Transcript Warming may release methane from large Arctic reservoirs

Review of Methane Mitigation Technologies with Application to Rapid Release of Methane from the Arctic
Joshuah K. Stolaroff, Subarna Bhattacharyya, Clara A. Smith, William L. Bourcier, Philip J. Cameron-Smith, and Roger D. Aines
Lawrence Livermore National Laboratory, Livermore, California, United States
dx.doi.org/10.1021/es204686w | Environ. Sci. Technol. 2012, 46, 6455−6469
ABSTRACT: Methane is the most important greenhouse gas after carbon dioxide, with particular influence on near-term climate change.
It poses increasing risk in the future from both direct anthropogenic sources and potential rapid release from the Arctic. Significant gaps in understanding
remain of the mechanisms, magnitude, and likelihood of rapid methane release from the Arctic. Methane may be released by several pathways, including lakes,
wetlands, and oceans, and may be either uniform over large areas or concentrated in patches. Across Arctic sources, bubbles originating in the sediment are
the most important mechanism for methane to reach the atmosphere.
In addition to the warming effect of current forcing and emissions, methane plays a role in climatic feedback mechanisms that can exacerbate
warming and even lead to abrupt, catastrophic climate change in the future. This risk is primarily associated with the rapid release of carbon
stores in the Arctic due to warming, leading to higher atmospheric methane levels, especially in the Arctic. Warming due to higher Arctic
concentrations, in turn, leads to additional methane releases in a positive feedback cycle.
The Impact of Methane Clathrate Emissions
on the Earth System Lawrence Berkeley National Laboratory, Los Alamos
National Laboratory.
Philip Cameron-Smith, Subarna Bhattacharyya, Daniel Bergmann, Matthew Reagan,
Scott Elliott and George Moridis
Lawrence Livermore National Laboratory, Lawrence Berkeley National Laboratory, Los
Alamos National Laboratory
SPARC Meeting, Queenstown, 2014
This work is supported by the Earth System Modeling program of the Office of Science of the United States Department of Energy. U. S.
Department of Energy by Lawrence Livermore National Laboratory
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The Impact of Methane Clathrate Emissions on the Earth
System
Philip Cameron-Smith1, Subarna Bhattacharyya1, Daniel Bergmann1, Matthew Reagan2, Scott Elliott3 and George Moridis2
1
Lawrence Livermore National Laboratory, 2 Lawrence Berkeley National Laboratory, 3Los Alamos National Laboratory
Location of emission has some
effect on climate
Methane emissions
may change variability
Methane emissions change
interannual autocorrelation
Expected methane sources due to warming
WeWe
developed
a chemistry-climate
of CESM
added a fast chemical
mechanism to CESMversion
that is designed
to
There appears to be difference the interannual
variability between AE, UE, and control
The year-to-year auto correlation in southern
ocean seems to be reduced
Methane conc. increases non-uniformly
Glob
al
Arctic
10x
scenari
os
Annual temperature (K)
A
E
1
0
x
Onset of Clathrate emissions expected to be abrupt
UE1
0x(fi
Uxed)
E
1
0
x
Interannual variability in zonal-mean
temperature changes
Note that methane suppresses the specie that destroys it, so a 3x
increase in total methane emissions (10x clathrates) produces 6-8x
methane concentration increase over our control (present-day).
Temperature increase is modestly dependent on
Emission location
10x
scena
rio
Reagan, et al.,
2011
This is the sediment response to a temperature ramp of 5K for 100
years.
This emission rate is ~20% of global methane emissions.
Most of the emission comes from 300-400m depth.
% methane released to atmosphere
(no methanotrophs)
Fraction of methane that passes through
ocean is uncertain, but could be large
Auto-correlation important for uncertainty
Latitude
LEFT: Zonal mean surface temperature increase over control
(AE=Red, UE=Blue, UE10x(fixedCH4)=Green, 2xCO2=Cyan,
4xCO2CMIP=Magenta). RIGHT: same data, but expressed as
%difference for AE over UE for different regions (GL=globe,
SP=south pole, LL=low latitudes, NP=north pole). The error bars are
the uncertainty in the mean. The UE simulation is slightly warmer
than the AE scenario for almost all latitudes except the Arctic. The
modest difference in the Arctic seems to be a compensation between
increased warming from extra methane in AE, with greater poleward
heat transport in UE.
Variability decreases for El Nino and Sea-ice
AE10x
UE10x
UE10x(fixedCH4)
2xCO2
4xCO2CMIP
Methane is consumed in the ocean by methanotrophs.
But, bubble plumes may inject methane to upper ocean levels which
will allow faster release to the atmosphere.
•
Couple our atmospheric methane model to ocean and
permafrost methane codes.
Determine emission amplification factors, ie the amount of extra
methane released due to the warming from the original methane
emission (cross-amplification between reservoirs will also
occur).
Assess the likelihood of runaway warming (aka, the clathrate
gun).
Participate in future methane related model intercomparisons
(we participated in the Atmospheric Chemistry-Climate Model
Intercomparison Project (ACCMIP), which helped confirm and
debug our model chemical behavior, and resulted in several
papers).
Acknowledgements
We acknowledge the contribution of our collaborators, who have
primary responsibility for the ocean model (S.Elliott & M.Maltrud,
LANL) and sediment model (M.Reagan & G. Moridis, LBNL). We
also acknowledge J.Stolaroff (LLNL) for including us in a review for
technical mitigation measures for methane.
Annual-mean surface ozone increase due to clathrate emission (vmr)
Methane is an important precursor for chemical smog, and the 1x and
10x clathrate emissions increase ozone concentrations by ~5ppb and
~35ppb in polluted regions, respectively. The ozone increase is likely
to be even greater during pollution events.
Future plans
•
•
10x
scenari
os
Seafloor
Months since start of simulation
The dots are the variability in the means of each time window of the
specified length within the 400 year simulations (with different starting
years when possible). The circles are the standard error formula
without any autocorrelation correction. The difference is due to autocorrelation.
•
10x
scen
ario
50 m
depth
150 m
depth
Red Dots: Arctic Emission
Black Dots: Control
Length of time-window (years)
There seem to be changes roughly proportional to the level of global
radiative forcing at several latitudes (indicated by arrows). In many
cases the decreases are clearly related to sea-ice. In the zonal
means, the difference between AE and UE is hard to distinguish from
the uncertainty (1 sigma ~ 0.04). Note: the various 4xCO 2 runs are
very short, so their variability is much more uncertain.
Ozone increases most in polluted regions
Elliott, et al., 2010,
2011
Lattitude
The lag-1 autocorrelation of the annual time series shows the degree
of predictability from one year to the next. It shows the importance of
the long-term climate modes, and is also important for quantifying the
uncertainty in time-series quantities. Red = AE, Blue = UE, black =
control, black-dash = UE10x(fixedCH4), thin colored lines are Monte
Carlo realizations with control statistics, to indicate confidence. The
three methane runs show decreased predictability in southern ocean.
Uncertainty in surface
temperature (K)
Clathrates are methane locked in a water ice structure.
ESAS = East Siberian Arctic Shelf (methane under submerged
permafrost)
10x
scenario
s
Ratio of standard deviations of
zonal-mean surface temperatures to control
Stolaroff, et al.,
2012
The increased methane variability in AE over UE (from the effect of
synoptic weather patterns on the clathrate plumes) seems to affect
the PDFs of the annual temperature. The effect on the Arctic isn’t as
noticeable because it is already a highly variable region.
Note that the mean, std. dev., and skewness all seem to be affected.
10x
scenari
os
Lag-1 autocorrelation coefficient
handle methane . We simulated over 600 years (after spinup) under
present-day conditions with 1x and10x expected clathrate emissions
(AE), and the same amount of extra emission spread uniformly over
the globe (UE). We used an active ocean to see the coupled
chemistry-climate response.
PDF of annual temperatures
Warming may release methane from
large Arctic reservoirs
The spatial pattern of the change in the standard deviation of the
annual mean surface temperatures looks like it is mostly a function of
the radiative forcing in the scenario.
This research used resources of the National Energy Research
Scientific Computing Center, which is supported by the Office of
Science (BER) of the U.S. Dept. of Energy under Contract No. DEAC02-05CH11231
SPARC Meeting, Queenstown, 2014
Warming may release methane
from large Arctic reservoirs
Expected methane sources due to warming
• Warming may release methane
from large Arctic reservoirs
Clathrates are methane locked in a water ice structure.
ESAS = East Siberian Arctic Shelf (methane under submerged
permafrost)
Stolaroff,
et al.,
2012
Onset of Clathrate emissions expected to be abrupt
Reagan, et al.,
2011
This is the sediment response to a
temperature ramp of 5K for 100
years.
This emission rate is ~20% of
global methane emissions.
Most of the emission comes from
300-400m depth.
This is the sediment response to a
temperature ramp of 5K for 100 years.
This emission rate is ~20% of global
methane emissions.
Most of the emission comes from 300-400m
depth.
Fraction of methane that passes through
ocean is uncertain, but could be large
Methane is consumed in the ocean by methanotrophs.
But, bubble plumes may inject methane to upper ocean
levels which will allow faster release to the atmosphere.
Location of emission has some effect on climate
We developed a chemistry-climate version of CESM
We added a fast chemical mechanism to CESM that is designed to handle methane . We simulated over 600
years (after spinup) under present-day conditions with 1x and10x expected clathrate emissions (AE), and the
same amount of extra emission spread uniformly over the globe (UE). We used an active ocean to see the
coupled chemistry-climate response.
Note that methane suppresses the specie that destroys it, so
a 3x increase in total methane emissions (10x clathrates)
produces 6-8x methane concentration increase over our
control (present-day).