Transcript Biogeochemical Surprises In a Changing Climate Ankur R Desai Dept. Atmospheric & Oceanic Sciences Ankur of Desai, Atmospheric & Oceanic Sci., UW-Madison University Wisconsin-Madison CEE 698: Sustainabilityof Principles, Practices, and Paradoxes Feb 9, 201010 March 2010 UMN SWC.

Biogeochemical Surprises
In a Changing Climate
Ankur R Desai
Dept.
Atmospheric
& Oceanic
Sciences
Ankur of
Desai,
Atmospheric & Oceanic
Sci., UW-Madison
University
Wisconsin-Madison
CEE 698:
Sustainabilityof
Principles,
Practices, and Paradoxes
Feb 9, 201010 March 2010
UMN SWC Seminar,
Biogeo-what?
• Land and ocean ecosystems have
biophysical and biogeochemical
dependences on the atmosphere
– Biophysical – Interactions of moisture, heat,
solar radiation between ecosystems and
atmosphere
– Biogeochemical – Cycling of nutrients,
especially carbon and nitrogen
• As the atmosphere changes, both of these
are changing in ecosystems! Leading to:
SURPRISE!
SURPRISE!
• Ecosystems are generally evolutionarily
adapted to regional climate and its shortterm variability
• Expectations of how these ecosystems
respond to climate variation are the
bedrock of ecosystem ecology
• But: Surprises are likely given the complex
interplay between ecosystems and climate
SURPRISE!
Gutschick and BassiriRad (2010)
SURPRISE!
• Surprises are no fun for ecosystem
management
• But: It’s also how science progresses
• And: We are likely entering an era where
surprises will be more common.
Why?
Our Era
• From 1990-2005:
– World Population increased 22% to
~6,500,000,000 people
– Global oil consumption grew 25% to
85,000,000 barrels per day
– Gross World Product (GWP) grew 40% to
$59,380,000,000,000 US dollars
– The number of threatened species increased 40% to
~16,000
• Population doubling times have increased
– 1850-1930, 80 years, 1-2 billion
– 1930-1975, 45 years, 2-4 billion
– 1975-2015, 40 years, 4-8 billion
Source: UCAR
Why? CO2!
Global monthly average CO2 in parts per million (ppm)
Source: NOAA ESRL
A Global Experiment
CO2 (ppm)
385 ppm
(2008)
232 ppm
Ice ages
Years Before Present
Source: Lüthi et al (2008), CDIAC, & Wikimedia Commons
Our Carbon Economy
Global Energy Production 1850 to 1994
450
400
350
Nuclear
Hydro
Exajoules per Year
300
Gas
Oil (feedstock)
250
Oil
Coal
200
Wood
CARBON!
150
100
50
94
19
88
82
19
19
76
19
70
64
19
19
58
52
19
46
19
19
40
34
19
19
28
19
22
16
19
19
10
19
04
98
19
18
92
18
86
18
80
74
Source: IEA
18
18
68
62
18
56
18
18
18
50
0
Since 1990
• Global annual CO2 emissions grew 25% to
27,000,000,000 tons of CO2
• CO2 in the atmosphere grew 10% to
385 ppm
• At current rates, CO2 is likely to exceed
500 ppm sometime this century
• But: Rate of atmospheric CO2 increase is about
half the rate of emissions increase. Why?
Where Is The Carbon Going?
Houghton et al. (2007)
Carbon Cycle
Houghton et al. (2007)
What’s The Big Deal?
IPCC, 4th AR, (2007)
Living in a Greenhouse
Infrared
Solar
Weather
Land/Ocean
Trenberth et al. (2009)
The Big Deal
IPCC AR4 (2007)
The Big Deal
IPCC AR4 (2007)
A Small Problem
Friedlingstein et al. (2005)
No Surprises Here
• The better we can reduce uncertainty of
how ecosystem carbon cycles respond to
climate, the better we can model future
climate change and impacts
• I will present two examples to illustrate
surprises of ecosystem responses to a
changing climate based on research
conducted by my lab and collaborators
• And then some thoughts on what’s next…
Story #1
• Expectation:
– Warmer Spring leads to a longer growing
season for plants in high-elevation forests
• Therefore:
– Forest productivity in the Rocky Mountains
should benefit from global warming
That Makes Some Sense
Later springs lead to lower productivity in U.S. northeastern forests
Onset of Spring Anomaly (Days)
• Richardson et al. (2009)
It’s Getting Warmer Out There
• April max monthly temperature trend 1971-2000
Courtesy of R. Behnke, UW; Data source: PRISM group
It’s Getting Warmer Out There
In spring, higher elevations are warming faster than lower
Courtesy of R. Behnke, UW
Hmmm….
• Niwot Ridge Ameriflux subalpine fir/spruce
– 3050m elevation
Hu et al. (2010)
SURPRISE!
A Tower To Rule Them All
A Flux Tower
• NEE = Net Ecosystem Production
– Positive = More productivity
Courtesy of R. Monson, CU-Boulder
Moisture Matters
Hu et al. (2010)
More Evidence
Soil sfc
Rain
Soil 35 cm
Groundwater
Snowmelt
WATER
SNOW
Hu et al. (2010)
Snow Moisture Matters
• Snow water drives a lot of productivity in
Rocky Mountain subalpine forests
Water
Snow
Hu et al. (2010)
Water
Snow
Water
Snow
Is It Regional?
• ACME07
UPWIND
DOWNWIND
Ahue et al. (in prep)
Is It Regional?
Niwot Ridge
CarbonTracker
Airborne budget
Ahue et al. (in prep)
Moral for Story #1
• Warming temperatures are not necessarily
a net positive for ecosystem productivity
• Changes in moisture levels and snow
matter in Western Forests
Montaine subalpine forests
Don’t Forget Bugs!
Raffa et al. (2008)
Pine Beetles
Raffa et al (2008)
Another Warming Feedback
Courtesy of B. Stephens, NCAR
Another Warming Feedback
Mostly alive
Mostly dead
• Declining trend in atmospheric valley CO2?
Courtesy of B. Stephens, NCAR
Rate of Spread
Beetle-Climate Feedback
Spruce beetle
Mountain Pine Beetle
Raffa et al (2008)
Bugs and Forest Carbon
Amiro et al (in prep); Hicke et al (in prep)
Story #2
• Expectation:
– Wet places like temperate regions are not
sensitive to variations in precipitation
• Therefore:
– North temperate wetland productivity
shouldn’t vary with groundwater elevation
Some Wet Places
Sulman et al. (in prep)
What Drives Hydrology?
• Water table elevation is driven by
precipitation and evaporation
Sulman et al. (2009)
Lakes Levels Are Dropping
Stow et al. (2008)
Methods
• Flux tower Net Ecosystem Exchange (NEE) is
observed, QC-ed, filtered, gap-filled
• Fluxes of photosynthesis (gross primary
production – GPP) and ecosystem respiration (ER)
derived from moving window regression of NEE
to environmental variables
• Results compared to water table depth
observations
• Six state of the art ecosystem models
parameterized and run at 3 sites with same
meteorological forcing and biometric info.
Some Models
Monthly NEE 2000-2006 (μmol m-2 s-1)
5
Lost Creek Shrub Fen
0
?
-5
-70
Courtesy of N. Shroeder, UW
20
Water Table Height (cm)
What’s Up With Fens?
• GPP = Gross Primary Productivity
Sulman et al. (2009; in prep)
Do Models Get This?
Monthly GPP 2000-2006 (μmol m-2 s-1)
14
Lost Creek Shrub Fen
6
0
-70
Courtesy of N. Shroeder, UW
20
Water Table Height (cm)
SURPRISE!
Respiration Puzzle
Sulman et al. (in prep)
Anomalies Are More Striking
Sulman et al. (in prep)
What’s Driving This?
Sulman et al. (in prep)
What’s Driving This?
• Adaptation of plants to drying conditions
leads to increases in water use efficiency,
especially for fens, maybe?
Sulman et al. (in prep)
Moral for Story #2
• Ecosystems in wet regions are not immune
to shifts in precipitation/hydrologic regimes
• Plants adapt to change, but the timescale
depends on the kind of ecosystem
Mesic forests?
Temperate fens
And Of The Region?
• Northern Wisconsin is a mix of upland
forest (70%) and wetland (30%)
– Should fluxes respond to precipitation or water
table?
• We can estimate regional fluxes using topdown inverse or boundary layer budget
approaches or bottom-up from forest
inventory or flux-tower optimized
ecosystem modeling.
Methods
• Bottom-up (scaling)
– IFUSE – Interannual Flux-Tower Upscaling Experiment
• 12 regional flux towers categorized by land cover and age are used
to parameterize simple regional model using MCMC approach (Desai
et al., 2008; in prep)
– ED – Ecosystem Demography Model 1.5
• Height-and-age cohort succession model tuned to Forest Inventory
and Analysis (FIA) data (Desai et al., 2007)
• Top-down (atmospheric budgets)
– EBL – Equilibrium Boundary Layer
• 1-D boundary layer budget inferred from WLEF 447-m tall tower CO2
profile, NOAA marine CO2 flask network, and NARR reanalysis
subsidence rates (Helliker et al, 2004)
– CT – CarbonTracker
• Global, nested-grid inverse model based on CASA surface model,
global surface continuous and flask CO2 network, and Ensemble
Kalman Filter tracer-transport assimilation with TM5 winds (Peters et
al., 2007)
Regional Flux
• Magnitudes vary, but variability is similar
Desai et al (in press)
Regional and Water
• Prior year water table strong influences
anomalies in regional NEE
Desai et al (in press)
The Last Surprise!
Morals: Nothing Is Simple
• Rising temperature can have beneficial and
deleterious effects on ecosystems
– Depends on the season
– Seasonal lags are likely (i.e., can’t neglect
winter in temperate systems)
• Moisture stress covaries with precipitation
and temperature
• There are many kinds of stressors on an
ecosystem – the interactions of these is
where we find the most surprises
Atm. Chem, O3
Precipitation
Temperature
Aerosols
GHGs
NOx
Heat
CO2
Ecosystems
H2O
VOCs
Conclusions
• Carbon and water cycling linkages require close
examination in ecosystem models
– Don’t treat all ecosystems with the same paintbrush
• Complex interactions between the physical environment
and all biological systems (e.g., insects, microbes) should
not be underestimated
– Models that incorporate, test, and verify these interactions can
help us anticipate surprises
• Slow, steady rates of change allow us to anticipate and
react to surprises; rapid climate surprises are likely to
exacerbate ecosystem surprises
– Policies that slow climate change or destabilization are wise with
respect to minimizing ecosystem disruption
Acknowledgements
• Desai Ecometeorology Lab (flux.aos.wisc.edu):
• Funding partners: UW Graduate school, NSF,
UCAR, NOAA, USDA, NASA, DOE
• Many, many collaborators…
Acknowledgements
•
Story 1:
–
–
–
–
–
–
•
UW: Will Ahue*, Ruben Behnke*, Bjorn Brooks*
CU-Boulder: Russ Monson, Jia Hu
King’s College: Dave Moore
NCAR: Britt Stephens, Teresa Campos, Steve Aulenbach
NEON: Dave Schimel
Harvard: Andrew Richardson
Story 2:
–
–
–
–
–
–
–
–
–
–
UW: Ben Sulman*, Nicole Schroeder*, Jonathan Thom*
SUNY-Buffalo: D. Scott Mackay
USFS: Nic Saliendra, Ron Teclaw, Dan Baumann
NASA: Bruce Cook; NOAA: Arlyn Andrews
UMN: Paul Bolstad
U. Lethridge: Larry Flanagan; Trent U.: Peter Lafleur
UC-Berkeley: Oliver Sonnentag
Environment Canada: Alan Barr
U. Penn: Brent Helliker
Harvard: Paul Moorcroft
Extra Slides
Reading us another story, daddy,
pleeeee-ase?!?
Story #3
• Expectation:
– Climate change warms air faster than water
• Therefore:
– Large lake ecosystems are buffered from the
impacts of global warming
Big Lakes
Lake Superior Temperature Trends
Land
Water
Water-Land
Desai et al. (2009)
SURPRISE!
A Year In The Life Of A Buoy
Courtesy of J. Austin, UM-Duluth
Ice-Albedo Feedback
• Warmer winters = Less Ice =
More Heat Input = Warmer summers
Courtesy of J. Austin, UM-Duluth; J. Magnuson, UW
Ecosystem Impact
Current speed
Stratified Season Length
Mixed layer depth
Desai et al. (2009)
Ecosystem Impact
• We’ve begun to develop and run a 3-D
model of lake circulation and productivity
• Impacts: to be determined…
1998
1997
Courtesy of G. McKinley & V. Bennington
Lake Effect
• Simple enough…
But Wait, It Get’s Weirder
Desai et al. (2009)
An Atmospheric Feedback
Desai et al. (2009)
Moral for Story #3
• Large lake heat budgets are sensitive to
dynamics of ice
• Lake heat budgets drive lake stratification
and consequently lake productivity
• Circulation impacts are puzzling
Lakes with ice