Toward understanding the contribution of waterbodies to the methane emissions of a permafrost landscape on a regional scale—A case study from the Mackenzie Delta, Canada

Abstract

Waterbodies in the arctic permafrost zone are considered a major source of the greenhouse gas methane (CH ) in addition to CH emissions from arctic wetlands. However, the spatio-temporal variability of CH fluxes from waterbodies complicates spatial extrapolation of CH measurements from single waterbodies. Therefore, their contribution to the CH budget of the arctic permafrost zone is not yet well understood. Using the example of two study areas of 1,000 km² each in the Mackenzie Delta, Canada, we approach this issue (i) by analyzing correlations on the landscape scale between numerous waterbodies and CH fluxes and (ii) by analyzing the influence of the spatial resolution of CH flux data on the detected relationships. A CH flux map with a resolution of 100 m was derived from two aircraft eddy-covariance campaigns in the summers of 2012 and 2013. We combined the CH flux map with high spatial resolution (2.5 m) waterbody maps from the Permafrost Region Pond and Lake Database and classified the waterbody depth based on Sentinel-1 SAR backscatter data. Subsequently, we reduced the resolution of the CH flux map to analyze if different spatial resolutions of CH flux data affected the detectability of relationships between waterbody coverage, number, depth, or size and the CH flux. We did not find consistent correlations between waterbody characteristics and the CH flux in the two study areas across the different resolutions. Our results indicate that waterbodies in permafrost landscapes, even if they seem to be emission hot spots on an individual basis or contain zones of above average emissions, do currently not necessarily translate into significant CH emission hot spots on a regional scale, but their role might change in a warmer climate.

Size Distributions of Arctic Waterbodies Reveal Consistent Relations in Their Statistical Moments in Space and Time

“…We used waterbody maps from the PeRL database by Muster et al (2017) for the assessment of waterbody size distributions. PeRL waterbody maps provide areas of open water.…”

“…Waterbodies in the Arctic range in size from very small ponds a few meters across to very large lakes covering several square kilometers (Muster et al, 2013(Muster et al, , 2017. The most abundant waterbodies in the Arctic are small and shallow; they typically are of tens of meters or less in length and less than 2 m deep (Muster et al, 2013(Muster et al, , 2017Langer et al, 2015).…”

“…Waterbodies in the Arctic range in size from very small ponds a few meters across to very large lakes covering several square kilometers (Muster et al, 2013(Muster et al, , 2017. The most abundant waterbodies in the Arctic are small and shallow; they typically are of tens of meters or less in length and less than 2 m deep (Muster et al, 2013(Muster et al, , 2017Langer et al, 2015). Although small waterbodies do not cover a large area compared to large waterbodies, they do have a significant impact on the landscape's energy and carbon (Laurion et al, 2010;Rautio et al, 2011;Abnizova et al, 2012;Winslow et al, 2014;Langer et al, 2015) balances.…”

“…The new Permafrost Pond and Lake (PeRL) database provides high-resolution (5 m or better) information on current and historical waterbody surface areas -which we will refer to as "size" throughout this paper (Muster et al, 2017). With the availability of the PeRL database we are now in a position to characterize and analyze waterbody size distributions in the Arctic, including for the first time waterbodies as small as 0.0001 km 2 .…”

Studying boundary layer methane isotopy and vertical mixing processes at a rewetted peatland site by unmanned aircraft system

“…Known sources in northern latitudes are permafrost areas (Sachs et al, 2010;France et al, 2016;Sasaki et al, 2016;Kohnert et al, 2018), the Arctic ocean (Yu et al, 2015;Mau et al, 2017) and wetlands (Bellisario et al, 1999). Each source region has a 25 unique isotopic signature, and mixing of different air masses results in a linear combination of the corresponding δ 13 C signature .…”