Dear All,
Here you find the text that was put together in October in Brussels re the review paper. Further below I
made a more detailed outline how the paper could be structured and which questions might be asked and
answered. These are just my ideas which I put down to stimulate and get the discussion going.
Start with summarising what’s happening with methane in the atmosphere. Sources, budgets, what is
known, what isn’t.
PERGAMON contribution: assessing the fluxes of methane to the atmosphere from Arctic sources,
including the processes/ feedbacks that regulate these fluxes.
‘what do we know, how do we know it, what is changing´
Overarching aim of this paper: We want to come up with ‘best estimates’ of present-day fluxes, and
uncertainties. Also need to identify which fluxes are most vulnerable to change- e.g. with temperature
Draft Outline:
1. Define Arctic, scope of this paper
2. WG A (Gas hydrate in permafrost and sub-seafloor) Some potential issues include putative fluxes
reported for the Siberian Shelf) Include work on e.g. transmission of sub-seafloor CH4 to the
surface & response to perturbations of e.g. temperature. Also terrestrial permafrost, as well as
permafrost under the oceans
3. WG B1 (sub-seafloor processes, fluxes across the seafloor interface)
4. WG B2 (transmission of methane from the seafloor to the atmosphere) What conditions lead to
methane release to the atmosphere?
5. WG C1: (Terrestrial methane fluxes, including lakes) E.g identification of sources, processes, use
of land-surface models for predicting change.
6. WG C2 Atmosphere state of the art. Discuss especially the Arctic
7. Models: how well is methane modelled? What are the main/most important unknowns? Most
poorly modelled/ currently ignored processes? Why do models differ? Verifications and criteria.
8. Methodologies: major approaches, their shortages and advantages. Verifications. which
measurements can we make well, which need improvement? What level of observations are
required, in time and space?
9. Fluxes: Need a table stating best estimates for different fluxes, including uncertainties (possibly
incorporate into relevant chapters, or dedicated Chapter targeted to IPCC)
Uncertainties and “best” estimates of present and
future methane fluxes in the Arctic
it would be important to address the possible mitigating measures (either in last section, or in last parts of
specific sections) and to assess the relative contribution of various factor and processes (up-to-date
integration of our knowledge) - IO
Introduction
The Arctic is changes rapidly and these changes might create a positive feedback to global warming. Do
we have to bother (or who has to bother) if the Arctic becomes warmer, ice is melting and methane is
increasing. Small review of temperature development prognoses for the future.







focus on terrestrial and marine methane fluxes and their signatures in the atmosphere
highlight the needs of more permanent monitoring stations in the ocean, in wetlands, shallow
lakes as well as in the atmosphere (before that, spatial and temporal heterogeneity should be
addressed, as well as other problems in accuracy of flux assessments-IO)
explain what the most pressing questions are and why we currently have problems to give good
global flux estimates that most of us can agree.
Are we doing too little data integration and GIS based up-scaling of very precise but locally and
timely limited measurements
How can we make bottom-up and top-down modelling approaches come closer together
With increasing warming, will the
Introduce the coming 7 topics
1 Fluxes from gas hydrates and marine /terrestrial permafrost
The main question here as I see it to which extend marine gas hydrates need to be considered
as additional source. Some questions that need to be addressed could be:







What are the general ideas where and how gas hydrates occur linked to permafrost
(Here a good differentiation would be valuable, as some times the definition / concept of
permafrost and gas hydrates seemed to be mixed)
How can we estimate gas hydrate occurrence from seismic studies, where are the
limitations
How much gas hydrate exists offshore and onshore linked or not linked to permafrost
How quickly can a thermal pulse decompose gas hydrates (in relation to…., e.g.
location, depth, ambient conditions), do we have enough data; if not, where do we need
more data
Can 4D seismic measurements help to investigate the processes in the sub-seafloor and
monitor gas hydrate decomposition before gas comes out at the surface (appearance of
free gas)
What are the difficulties in mapping permafrost offshore
Effect of water depth on fate of the emitted methane and its flux to the atmosphere in
marine systems


How long could it take from atmospheric warming to final gas hydrate melting?
How will gas hydrates melt (fast, slow, free gas, dissolved gas)?

2 Biogeochemical sub-seafloor processes, fluxes across the seafloor/ocean
interface
This rather focused topic on marine methane fluxes into the water column is good covered with the
expertise we have in the PERGAMON group:



Review on the biogeochemical processes in the sediment and sediment surface (I think Tina
Treude wrote already about this for a GRID-Arendal report).
Are the processes and rates the same in the Arctic as on other seeps sites, if yes can we confirm
this with data, if we do not have data why do we think it is similar/not similar (consider key factors
affecting the fluxes)
Will the benthic filter kick in and can it cope with a possible strong and localised increase of
methane fluxes (not much is known / published on arctic methane oxidation in sediment or
water column. Thus we will have to interpolated data of general microbial activities in the arctic
with data on methane oxidation in non-arctic areas)






Time scales of increasing methane release and can the biological filter (both in sediments and in
water column) cope with increasing methane fluxes that will increase over decades Which
organisms are consuming methane in the seafloor and how does it work?
What do we know about the activity of these organisms in arctic regions? Does it make any
difference if Arctic or not? If yes, what are (or could be) the differences? Any adaptations
(necessary)?
How fast will present AOM consortium react to increases in methane fluxes (activity, growth)?
How long will it take to install AOM organisms in sediments that were primarily devoid of methane
and AOM consortia?
How will the benthic methane filter react to different transport mechanisms of methane (dissolved
diffusive, dissolved advective, small gas bubbles, vigorous gas venting)?
Will small temperature increases affect AOM activity (is it relevant)?
Will the development of a cold-seep communitiy have any effect on established non-seep
communities? Will a cold seep community (including chemosymbiotic clams, tubeworms etc)
establish at shallow depth or will they be outcompeted by organisms feeding on organic matter
from photosynthesis?

3 Transmission of methane from the seafloor (and freshwater/estuarine
sediments) to the atmosphere
This rather focused topic on marine methane fluxes into the water column is good covered with the
expertise we have in the PERGAMON group. However, we have still some important topics, one is a
proper and “global” applicable bubble dissolution model as well as standardizing hydroacoustic bubble
monitoring with ships and the respective quantification of fluxes. (methods and models should be
considered first)
 methods of flux assessments
 currently available bubble dissolution models and their Limitations
 Importance of ebullition vs. diffusive gas fluxes
 Important of short term plume release of bubbles
 Importance of microbial CH4 oxidation vs. Current/internal wave distribution
 Impactions of CH4-oxidation towards ocean acidification, does it happen
 Can the Arctic shelves become a significant transmitted towards the atmosphere and at what
conditions, what would be the worst case scenario









How to measure sea air gas exchange, is Eddy Covariance and option for ships (when on
station?)
Would a link with airplane flights in parallel to ship measurements be advisable for shallow areas
where we know that we have at least some fluxes.
Where are areas to test this (one is certainly offshore Santa Barbara, what about the Black Sea
shelf or Mediterranean; Spitzbergen, or other arcitc site, some swedish lakes, Canada, Russia
certainly would be interesting but difficult)
Physical transport and dilution mechanisms of methane in the water column
Which organisms are consuming methane in the water column and how does it work?
How are arobic methanotrophs acting in the Arctic? Any adaptations? Activity slower or normal?
How fast could aerobic methanotrophs react to a sudden increase in methane flux through the
water column?
Could aerobic methane oxidation be a potential source for ocean acidification?
Coild aerobic methanotrophs become an important new source of organic carbon in pelagic Arctic
food chains?

4 Terrestrial methane fluxes, including lakes
Present the different sources which as far as I understood can be measured quite accurately but have
strong temporal changes and the extrapolation to large areas is not easy.



What are the problems in extrapolation fluxes spatially and in time
How the bottom up approach starting with wetland measurements, tower measurements, airplane
measurements and finally satellites be better linked to fit with global atmosphere models (or does
it fit?)
Ebullition and dissolved fluxes in lakes, how to extrapolate, would a large scale research
campaign shade more light into this (either move to marine or separate in specific chapter - IO)
5 Atmosphere state of the art
satellite assessments? - IO
6 Models
Explain the different models needed, atmosphere, ocean circulation, vegetation, ice cover, …




How well is methane modelled?
What are the main/most important unknowns?
Most poorly modelled/ currently ignored processes?
Why do models differ
7 Methodologies
8. Integration, predictions, and possible mitigating measures - IO
9. Conclusion
1. Where are the main problems in our current knowledge for “correct” local, regional and global
methane flux measurements, spatial extrapolations and estimates of future fluxes.
2. How does the potential (maximum possible) methane release compares to other global
(anthropogenic) sources.
3. Make a clear statement what we should do to slow down the methane increase in the
atmosphere, do we have prepare Geo-Engineering strategies to prevent bubble expulsion from
the Arctic shelves, capture methane from wetlands; Capture when the water body are ice
covered?
4. Where are the areas/“exact” locations where additional monitoring is needed. Would intense
airplane campaigns help to close gaps at least in atmospheric monitoring. How should this look
like (how much would it cost, who could be involved, who could lead a global initiative)
Appendix
A1 Compilation of fluxes
Table with fluxes for the different “chapters/topics” stating best estimates for different fluxes, including
uncertainties. Might overlap with what will be published by GRID-Arendal