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Uma S. Bhatt
,
Donald A. Walker
,
Martha K. Raynolds
,
Josefino C. Comiso
,
Howard E. Epstein
,
Gensuo Jia
,
Rudiger Gens
,
Jorge E. Pinzon
,
Compton J. Tucker
,
Craig E. Tweedie
, and
Patrick J. Webber

the decline in sea ice is linked to increases in land temperatures and tundra productivity. We use a newly available satellite-derived dataset of Arctic Normalized Difference Vegetation Index (NDVI; J. E. Pinzon et al. 2010, unpublished manuscript) to demonstrate a consistent temporal relationship between sea ice, NDVI, and land temperatures over Arctic tundra. These data permitted the first circumpolar analysis over tundra of NDVI changes in the High Arctic north of 72°N. The spatial patterns

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Gunter Weller
and
Bjorn Holmgren

854 JOURNAL OF APPLIED METEOROLOGY Vo~.~mml$The MicrocllmRtes of the Arctic Tundra GUNTER WELLER AND BJoalq HOLMGRENGeophysical Instilul~, Uni~-rsily of A tas~a, Fairbanks 00701(Manuscript receiYed 13 November 1973, in revised form 24 July 1974) ABSTRACT The microclimates of the arctic tundra at Barrow, Alaska, are described/or the near-surface terrestria~layers Ln

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Matthew Sturm
,
Jon Holmgren
,
Joseph P. McFadden
,
Glen E. Liston
,
F. Stuart Chapin III
, and
Charles H. Racine

tundra to climate change. 2. Study design We measured variations in snow properties and vegetation across a landscape in arctic Alaska (69°06′N, 149°00′W) covered by three types of vegetation: 1) tussock tundra, 2) shrubby tussock tundra, and 3) riparian shrub ( McFadden et al. 1998 ). The site was near Happy Valley on the Dalton Highway, about half-way between Prudhoe Bay and the Brooks Range. Several shallow water tracks drained the gently sloping area. These were oriented perpendicular to the

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Sebastian A. Krogh
and
John W. Pomeroy

studies investigating changes in the forest structure (i.e., density, height, and extension) over northwestern Canada. Payette and Filion (1985) found that white spruce tree lines in northern Quebec have not substantially changes over the past centuries, whereas Suarez et al. (1999) found that the tundra–taiga tree line in Alaska advanced northward between 80 and 100 m north over the last 200 years. Gamache and Payette (2004) studied black spruce height near the Arctic tree line in eastern

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Gerald V. Frost
,
Uma S. Bhatt
,
Matthew J. Macander
,
Amy S. Hendricks
, and
M. Torre Jorgenson

. 2019 ), changing tundra productivity ( Bhatt et al. 2010 ; Bieniek et al. 2015 ), tundra shrub expansion ( Myers-Smith et al. 2011 ), and increased coastal flooding and erosion ( Vermaire et al. 2013 ). These processes have already driven changes to the abundance and management of marine and terrestrial resources [e.g., fisheries and moose ( Alces alces )] ( Mueter and Litzow 2008 ; Perry 2010 ), and even prompted the relocation of villages (e.g., Newtok). Yet, current understanding of Arctic

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A. H. Lynch
,
F. S. Chapin III
,
L. D. Hinzman
,
W. Wu
,
E. Lilly
,
G. Vourlitis
, and
E. Kim

1. Introduction and historical perspective Although the surface energy balance is of fundamental importance to meteorological, hydrological, geomorphological, and ecological processes, the controls over the surface energy balance and its relationship to climate have not been well characterized for arctic and alpine tundra ecosystems. Greater attention has been paid to tropical environments (e.g., Henderson-Sellers and Gornitz 1984 ; Nobre et al. 1991 ) and boreal forest, particularly the

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J. S. Kimball
,
M. Zhao
,
A. D. McGuire
,
F. A. Heinsch
,
J. Clein
,
M. Calef
,
W. M. Jolly
,
S. Kang
,
S. E. Euskirchen
,
K. C. McDonald
, and
S. W. Running

1. Introduction Boreal forest and arctic tundra biomes of the northern high latitudes (>40°N) are currently undergoing significant changes coinciding with recent and persistent climatic warming ( Serreze et al. 2000 ; Comiso 2003 ). Terrestrial ecosystem responses to the warming trend include thawing permafrost and deepening soil active layer depths ( Oelke et al. 2004 ), advances in the timing and length of seasonal growing seasons ( Myneni et al. 1997a ; McDonald et al. 2004 ), changes in

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Richard Essery
and
John Pomeroy

of snow water resources and hazards, but snow depth and mass distributions also have important influences on climate and ecology. Snow redistributed to shrubs in the low Arctic contains high chemical loads of essential plant nutrients such as inorganic nitrogen, and shrubs have deeper snow than adjacent sparsely vegetated tundra ( Pomeroy et al. 1995 ). Snow cover provides a direct physical protection to plant stems from abrasion by blowing-snow grains, and deeper snowpacks reduce overwinter soil

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Maxim Lamare
,
Florent Domine
,
Jesús Revuelto
,
Maude Pelletier
,
Laurent Arnaud
, and
Ghislain Picard

1. Introduction In northern regions, the snow cover insulates the ground from the winter cold air and therefore plays a key role in the permafrost thermal regime ( Zhang 2005 ). With global warming, shrubs are expanding on Arctic tundra ( Ju and Masek 2016 ; Tremblay et al. 2012 ) and this has been observed to lead to increases in snow height in some cases ( Busseau et al. 2017 ; Sturm et al. 2001 ). Here, we use the term “snow height” rather than the more common “snow depth” because we

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Amy S. Hendricks
,
Uma S. Bhatt
,
Gerald V. Frost
,
Donald A. Walker
,
Peter A. Bieniek
,
Martha K. Raynolds
,
Rick T. Lader
,
Howard E. Epstein
,
Jorge E. Pinzon
,
Compton J. Tucker
, and
Josefino C. Comiso

1. Introduction A defining feature of Arctic climate change is the striking response of tundra vegetation productivity to increasing summer temperatures, a phenomenon known as the “greening of the Arctic” ( Myneni et al. 1997 ; Jia et al. 2003 ). Remotely sensed trends of vegetation productivity are derived from satellite sensors such as the Advanced Very High Resolution Radiometer (AVHRR); red and near-infrared reflectance are used to calculate the normalized difference vegetation index

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