[1] This synthesis addresses the vulnerability of the North American high‐latitude soil organic carbon (SOC) pool to climate change Disturbances caused by climate warming in arctic, subarctic, and boreal environments can result in significant redistribution of C among major reservoirs with potential global impacts We divide the current northern high‐latitude SOC pools into (1) near‐surface soils where SOC is affected by seasonal freeze‐thaw processes and changes in moisture status, and (2) deeper permafrost and peatland strata down to several tens of meters depth where SOC is usually not affected by short‐term changes We address key factors (permafrost, vegetation, hydrology, paleoenvironmental history) and processes (C input, storage, decomposition, and output) responsible for the formation of the large high‐latitude SOC pool in North America and highlight how climate‐related disturbances could alter this pool’s character and size Press disturbances of relatively slow but persistent nature such as top‐down thawing of permafrost, and changes in hydrology, microbiological communities, pedological processes, and vegetation types, as well as pulse disturbances of relatively rapid and local nature such as wildfires and thermokarst, could substantially impact SOC stocks Ongoing climate warming in the North American high‐latitude region could result in crossing environmental thresholds, thereby accelerating press disturbances and increasingly triggering pulse disturbances and eventually affecting the C source/sink net character of northern high‐latitude soils Finally, we assess postdisturbance feedbacks, models, and predictions for the northern high‐latitude SOC pool, and discuss data and research gaps to be addressed by future research

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Vulnerability of high-latitude soil organic carbon in North America to disturbance

As the Arctic warms, vegetation is responding, and satellite measures indicate widespread greening at high latitudes. This ‘greening of the Arctic’ is among the world’s most important large-scale ecological responses to global climate change. However, a consensus is emerging that the underlying causes and future dynamics of so-called Arctic greening and browning trends are more complex, variable and inherently scale-dependent than previously thought. Here we summarize the complexities of observing and interpreting high-latitude greening to identify priorities for future research. Incorporating satellite and proximal remote sensing with in-situ data, while accounting for uncertainties and scale issues, will advance the study of past, present and future Arctic vegetation change.

/pdf/complexity-revealed-in-the-greening-of-the-arctic-53zvzgjrxk.pdf

Complexity revealed in the greening of the Arctic

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(09)61716-5.pdf

Public health benefits of strategies to reduce greenhouse-gas emissions: health implications of short-lived greenhouse pollutants.

Linkages between diminishing Arctic sea ice and changes in Arctic terrestrial ecosystems have not been previously demonstrated. Here, the authors use a newly available Arctic Normalized Difference Vegetation Index (NDVI) dataset (a measure of vegetation photosynthetic capacity) to document coherent temporal relationships between near-coastal sea ice, summer tundra land surface temperatures, and vegetation productivity. The authors find that, during the period of satellite observations (1982–2008), sea ice within 50 km of the coast during the period of early summer ice breakup declined an average of 25% for the Arctic as a whole, with much larger changes in the East Siberian Sea to Chukchi Sea sectors (>44% decline). The changes in sea ice conditions are most directly relevant and have the strongest effect on the villages and ecosystems immediately adjacent to the coast, but the terrestrial effects of sea ice changes also extend far inland. Low-elevation (<300 m) tundra summer land temperatures, a...

/pdf/circumpolar-arctic-tundra-vegetation-change-is-linked-to-sea-3u95j13i5c.pdf

Circumpolar Arctic Tundra Vegetation Change Is Linked to Sea Ice Decline

The vegetation greenness trend in Canada and US Alaska from 1984–2012 Landsat data

Arctic landscapes have visually striking patterns of small polygons, circles, and hummocks. The linkages between the geophysical and biological components of these systems and their responses to climate changes are not well understood. The "Biocomplexity of Patterned Ground Ecosystems" project examined patterned-ground features (PGFs) in all five Arctic bioclimate subzones along an 1800-km trans-Arctic temperature gradient in northern Alaska and northwestern Canada. This paper provides an overview of the transect to illustrate the trends in climate, PGFs, vegetation, n-factors, soils, active-layer depth, and frost heave along the climate gradient. We emphasize the thermal effects of the vegetation and snow on the heat and water fluxes within patterned-ground systems. Four new modeling approaches build on the theme that vegetation controls microscale soil temperature differences between the centers and margins of the PGFs, and these in turn drive the movement of water, affect the formation of aggradation ice, promote differential soil heave, and regulate a host of system propel-ties that affect the ability of plants to colonize the centers of these features. We conclude with an examination of the possible effects of a climate wan-ning on patterned-ground ecosystems.

/pdf/arctic-patterned-ground-ecosystems-a-synthesis-of-field-1g55tr9x5r.pdf

Arctic patterned-ground ecosystems: A synthesis of field studies and models along a North American Arctic Transect

NDVI (Normalized Difference Vegetation Index) calculated from coarse-resolution sensors has shown strong increases since the 1980s on Alaska's North Slope. Finer-resolution satellite data and ground studies are needed to understand the changes in the vegetation that are causing these increases. Analysis of an 823 km2 area using a Landsat NDVI time series showed that the homogeneous greening at coarser scales was very heterogeneous at 30-m pixel resolution, with a strong influence due to glacial history. Small scattered patches of pixels with significant increases in NDVI occurred throughout the younger, late Pleistocene glacial deposits. On older, mid-Pleistocene deposits, increases occurred in few, larger patches of mostly tussock-sedge, dwarf-shrub, moss tundra, possibly a result of release of nutrients from thawing of ice-rich permafrost. Five percent of pixels had significant linear increases in NDVI from 1985 to 2007 (n = 6, p < 0.05), while 0.4% showed significant decreases, in small patche...

https://www.tandfonline.com/doi/pdf/10.1657/1938-4246-45.2.249

Patterns of Change within a Tundra Landscape: 22-year Landsat NDVI Trends in an Area of the Northern Foothills of the Brooks Range, Alaska

[1] Arctic patterned-ground features have been described individually, but never examined as parts of integrated landscape/ecosystems that vary along the Arctic climate gradient. Here we examine the complex interrelationships between patterned ground, climate, vegetation and soil along a north-south transect through all five bioclimate subzones of the North American Arctic. We mapped the vegetation, biomass, end-of-summer thaw depths, and snow cover on twenty 10 × 10-m grids. The vegetation maps illustrate the transition of vegetation types and patterns from north to south. Biomass maps showed lower biomass in the centers of patterned-ground features than in areas between features, and increasing biomass from north to south. Thaw-depth maps showed deeper thaw in the centers of features than between features, and shallow thaw on the north and south ends of the transect. Snow depth maps showed less snow on patterned-ground features subject to differential frost heave compared to areas between features which did not heave, and a north-south gradient of increasing snow depth. The maps also documented the change from small nonsorted polygons to larger nonsorted circles from north to south, and increasing pattern size with moisture. Principal components analysis revealed underlying relationships between patterned-ground landscapes and measured vegetation and environmental variables. Climate in combination with the vegetation was the most important factor affecting patterned ground on zonal sites, but soil moisture, texture and chemistry were also important.

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Corinne A. Munger

Papers

Arctic patterned-ground ecosystems: A synthesis of field studies and models along a North American Arctic Transect

Patterns of Change within a Tundra Landscape: 22-year Landsat NDVI Trends in an Area of the Northern Foothills of the Brooks Range, Alaska

A map analysis of patterned‐ground along a North American Arctic Transect

Glacial History and Long-Term Ecology in the Toolik Lake Region

A map analysis of patterned-ground along a North American