Data-constrained annual carbon fluxes for Arctic & Boreal ecosystems
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Presented at the 3rd ICOS Science Conference in Prague, Czech Republic, 11-13 Sep 2018.
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Data-constrained annual carbon fluxes for Arctic & Boreal ecosystems
- 1. Data-constrained annual carbon fluxes for Arctic & Boreal ecosystems Luke Schiferl, Post-doc, Columbia University Eugenie Euskirchen, Bill Munger, Colm Sweeney, Steve Wofsy, Dona Zona Róisín Commane Columbia University rcommane@LDEO.columbia.edu
- 2. Arctic carbon in a changing climate Arctic temperatures rising at twice the global rate (Hugelius et al., 2014) High carbon content in arctic soils (1672 Pg C) ≈ 50% total below ground C ≈ 800 ppm CO2 Permafrost thaw by 2100? Winter 2017-2018 some sites didn’t freeze
- 3. Is the Arctic a carbon sink? OR carbon source? OR neutral? Increased uptake? Longer growing season? Increased respiration/CH4 emission? Permafrost thaw? etc.?
- 4. Cold season CH4 emissions ~50% total annual CH4 fluxes from eddy towers (long term) and aircraft (wider region)
- 5. Year-round Methane Fluxes show strong cold season emissions 5
- 6. 6 Respiration: CO2 aerobic (O2 rich) & Fermentation: CH4 anaerobic (O2 poor) Warming winter soil temperatures and extended Zero CurtainToolik Borehole Romanovsky, Euskirchen
- 7. Cold season emissions ~50% total annual and regional effect widespread 50% CH4 emissions during non Growing season across Arctic Treat et al., GBC, 2018
- 8. Soil temperature controls CH4 fluxes Drier, deeper active layer 8 100 days 2013 into 2014
- 9. Implications of cold season CH4 fluxes? Annual budget estimates, Process-based and Inverse models need to be updated Scot Miller, Johns Hopkins Miller et al., 2016, GBC CH4 Fluxes from Inverse Model CH4 Fluxes from mean Model Intercomparison CH4 fluxes from Inverse Model with no cold season emissions
- 10. Alaskan Tundra: Annual source of Carbon Winter emissions larger than expected, have increased since 1975 and not included in CMIP5 models Calculated regional CO2 flux by combining airborne, tall tower & eddy flux tower CO2 data with met field & satellite
- 11. WRF-STILT defines height of various layers Additional flux calculated from profiles July 3rd, 2014 November 9th, 2014
- 12. Aircraft optimized CO2 flux from inverse analysis Commane, et al., 2017, PNAS
- 13. Uptake greater in Boreal than Tundra Commane, et al., 2017, PNAS
- 14. Annual budget of CO2 Fluxes in Alaska Biomass Burning: S. Veraverbeke, UC Irvine Anthropogenic: Carbon Tracker, J. B. Miller, NOAA Commane, et al., 2017, PNAS
- 15. Long term trends in early winter respiration Commane, et al., PNAS, acceptedCommane, et al., 2017, PNAS
- 16. July mean 1988-2017 Luke Schiferl, LDEO Limited Long term trends in JULY light and temperature
- 17. July mean 1988-2017 Luke Schiferl, LDEO Limited long term trends in JULY light and temperature
- 18. Long term trends in early winter respiration Commane, et al., 2017, PNAS
- 19. Arctic carbon vulnerable to warming Regional CO2 and CH4 fluxes in Alaska calculated using unique approach incorporating eddy flux, tall towers, aircraft • AK Boreal sink, AK Tundra source of CO2 • 70% increase in Oct-Dec CO2 over 40 years at BRW • CMIP5 models: CO2 uptake too early and magnitude wrong • CH4 continues until soils completely frozen in January - appears vulnerable to warming? Methane Publications Hartery, et al., ACPD, 2017 Karion et al., ACP, 2016 Miller, et al., GBC, 2016 Xu, et al., Biogeosciences, 2016 Zona, et al., PNAS, 2016 CO2 Publications Commane, et al., PNAS, 2017 Luus, et al., GRL, 2017 Parazoo, et al., PNAS, 2016 Parazoo, et al., GBC, 2018
- 20. 2017 Flights: April - November Extending analysis into Canada PI: Colm Sweeney, NOAA Pilot: Stephen Conley
- 21. Thank you Luke Schiferl, Erik Larson, Bill Munger, Paul Moorcroft, Steve Wofsy J. Lindaas, J. Benmergui, K. Luus, R. Chang, B. Daube, E. Euskirchen, J. Henderson, A. Karion, J. Miller, S. Miller, N. Parazoo, J. Randerson, C. Sweeney, P. Tans, K. Thoning, S. Veraverbeke, C. Miller, D. Zona, B. Gioli, S. Dengel, P. Murphy, J. Goodrich, V. Moreaux, A. Liljedahl, J. Watts, J. Kimball, D. Lipson, W. Oechel rcommane@LDEO.columbia.edu Aircraft flight tracks from HIPPO 1-5 2009-2011 (pinks) and ATom 1-4 2016- 2018 (blues). ATom 1 August 2016 public ATom 2 February 2017 public ATom 3 October 2017 public in Nov ATom 4 May 2018 public in 2019
- 22. 22
- 23. Three Alaskan vegetation eco-regions
- 24. Vegetation Types in Alaska
- 25. Large range in surface water across Alaska Jennifer Watts, John Kimball, Uni of Montana
- 26. Calculating surface influence Figure Credit: Lin et al., 2002 WRF-STILT Weather Research & Forecasting Stochastic Time Inverted Lagrangian Transport Model Lin et al., JGR, 2003
- 27. polar-WRF-STILT nested grid Hendersonetal.,AtmChemPhys(2015) d1: 30 km d2: 10 km d3: 3 km Nested grid maximizes resolution over the CARVE domain Need improved met data density for model validation
- 28. Warming winter soil temperatures and extended Zero Curtain Toolik Borehole Data from V. Romanovsky, S. E. Euskirchen 28
- 29. Winter respiration overwhelming summer uptake in some areas Luus et al., 2017, GRL
- 30. 30
- 31. Regional CH4 flux from aircraft concentrations Assume uniform surface influence of CH4 Assume no CH4 from mountain tops (grey shading) Low altitude (<1500 m) No anthropogenic influence (CO < 150 ppb)
- 32. Few CMIP5 models match observed CO2 fluxes Commane, et al., PNAS, accepted Commane, et al., 2017, PNAS
- 33. Long term trends in SEPTEMBER light and temperature Luke Schiferl, LDEO September October
- 34. Long term trends in early winter respiration Commane, et al., PNAS, acceptedCommane, et al., 2017, PNAS
- 35. Analysis Framework: Measurement: Atmospheric concentration • e.g. Laser based methods: QCLS, CRDS • e.g. aircraft, tall towers, eddy flux towers Synthesis: • Transport models (e.g. WRF-STILT) • Surface emission models (e.g. Ecosystem carbon models like SiB, CASA, PVPRM, etc.), • inverse analysis… 35
Editor's Notes
- Now I’ll talk about one particular region where things are changing rapidly. Temperatures in the Arctic are changing at about twice the global average causing permafrost to thaw. Permafrost is the land that is deep frozen year round and has been for a long time. But it’s the carbon content of this soil that is causing the most concern. Much of the arctic is old peatland and it’s been estimated that it contains half of the world’s soil carbon. If all that carbon was released into the atmosphere, that’s enough to double the CO2 in the atmosphere. So the potential impact of mobilizing this carbon is huge.
- Arctic soils are generally very wet as they thaw from the top down in spring and the permafrost a few meters down holds all in the moisture in. Arctic wetlands are a globally significant source of methane to the atmosphere. Eventually the permafrost will thaw and the shelf holding the water in place disappears, how will the changing wetlands affect the methane emissions?
- To look at methane, I worked with Dona Zona and Walt Oechel at San Diego State, who have 5 short towers on the North Slope of Alaska that measure CH4 fluxes year-round across a gradient of soil moisture.
- Profiles combine to calculate spatially resolved additive flux for each month, that we add to the original CO2 flux maps. Need more respiration in early winter.
- So overall the boreal forests is a sink throughout all the years, but the tundra regions are a source. When we combine the biogenic fluxes together (in dark green here), we can see that in 2013 a really dry year in Alaska, the biogenic fluxes exceed the fossil fuel and biomass burning CO2 fluxes. But the biogenic fluxes also exceed all other fluxes in 2014 too which was a wet year.
- So overall the boreal forests is a sink throughout all the years, but the tundra regions are a source. When we combine the biogenic fluxes together (in dark green here), we can see that in 2013 a really dry year in Alaska, the biogenic fluxes exceed the fossil fuel and biomass burning CO2 fluxes. But the biogenic fluxes also exceed all other fluxes in 2014 too which was a wet year.
- Now if we look at the early winter data for a long-running tundra site run by NOAA at Barrow, we can see an increase in early winter respiration. It is tightly related with the minimum summer air temperatures. The process driving this trend is something I’ve started looking into. My main question is: Is this new CO2 being respired soon after summer photosynthesis? OR is it old permafrost carbon becoming mobile.
- Now if we look at the early winter data for a long-running tundra site run by NOAA at Barrow, we can see an increase in early winter respiration. It is tightly related with the minimum summer air temperatures. The process driving this trend is something I’ve started looking into. My main question is: Is this new CO2 being respired soon after summer photosynthesis? OR is it old permafrost carbon becoming mobile.
- So here is a summary for the Arctic carbon stories I’ve gone through today.
- As part of the NASA ABoVE program, I’m involved with two projects working on Arctic carbon. The first is a project with Bill Munger at Harvard to look at the long term trends in carbon. The second project is an Aircraft project to extend a CARVE like analysis to the wider north American boreal domain. We have flights planned for May to November this year flying on a small 2 seater aircraft. Here we have the pilot Steve Conley and the PI Colm Sweeney with the Mooney aircraft. Now, while we’ve been planning the ABoVE flights on a little aircraft, I’ve just come back from a project on a much larger aircraft.
- We can broadly break Alaska into three basic eco-regions. Tundra is low shrub-land to the west and north. The boreal region is the areas of forest in the interior. Any area that has less than 60% tundra or forest, I’ve designated as mixed here in grey. So that includes the coastal areas and some high mountains.
- North Slope and South West Tundra both a source Boreal forest is a sink
- At the time, there were no bottom-up process based models that could produce realistic CH4 emissions for us to test against. So, given there is very little else happening to methane other than surface emission in this location, I did a simple inverse calculation of the methane emission expected given the measured methane concentration and the amount of time air spent in the surface layer in the 24 hours before we sampled it with the aircraft. Now I know that seems crude but I was surprised at how well this approach worked. In the not-too-distant future I expect we will have model outputs that will enable us to pick out where these higher emissions are located.
- Now if we look at the early winter data for a long-running tundra site run by NOAA at Barrow, we can see an increase in early winter respiration. It is tightly related with the minimum summer air temperatures. The process driving this trend is something I’ve started looking into. My main question is: Is this new CO2 being respired soon after summer photosynthesis? OR is it old permafrost carbon becoming mobile.
- Now if we look at the early winter data for a long-running tundra site run by NOAA at Barrow, we can see an increase in early winter respiration. It is tightly related with the minimum summer air temperatures. The process driving this trend is something I’ve started looking into. My main question is: Is this new CO2 being respired soon after summer photosynthesis? OR is it old permafrost carbon becoming mobile.
- My overall approach combines two things: Measurements and how we interpret them. Sorry for the alphabet soup of acronyms up here. If you don’t recognize anything, please don't worry. I won’t be bringing them up again. If you do recognize anything and want more details, I’m happy to answer specific questions now or at the end? In the work I’m going to describe today, I’ve mainly used laser based gas analyzers to measure atmospheric concentrations on a platform suitable for the science question. So for example, aircraft measurements are great to get a snapshot of a large region, while tall tower measurements can run year-round but see a smaller area. To understand the concentrations we measure, we can use a variety of tools: Transport models like WRF-STILT tell us where the air came from and where it last saw the surface Surface emission estimates or models such as ecosystem carbon models like the Simple Biosphere model or CASA. And then we combine all of these tools in an inverse analysis. Now let me show you what I mean by all this with some examples.