Long-Term Release of Carbon
Dioxide from Arctic Tundra
Ecosystems in Alaska
E. S. Euskirchen,
* M. S. Bret-Harte,
G. R. Shaver,
C. W. Edgar,
V. E. Romanovsky
University of Alaska Fairbanks, Institute of Arctic Biology, 902 N. Koyukuk Dr., Box 757000, Fairbanks, Alaska 99775, USA
The Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA;
University of Alaska Fairbanks,
Geophysical Institute, Fairbanks, Alaska 99775, USA;
Tyumen State Oil and Gas University, Tyumen’, Russia
Releases of the greenhouse gases carbon dioxide
) and methane (CH
) from thawing permafrost
are expected to be among the largest feedbacks to
climate from arctic ecosystems. However, the current
net carbon (C) balance of terrestrial arctic ecosystems
is unknown. Recent studies suggest that these
ecosystems are sources, sinks, or approximately in
balance at present. This uncertainty arises because
there are few long-term continuous measurements of
arctic tundra CO
ﬂuxes over the full annual cycle.
Here, we describe a pattern of CO
loss based on the
longest continuous record of direct measurements of
ﬂuxes in the Alaskan Arctic, from two repre-
sentative tundra ecosystems, wet sedge and heath
tundra. We also report on a shorter time series of
continuous measurements from a third ecosystem,
tussock tundra. The amount of CO
loss from both
heath and wet sedge ecosystems was related to the
timing of freeze-up of the soil active layer in the fall.
Wet sedge tundra lost the most CO
anomalously warm autumn periods of September–
December 2013–2015, with CH
tributing little to the overall C budget. Losses of C
translated to approximately 4.1 and 1.4% of the total
soil C stocks in active layer of the wet sedge and heath
tundra, respectively, from 2008 to 2015. Increases in
air temperature and soil temperatures at all depths
may trigger a new trajectory of CO
will be a signiﬁcant feedback to further warming if it is
representative of larger areas of the Arctic.
Key words: arctic tundra; net ecosystem
exchange; permafrost; soil temperature;
carbon dioxide; methane.
In the Arctic, the rate of climate change is now
faster than natural ecosystem adaptation (Duarte
and others 2012). Mean annual air temperature is
currently 1.5°C higher than the 1971–2000 mean,
with the greatest increases having occurred in the
autumn and winter (Jeffries and others 2013). This
warming in the Arctic is more than double the
warming at lower latitudes (Overland and others
2013). In a changing arctic climate, one of the most
signiﬁcant potential feedbacks from terrestrial
Received 16 May 2016; accepted 13 September 2016;
published online 21 November 2016
Electronic supplementary material: The online version of this article
(doi:10.1007/s10021-016-0085-9) contains supplementary material,
which is available to authorized users.
Author Contributions E.S.E, M.S.B.H., and G.R.S. conceived the
micrometeorological study and scientiﬁc objectives. V.E.R. designed and
installed the borehole temperature measurements and analyzed the data.
E.S.E. and C.W.E. processed and analyzed the micrometeorological data.
M.S.B.H. and C.W.E. collected, processed, and analyzed the soil C data.
All authors commented on the analysis and presentation of the data.
E.S.E wrote the paper with contributions from all authors.
Data for our project can be found on our project webpage at: http://aon.
*Corresponding author; e-mail: email@example.com
Ecosystems (2017) 20: 960–974
Ó 2016 Springer Science+Business Media New York