Assessing Arctic atmospheric methane monitoring needs through synthetic data experiments

Martijn Pallandt,  MPI-BGC,  mpall@bgc-jena.mpg.de (Presenter)
Abhishek Chatterjee,  NASA GSFC GMAO / GESTAR USRA,  abhishek.chatterjee@nasa.gov
Julia Marshall,  DLR (Deutsches Zentrum für Luft- und Raumfahrt),  julia.marshall@dlr.de
Lesley Ott,  NASA GSFC GMAO,  lesley.e.ott@nasa.gov
Mathias Göckede,  MPI-BGC,  mgoeck@bgc-jena.mpg.de

Climate change is severely affecting the Northern high latitudes. Many drastic changes are expected to the environment in these regions e.g. increases in tundra fire, methane release from degrading Yedoma and (enhanced) ebullition of methane from Arctic sea shelves. Two primary methods for monitoring atmospheric carbon are through in situ observations (e.g., atmospheric towers and aircraft observations) and satellite remote sensing. In this study we perform a series of case studies to assess the capabilities of in situ towers and space-based missions to detect signals associated with expected disturbance processes.
This research follows a 3-step approach: transporting known flux estimates in a 4D atmospheric transport model, generation of synthetic observations and signal detection. Synthetic observations as well as the baseline nature runs are produced through the Goddard Earth Observing System model (GEOS). For tower measurements gaussian noise is added to synthetic observations within the acceptable measuring range for methane as set by WMO. Satellite retrievals are modelled on an integrated path differential absorption lidar, following the approach for MERLIN developed in Bousquet et al. (2018). Here, in addition to random errors, biases due to seasonality, latitudinal gradient, albedo, surface pressure and topography are considered.
We consider two disturbance scenarios: In the first scenario we simulated enhanced methane release from expected Yedoma thaw (Strauss et al. 2017). The second scenario models enhanced methane fluxes from Arctic shelf ebullition (Shakhova et al. 2010, 2014). We use a variety of signal detection metrics to differentiate between a baseline case (i.e., no perturbation) and the disturbance scenario runs, including with varying levels of signal amplification. Results show that we are able to ascertain lower detection limits both during the peak perturbation as well as the decreasing ability to detect these over time and with increased distance from the source. We compare the ability of tower and satellite measurements to detect high latitude methane changes with the goal of informing development of a more comprehensive methane observing system.

Poster: Poster_Pallandt__134_25.pdf 

Presentation Type: Poster

Session: 2.5b Results expected from future missions

Session Date: Tuesday (6/15) 12:00 PM