.  Development of a Global Backscatter Model in support to the Sentinel-1 mission design , 2012 .

[7]  Catherine Prigent,et al.  An attempt to quantify the impact of changes in wetland extent on methane emissions on the seasonal and interannual time scales , 2010 .

[8]  Martin O. Jeffries,et al.  A Method To Determine Lake Depth and Water Availability on the North Slope of Alaska with Spaceborne Imaging Radar and Numerical Ice Growth Modelling , 1996 .

[9]  Annett Bartsch,et al.  Detection of snow surface thawing and refreezing in the Eurasian Arctic with QuikSCAT: implications for reindeer herding. , 2010, Ecological applications : a publication of the Ecological Society of America.

[10]  Richard K. Moore,et al.  Radar remote sensing and surface scattering and emission theory , 1986 .

[11]  Claude R. Duguay,et al.  Response of ice cover on shallow lakes of the North Slope of Alaska to contemporary climate conditions (1950–2011): radar remote-sensing and numerical modeling data analysis , 2013 .

[12]  Bicheron Patrice,et al.  GlobCover - Products Description and Validation Report , 2008 .

[13]  Reiner Zimmermann,et al.  Satellite microwave remote sensing of North Eurasian inundation dynamics: development of coarse-resolution products and comparison with high-resolution synthetic aperture radar data , 2010 .

[14]  Birgit Heim,et al.  Water Body Distributions Across Scales: A Remote Sensing Based Comparison of Three Arctic Tundra Wetlands , 2013, Remote. Sens..

[15]  Stephen L. Durden,et al.  Differentiating methane source areas in Arctic environments with multitemporal ERS-1 SAR data , 1996, IEEE Trans. Geosci. Remote. Sens..

[16]  Klaus Scipal.  USING ENVISAT SCANSAR DATA FOR CHARACTERISING SCALING PROPERTIES O F SCATTEROMETER DERIVED SOIL MOISTURE INFORMATION OVER SOUTHERN AFRICA , 2007 .

[17]  Wolfgang Wagner,et al.  Using ENVISAT ASAR Global Mode Data for Surface Soil Moisture Retrieval Over Oklahoma, USA , 2009, IEEE Transactions on Geoscience and Remote Sensing.

[18]  Claude R. Duguay,et al.  Determining depth and ice thickness of shallow sub-Arctic lakes using space-borne optical and SAR data , 2003 .

[19]  Annett Bartsch,et al.  Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions , 2014, Remote. Sens..

[20]  John S. Kimball,et al.  Surface water inundation in the boreal-Arctic: potential impacts on regional methane emissions , 2014 .

[21]  Robert N. Colwell,et al.  Manual of remote sensing , 1983 .

[22]  Donald A. Walker,et al.  The Circumpolar Arctic Vegetation Map: AVHRR-derived base maps, environmental controls, and integrated mapping procedures , 2002 .

[23]  P. Ciais,et al.  Permafrost carbon-climate feedbacks accelerate global warming , 2011, Proceedings of the National Academy of Sciences.

[24]  Annett Bartsch,et al.  Capability of C-Band SAR for Operational Wetland Monitoring at High Latitudes , 2012, Remote. Sens..

[25]  E. S. Melnikov,et al.  The Circumpolar Arctic vegetation map , 2005 .

[26]  Yann Kerr,et al.  Soil Moisture , 1922, Botanical Gazette.

[27]  M. S. Moran,et al.  Soil moisture evaluation using multi-temporal synthetic aperture radar (SAR) in semiarid rangeland , 2000 .

[28]  Guido Grosse,et al.  Modern thermokarst lake dynamics in the continuous permafrost zone, northern Seward Peninsula, Alaska , 2011 .

[29]  M. Hansen,et al.  Vegetation Cover in the Eurasian Arctic: Distribution, Monitoring, and Role in Carbon Cycling , 2010 .

[30]  Birgit Heim,et al.  Subpixel heterogeneity of ice-wedge polygonal tundra: a multi-scale analysis of land cover and evapotranspiration in the Lena River Delta, Siberia , 2012 .

[31]  A. J. Dolman,et al.  Spatial and temporal dynamics in eddy covariance observations of methane fluxes at a tundra site in Northeastern Siberia , 2011 .

[32]  Guido Grosse,et al.  Land cover classification of tundra environments in the Arctic Lena Delta based on Landsat 7 ETM+ data and its application for upscaling of methane emissions , 2009 .

[33]  F. Aires,et al.  Global inundation dynamics inferred from multiple satellite observations, 1993–2000 , 2007 .

[34]  Yoshio Yamaguchi,et al.  Monitoring freeze/thaw cycles using ENVISAT ASAR Global Mode , 2011 .

[35]  Dirk Pflugmacher,et al.  Comparison and assessment of coarse resolution land cover maps for Northern Eurasia , 2011 .

[36]  S. Durden,et al.  Classification of radar imagery over boreal regions for methane exchange studies , 1996 .

[37]  Yann Kerr,et al.  Soil moisture retrieval from space: the Soil Moisture and Ocean Salinity (SMOS) mission , 2001, IEEE Trans. Geosci. Remote. Sens..

[38]  Klaus Scipal,et al.  An Improved Soil Moisture Retrieval Algorithm for ERS and METOP Scatterometer Observations , 2009, IEEE Transactions on Geoscience and Remote Sensing.

[39]  Annett Bartsch,et al.  Detection of open water dynamics with ENVISAT ASAR in support of land surface modelling at high latitudes , 2012 .

[40]  Klaus Scipal,et al.  Detection of permanent open water surfaces in central Siberia with ENVISAT ASAR wide swath data with special emphasis on the estimation of methane fluxes from tundra wetlands , 2008 .

[41]  Mahta Moghaddam,et al.  Mapping vegetated wetlands of Alaska using L-band radar satellite imagery , 2009 .

[42]  P. Döll,et al.  Development and validation of a global database of lakes, reservoirs and wetlands , 2004 .

[43]  A. J. Dolman,et al.  Soil carbon in the Artic and the permafrost carbon feedback , 2012 .

[44]  F. Henderson,et al.  Principles and Applications of Imaging Radar , 1998 .

[45]  R. Latifovic,et al.  Development of a circa 2000 land cover map of northern Canada at 30 m resolution from Landsat , 2009 .

[46]  Wolfgang Wagner,et al.  ASCAT Soil Moisture: An Assessment of the Data Quality and Consistency with the ERS Scatterometer Heritage , 2009 .

[47]  Niko E. C. Verhoest,et al.  Correlation between Ground Measured Soil Moisture and RADARSAT-1 derived Backscattering Coefficient over an Agricultural Catchment of Navarre (North of Spain) , 2005 .

[48]  Claude R. Duguay,et al.  Remote sensing of permafrost and seasonally frozen ground , 2013 .