Coupled Biogeochemical Cycles:
A Perspective on Earth System Science
for the LAND Open Science Conference,
Morelia, Mexico
December 1-5
Elisabeth Holland
with
Gordon Bonan, Scott Doney, Inez
Fung, Alex Guenther, Natalie
Mahowald. David Schimel, Britton
Stephens. Jielun Sun, Peter
Thornton
and Louisa Emmons, Peter Hess,
Jean-Francois Lamarque
And others
Climate Forcing
The contemporary carbon cycle
Carbon/Climate Control
Simulation (~100y)
+1.0
14.1
-1.0
Net CO2 Flux
13.7
284
Surface Temp.
“Stable” carbon cycle and
climate over O(100y) with fully
prognostic land/ocn BGC and
carbon/radiation coupling
Fung, Doney and John
283
282
Surface Atm. CO2
Time-evolving, 3-D
Atmospheric CO2
fields
Fung, Doney and John
Putting the pieces together:
The GLOBAL C CYCLE
The GLOBAL N CYCLE
is the N cycle
What isHow
the acceleration
of the changing?
N cycle?
Based on Nevison and Holland 1998
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
How has the quantity and pattern of N deposition changed over the last 100
years?
IPCC (2001) notes geographic shift in NOx emissions for SRES scenarios
?
What is future pattern of N
deposition likely to be?
What is the possibility that coupled
biogeochemical cycles driven by
humans represent key non-linearities
or thresholds in the Earth system?
What are the implications of N deposition
for the global carbon cycle with a simple perturbation approach?
from Holland et al 1997, JGR Atmospheres 102:15,849-15,866).
New Land BGC model
-Nitrogen/Carbon Coupling
-Disturbance
NEE response to +1° C step change (decid broadleaf)
N-limited
non N-limited
Thornton et al.
What is N saturation?
Aber et al. 1989, Bioscience
What happens when N deposition increases 10X?
To N retention ?
To carbon storage?
Do these simulations provide any evidence of N
saturation characterized by a non-linear increase in
outputs relative to inputs?
Coniferous Forests current N deposition
N losses
4.71
Deciduous Forests Current N deposition
5.21
10X
10X
Mixed Forests
Shrublands
Savannas
Grasslands
Current N deposition
10X
Current N deposition
10X
Current N deposition
10X
Current N deposition
10X
29.78
32.14
4.80
30.82
1.50
10.75
8.78
55.94
5.77
39.14
N losses=gaseous losses (NO + NH3 +N2O+ nitrate leaching, kg N ha-1 y-1
Holland, Braswell and Bossdorf, in prep.
NO!
IPCC SRES Scenarios for the TAR
Past, Present and Future
Tropospheric O3 Abundance
• Pre-industrial O3 (1750) : 25 Dobson Units (DU) with
background surface concentrations of ~8-15 ppb
• Current O3: increase of 9 DU with a range of 6-13 DU
• O3 in 2100: increase of 3-21 DU with background N hemisphere
concentrations of 80 ppb during the summer.
from the IPCC TAR, Chapter 4, Prather, Ehhalt et
al.2001, 1 DU= 10.9 Tg O3 and 1 ppb O3 = 0.63 DU.
What does the future hold ?
Compound
Greenhouse gases
CO2-fossil fuel
CH4
N2O
O3 precursors
C: NMVOCs + CO
N: NOx
Sulfate aerosol
precursors
SO2
Average
Range
+167%
+62
+44
(-28 to +405)
(-24 to 137)
(-19 to 148)
+85%
+98%
(-59 to 202)
(-39 to 192)
-48
(-15 to Ğ72)
IPCC SRES scenario emissions: % increases
projected for 2100, relative to 2000
N forcing
Summary for Policymakers, IPCC 2001
Humans are driving the nitrogen cycle and it has
important implications for our health!
air & water
pollution,
ecological
feedbacks
to disease
Effects on
Public Health
crop yields,
nutrition,
infrastructure
Net Public
Health Benefit
Human N Fixation and Use
IPCC Meeting on Current Scientific
Understanding of the Processes Affecting
Terrestrial Carbon Stocks and Human Influences
upon Them
Geneva, Switzerland, July, 2003
•
The coupling of nitrogen deposition to the carbon cycle is not yet fully
understood (including the process of nitrogen saturation) and
consequently it is not adequately represented or even included in
current models. The non-linearity of nitrogen responses needs to be
included in both models and experimental procedures, and interactions
between nitrogen effects and pollutant feedbacks on carbon uptake
may be of growing importance. These interactions and their nonlinearities are not adequately considered in current measurement and
modeling studies. Studies of the combined effect of air quality,
nitrogen, elevated CO2 and carbon cycling are needed before we can
answer the interrelated questions of separability, attribution and
stability in the growing number of regions affected by changing
atmospheric chemistry.
WMO
INTERGOVERNMENTAL PANEL ON CLIMATE
CHANGE
TWENTY-FIRST SESSION
Vienna, 3 and 6-7 November 2003
UNEP
CHAPTER OUTLINE OF THE WORKING GROUP I CONTRIBUTION
TO THE IPCC FOURTH ASSESSMENT REPORT (AR4)
7. Couplings Between Changes in the Climate System and Biogeochemistry
Executive Summary
· Introduction to Biogeochemical Cycles
· The Carbon Cycle and the Climate System
· Global Atmospheric Chemistry and Climate Change
· Air Quality and Climate Change
· Aerosols and Climate Change
· The Changing Land Surface and Climate
· Synthesis: Interactions Among Cycles and Processes
The NCAR Biogeosciences
Initiative:
Transferring knowledge from local to global scales through integrated observation
and modeling of physical and biological processes
Elisabeth Holland (Program Leader), Gordon Bonan, Alex Guenther, Natalie Mahowald,
David Schimel, Britton Stephens, Jielun Sun, and Peter Thornton (Steering Committee)
Steve Aulenback, David Baker, Teresa Campos, Tony Delaney, Scott Doney, Alan Fried,
Don Lenschow, Keith Lindsay, Kimberly Mace, Cindy Nevison, Steve Oncley, Dirk Richter, Nan
Rosenbloom,
and Steve Shertz
How does N saturation affect the C sink?
Comparison of Terrestrial Net CO 2 Flux Estimated by Inverse Deconvolution
and Our Perturbation Estimate of Terrestrial Net CO 2 Flux from N Deposition .
Units are Gt C yr -1.
90°S–16
Equatorial 16°N–90°
Global
°S
N
-0.1
+0.3
-0.6
-0.5
Keeling et al . [1989] a
Tans et al . [1994] a
Ciais et al . [1995] b
This work
MOGUNTIA NOy only c
MOGUNTIA NHx + NO yd
This work
MOGUNTIA NOy only c
MOGUNTIA NHx + NO y d
-0.1
-0.2
+0.5
+0.8
-2.3
-2.2
-1.9
-1.5
-0.40
-0.73
-0.61
-1.09
-0.64
-1.02
-0.90
-1.42
With N Saturation
-0.05
-0.10
-0.16
-0.26
Without N Saturation
-0.06
-0.11
-0.20
-0.29
a
Based on CO2 concentrations, bBased on 13CO2 + CO2.
Includes NOy deposition from fossil fuel combustion and 50% of nonfossil fuel NOy.
d
Includes NOy deposition from fossil fuel combustion and 50% of nonfossil fuel NOy plus 50% of NHx deposition.
c
from Holland et al 1997, JGR Atmospheres 102:15,849-15,866).
How does increased N deposition influence the
internal N dynamics of the system?
How does N retention vary with N
deposition?
Holland, Braswell and Bossdorf
How does N deposition
impact C storage across a
range of vegetation types?
What is the right answer?
• Estimated continental C sink for the US:
– Perturbation calculation, conservative FF NOx + 50% NOx +
NHx budget: 0.14 Pg C
– Full up climate + C, N feedbacks +(modern - background N
deposition) : 0.0.14 Pg C
Where are the measurements made in the US?
Wet deposition of NH4+
Dry deposition of particulate NH4+
Wet deposition of NO3-
Dry deposition of HNO3 (g)
Dry deposition of particulate NO3-
All units kg N ha-1 y-1
Holland, Braswell, Sulzman, Lamarque submitted
What data is available in Europe?
How does total N deposition in US compare with Europe?
Do N emissions balance N deposition?
For the contiguous US?
NOx
Estimated emissions1
6.24–6.35
Integrated deposition
NOy
Wet deposition fluxes
∑ Dry deposition fluxes
∑ wet + dry
Imbalance
All units are Tg N
1.28
NH3
NOx + NH3
3.6-5.2
9.84–11.55
NHx
NOy + NHx
1.08
2.36
1.20
0.18-0.98
1.38-2.18
2.48
1.26-2.06
3.74-4.54
3.76 to 3.87
1.54 to 3.94
5.30 to 7.81
Do N emissions balance N deposition?
For Western Europe?
NOx
Estimated emissions1
Integrated deposition
Wet deposition fluxes
6.1
NOy
2.34
NH3
4.1-5.2
NHx
3.96
NOx + NH3
10.2Ğ11.2
NOy + NHx
6.30
Dry deposition fluxes
HNO3 + particulate NO3-
0.55-2.27
0.55-2.27
NO2
1.24
1.24
particulate NH4+7
∑ Dry deposition fluxes
∑ wet + dry
Imbalance
All units are Tg N
0.33-1.34
0.33-1.34
1.75Ğ3.52
0.33-1.01
2.08-4.53
4.13-5.85
4.29-6.31
8.42-10.83
1.97 to 0.25
-1.11 to 0.91
-0.63 to 2.88
1c. Species Responses
How does a changing N cycle set the rules
for other critical changes to the environment?
• Invasives
• Overall Diversity
Control
N Fertilized