The Boreal-Arctic Wetlands and Lakes Database (BAWLD) and Methane Flux Inventory: how much methane is there and where is it coming from?
Methane (CH4) emissions from the boreal–Arctic region are globally significant, but the current magnitude of annual emissions is not well defined. A limitation of many currently available circumpolar-scale land cover databases and remote sensing products is a lack of differentiation among wetland and lake ecosystems that are known to have differing CH4 emissions. For both lakes and wetlands, the coarse grouping of land covers is partially driven by limitations in remote sensing, but also a lack of a uniform classification system for organizing wetland and lake types based on their CH4-emitting characteristics. A key step to improving bottom-up estimates of CH4 emissions from the circumpolar north is to use a uniform framework for classifying distinct, CH4 emitting land cover classes and their associated flux magnitudes.
In this work I developed a synthesis of surface CH4 fluxes from northern wetlands, lakes, and uplands from ~200 published studies (Kuhn et al. 2021, ESSD). The flux synthesis was built alongside a compatible land cover dataset (Olefeldt et al. 2021, ESSD), sharing the same classifications. We show CH4 fluxes can be split by broad land cover characteristics. The dataset is useful for comparison against new field data and model parameterization or validation. You can find the BAWLD map here along with the flux dataset here.
For our next steps, I will use the flux synthesis to develop statistical emission models that I will extrapolate over the Arctic-Boreal region using the Boreal-Arctic Wetlands and Lakes Dataset map. We will also explore future scenarios of warming an land cover changes to assess the sensitivity of methane emissions to climate change. Coming spring 2024!
In this work I developed a synthesis of surface CH4 fluxes from northern wetlands, lakes, and uplands from ~200 published studies (Kuhn et al. 2021, ESSD). The flux synthesis was built alongside a compatible land cover dataset (Olefeldt et al. 2021, ESSD), sharing the same classifications. We show CH4 fluxes can be split by broad land cover characteristics. The dataset is useful for comparison against new field data and model parameterization or validation. You can find the BAWLD map here along with the flux dataset here.
For our next steps, I will use the flux synthesis to develop statistical emission models that I will extrapolate over the Arctic-Boreal region using the Boreal-Arctic Wetlands and Lakes Dataset map. We will also explore future scenarios of warming an land cover changes to assess the sensitivity of methane emissions to climate change. Coming spring 2024!
How will warming and permafrost thaw influence methane emissions from northern lakes?
Methane (CH4) and carbon dioxide (CO2) emissions from small lakes are globally significant, yet highly uncertain and our understanding of how CH4 and CO2 emissions from small lakes in the north will change with warming and permafrost (i.e., frozen ground) thaw is not well known. In this study, we measured emissions from 20 lakes across a 1,600 km climate and permafrost gradient. I used a variety of field and statistical modeling techniques, including a portable greenhouse gas analyzer, bubble traps, water chemistry, and radiative forcing models. Our results show that CH4 and CO2 emissions followed opposing trends along a north-to-south gradient. We show that increasing CH4 emissions are strongly associated with warmer temperatures while decreasing CO2 exchange is linked to shifts in hydrology and within-lake primary productivity brought on by the absence of permafrost. Our results indicate small northern lakes have the potential to take up more CO2, but greater increases in CH4 emissions will outweigh CO2 uptake (Kuhn et al. 2021, AGU Advances)
Parallel projects led by UAlberta graduate student, Lauren Thompson, and Cambridge University undergraduate, Johanna Winder, explore methylmercury and microbial dynamics in these same lakes. We look forward to sharing those articles soon! |
Zooming in on microbes: who is there and who is active in subarctic lake sediments?
For my NSF biology postdoc research, I am exploring the role of methane-producing microbes (methanogens) in regulating methane emissions from different lake types in northern Sweden. I will be using field and laboratory techniques in hand with metagenomic and metatranscriptomic analysis to see if certain types of methanogens in lake sediments respond differently under warming scenarios. I am excited to return to Abisko and Stordalen mire where I conducted research as a Fulbright fellow in 2016! You can learn more about this ongoing project here or through this University of New Hampshire media release.
"Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation."
"Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation."
Permafrost thaw and peatland lakes
Thermokarst lakes, lakes impacted by the physical effects of thawing permafrost (including ground subsidence and lake expansion) are well-documented hotspots of CH4 emission. However, little is known about CH4 emissions from peatland thermokarst lakes, despite the widespread presence of peatlands across the northern landscape. Understanding the fate and magnitude of peatland permafrost carbon upon thaw is crucial to constraining the impact of climate warming on northern carbon emissions. For this research, I explored the influence of permafrost thaw on CH4 emissions from a small peatland lake in northern Alberta using high frequency spatial and temporal measurements, including CH4 measurements, sediment coring, sediment chemistry, incubations, and radiocarbon analysis.
We found that CH4 emissions, particularly ebullitive (bubble) emissions, were highest from the actively thawing lake edge and were sourced from old permafrost carbon. However, total emissions from the thaw edge played only a minor role in the whole-lake CH4 budget due to the small surface area of the thaw impacted portion of the lake. Our next steps for this research is to look at the sediment redox conditions and microbial communities in the lake thaw edge compared the center and non-thaw impacted edges. Stay tuned! |