Warm spring reduced carbon cycle impact of the 2012 US summer drought.
The global terrestrial carbon sink offsets one-third of the world's fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally warm temperatures and the most severe drought since the Dust Bowl era of the 1930s, resulting in substantial economic damage. It is crucial to understand the dynamics of such events because warmer temperatures and a higher prevalence of drought are projected in a changing climate. Here, we combine an extensive network of direct ecosystem flux measurements with satellite remote sensing and atmospheric inverse modeling to quantify the impact of the warmer spring and summer drought on biosphere-atmosphere carbon and water exchange in 2012. We consistently find that earlier vegetation activity increased spring carbon uptake and compensated for the reduced uptake during the summer drought, which mitigated the impact on net annual carbon uptake. The early phenological development in the Eastern Temperate Forests played a major role for the continental-scale carbon balance in 2012. The warm spring also depleted soil water resources earlier, and thus exacerbated water limitations during summer. Our results show that the detrimental effects of severe summer drought on ecosystem carbon storage can be mitigated by warming-induced increases in spring carbon uptake. However, the results also suggest that the positive carbon cycle effect of warm spring enhances water limitations and can increase summer heating through biosphere-atmosphere feedbacks.
Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720; Department of Environmental Systems Science, ETH Zurich, 8092 Zurich, Switzerland; sewolf@ethz.ch.
Sebastian
0000-0001-7717-6993
S
Wolf
Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia;
Trevor F
TF
Keenan
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109;
Joshua B
JB
Fisher
Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720;
Dennis D
0000-0003-3496-4919
DD
Baldocchi
Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, WI 53706;
Ankur R
0000-0002-5226-6041
AR
Desai
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138;
Andrew D
AD
Richardson
US Department of Agriculture, Agricultural Research Service, Southwest Watershed Research Center, Tucson, AZ 85719;
Russell L
RL
Scott
Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331;
Beverly E
BE
Law
Department of Biology, University of New Mexico, Albuquerque, NM 87131;
Marcy E
ME
Litvak
Department of Geography, University of Kansas, Lawrence, KS 66045;
Nathaniel A
NA
Brunsell
Department of Meteorology and Air Quality, Wageningen University, 6708 PB Wageningen, The Netherlands; Centre for Isotope Research, University of Groningen, 9747 AG Groningen, The Netherlands.
Wouter
W
Peters
Department of Meteorology and Air Quality, Wageningen University, 6708 PB Wageningen, The Netherlands;
Ingrid T
0000-0002-3990-6737
IT
van der Laan-Luijkx
D002244:Carbon; D057486:Carbon Cycle; D002245:Carbon Dioxide; D055864:Droughts; D017753:Ecosystem; D045482:Hot Springs
D002245:Carbon Dioxide; D002244:Carbon
biosphere–atmosphere feedbacks; carbon uptake; ecosystem fluxes; eddy covariance; seasonal climate anomalies