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Proc Natl Acad Sci U S A. 2017 Oct 17;114(42):11081-11086. doi: 10.1073/pnas.1707889114. Epub 2017 Oct 2.

Early snowmelt significantly enhances boreal springtime carbon uptake.

Author information

1
Finnish Meteorological Institute, FIN-00101 Helsinki, Finland; jouni.pulliainen@fmi.fi.
2
Finnish Meteorological Institute, FIN-00101 Helsinki, Finland.
3
Department of Physics, University of Helsinki, FI-00014 Helsinki, Finland.
4
Climate Research Division, Environment and Climate Change Canada, Toronto, ON M3H 5T4, Canada.
5
Global Institute for Water Security, University of Saskatchewan, Saskatoon, SK S7N 3H5, Canada.
6
Max Planck Institute for Biogeochemistry, 07701 Jena, Germany.
7
Department of Physical Geography and Ecosystems Science, Lund University, SE-22362 Lund, Sweden.
8
Department of Forest Sciences, University of Helsinki, FI-00014 Helsinki, Finland.
9
Climate & Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94721.
10
Viikki Plant Science Centre, University of Helsinki, FI-00014 Helsinki, Finland.

Abstract

We determine the annual timing of spring recovery from space-borne microwave radiometer observations across northern hemisphere boreal evergreen forests for 1979-2014. We find a trend of advanced spring recovery of carbon uptake for this period, with a total average shift of 8.1 d (2.3 d/decade). We use this trend to estimate the corresponding changes in gross primary production (GPP) by applying in situ carbon flux observations. Micrometeorological CO2 measurements at four sites in northern Europe and North America indicate that such an advance in spring recovery would have increased the January-June GPP sum by 29 g⋅C⋅m-2 [8.4 g⋅C⋅m-2 (3.7%)/decade]. We find this sensitivity of the measured springtime GPP to the spring recovery to be in accordance with the corresponding sensitivity derived from simulations with a land ecosystem model coupled to a global circulation model. The model-predicted increase in springtime cumulative GPP was 0.035 Pg/decade [15.5 g⋅C⋅m-2 (6.8%)/decade] for Eurasian forests and 0.017 Pg/decade for forests in North America [9.8 g⋅C⋅m-2 (4.4%)/decade]. This change in the springtime sum of GPP related to the timing of spring snowmelt is quantified here for boreal evergreen forests.

KEYWORDS:

carbon uptake; earth observation; snowmelt

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