Lantuit H.,Alfred Wegener Institute for Polar and Marine Research |
Overduin P.P.,Alfred Wegener Institute for Polar and Marine Research |
Couture N.,Geological Survey of Canada |
Wetterich S.,Alfred Wegener Institute for Polar and Marine Research |
And 20 more authors.
Estuaries and Coasts | Year: 2012
Arctic permafrost coasts are sensitive to changing climate. The lengthening open water season and the increasing open water area are likely to induce greater erosion and threaten community and industry infrastructure as well as dramatically change nutrient pathways in the near-shore zone. The shallow, mediterranean Arctic Ocean is likely to be strongly affected by changes in currently poorly observed arctic coastal dynamics. We present a geomorphological classification scheme for the arctic coast, with 101,447 km of coastline in 1,315 segments. The average rate of erosion for the arctic coast is 0.5 m year -1 with high local and regional variability. Highest rates are observed in the Laptev, East Siberian, and Beaufort Seas. Strong spatial variability in associated database bluff height, ground carbon and ice content, and coastline movement highlights the need to estimate the relative importance of shifting coastal fluxes to the Arctic Ocean at multiple spatial scales. © 2011 Coastal and Estuarine Research Federation.
Janout M.A.,Alfred Wegener Institute for Polar and Marine Research |
Aksenov Y.,UK National Oceanography Center |
Holemann J.A.,Alfred Wegener Institute for Polar and Marine Research |
Rabe B.,Alfred Wegener Institute for Polar and Marine Research |
And 9 more authors.
Journal of Geophysical Research C: Oceans | Year: 2015
Siberian river water is a first-order contribution to the Arctic freshwater budget, with the Ob, Yenisey, and Lena supplying nearly half of the total surface freshwater flux. However, few details are known regarding where, when, and how the freshwater transverses the vast Siberian shelf seas. This paper investigates the mechanism, variability, and pathways of the fresh Kara Sea outflow through Vilkitsky Strait toward the Laptev Sea. We utilize a high-resolution ocean model and recent shipboard observations to characterize the freshwater-laden Vilkitsky Strait Current (VSC), and shed new light on the little-studied region between the Kara and Laptev Seas, characterized by harsh ice conditions, contrasting water masses, straits, and a large submarine canyon. The VSC is 10-20 km wide, surface intensified, and varies seasonally (maximum from August to March) and interannually. Average freshwater (volume) transport is 500 ± 120 km3 a-1 (0.53 ± 0.08 Sv), with a baroclinic flow contribution of 50-90%. Interannual transport variability is explained by a storage-release mechanism, where blocking-favorable summer winds hamper the outflow and cause accumulation of freshwater in the Kara Sea. The year following a blocking event is characterized by enhanced transports driven by a baroclinic flow along the coast that is set up by increased freshwater volumes. Eventually, the VSC merges with a slope current and provides a major pathway for Eurasian river water toward the western Arctic along the Eurasian continental slope. Kara (and Laptev) Sea freshwater transport is not correlated with the Arctic Oscillation, but rather driven by regional summer pressure patterns. © 2015. American Geophysical Union. All Rights Reserved.
Ver Hoef J.M.,National Oceanic and Atmospheric Administration |
Ver Hoef J.M.,International Arctic Research Center |
Jansen J.K.,National Oceanic and Atmospheric Administration
Journal of Agricultural, Biological, and Environmental Statistics | Year: 2015
Monitoring plant and animal populations is an important goal for both academic research and management of natural resources. Successful management of populations often depends on obtaining estimates of their mean or total over a region. The basic problem considered in this paper is the estimation of a total from a sample of plots containing count data, but the plot placements are spatially irregular and non-randomized. Our application had counts from thousands of irregularly spaced aerial photo images. We used change-of-support methods to model counts in images as a realization of an inhomogeneous Poisson process that used spatial basis functions to model the spatial intensity surface. The method was very fast and took only a few seconds for thousands of images. The fitted intensity surface was integrated to provide an estimate from all unsampled areas, which is added to the observed counts. The proposed method also provides a finite area correction factor to variance estimation. The intensity surface from an inhomogeneous Poisson process tends to be too smooth for locally clustered points, typical of animal distributions, so we introduce several new overdispersion estimators due to poor performance of the classic one. We used simulated data to examine estimation bias and to investigate several variance estimators with overdispersion. A real example is given of harbor seal counts from aerial surveys in an Alaskan glacial fjord. © 2014, The Author(s).
Timokhov L.,Arctic and Antarctic Research Institute |
Ashik I.,Arctic and Antarctic Research Institute |
Dmitrenko I.,Leibniz Institute of Marine Science |
Hoelemann J.,Alfred Wegener Institute for Polar and Marine Research |
And 4 more authors.
Polarforschung | Year: 2011
Large-scale features of Arctic Ocean temperature and salinity distributions observed during 2007-2009 are described and discussed in the context of historical observation in order to document long-term variations. Oceanographic observations carried out in the frame of the International Polar Year (IPY 2007/2008) demonstrated unique conditions in the Arctic Ocean and seas during that period. For example, analyses of upper ocean temperature and salinity patterns 2007-2009 revealed an apparent frontal zone separating the Eurasian and Canadian Basins. We found that after 2007 the temperature and salinity trends of the surface layer of the Arctic Ocean followed the same trajectory as in the past, however their regional distribution and intensity changed. The average salinity in the surface 5-50 m layer of the Eurasian Basin in winter of 2007-2009 was higher than in the 1950s and 1970s, but did not exceed the average salinity in the early 1990s. In the Canadian Basin, the upper ocean salinity in 2007-2009 was much lower than in the 1950s-1960s. Volumetric analysis of water masses demonstrated a general increase of volume of the intermediate (150-900 m depth range) Atlantic Water (AW) temperature, with substantial rise of the upper boundary of the AW. The thermal expansion of AW in the Arctic Basin is unique during the last 20 years. The most distinct variations of the hydrographic conditions were observed in the Canadian Basin. In general, the maximum of the AW temperature decreased in 2009 relative to 2007 and the upper boundary became shallower by 50 to 150 m the Eurasian Basin. The AW salinity in 2007-2009 was not exceptional during the IPY. Observations in the deeper layers indicated that the bottom waters have become slightly warmer and less saline.
Bhatt U.S.,University of Alaska Fairbanks |
Walker D.A.,University of Alaska Fairbanks |
Raynolds M.K.,University of Alaska Fairbanks |
Bieniek P.A.,University of Alaska Fairbanks |
And 6 more authors.
Remote Sensing | Year: 2013
Vegetation productivity trends for the Arctic tundra are updated for the 1982-2011 period and examined in the context of land surface temperatures and coastal sea ice. Understanding mechanistic links between vegetation and climate parameters contributes to model advancements that are necessary for improving climate projections. This study employs remote sensing data: Global Inventory Modeling and Mapping Studies (GIMMS) Maximum Normalized Difference Vegetation Index (MaxNDVI), Special Sensor Microwave Imager (SSM/I) sea-ice concentrations, and Advanced Very High Resolution Radiometer (AVHRR) radiometric surface temperatures. Spring sea ice is declining everywhere except in the Bering Sea, while summer open water area is increasing throughout the Arctic. Summer Warmth Index (SWI-sum of degree months above freezing) trends from 1982 to 2011 are positive around Beringia but are negative over Eurasia from the Barents to the Laptev Seas and in parts of northern Canada. Eastern North America continues to show increased summer warmth and a corresponding steady increase in MaxNDVI. Positive MaxNDVI trends from 1982 to 2011 are generally weaker compared to trends from 1982-2008. So to better understand the changing trends, break points in the time series were quantified using the Breakfit algorithm. The most notable break points identify declines in SWI since 2003 in Eurasia and 1998 in Western North America. The Time Integrated NDVI (TI-NDVI, sum of the biweekly growing season values of MaxNDVI) has declined since 2005 in Eurasia, consistent with SWI declines. Summer (June-August) sea level pressure (slp) averages from 1999-2011 were compared to those from 1982-1998 to reveal higher slp over Greenland and the western Arctic and generally lower pressure over the continental Arctic in the recent period. This suggests that the large-scale circulation is likely a key contributor to the cooler temperatures over Eurasia through increased summer cloud cover and warming in Eastern North America from more cloud-free skies. © 2013 by the authors; licensee MDPI, Basel, Switzerland.