Data set for modeling methane fluxes of Beringian coastal wetlands

For upscaling CH4 flux estimates in Beringia during the past 20,000 years, we collected 231 present-day CH4 fluxes from coastal wetlands in the Northern Hemisphere. We combined our own flux data (27 plot measurements) from the Kenai Peninsula, Alaska with previously published data. Data were compiled from different sources (e.g. Treat et al. 2018; 2021; Poffenbarger et al. 2011; Liikanen et al. 2009; Holmquist et al. 2018; Kuhn et al. 2021). CH4 fluxes from the literature were calculated in g CH4 m-2 yr-1 for the growing season, which we set to 153 days (May to September). Each CH4 data entry was harmonized by classifying it into one of the six wetland types Saltwater, tidal regularly flooded, Temporarily irregularly flooded, Permanently to semi-permanently flooded, Seasonally flooded, Non-tidal saturated, Water-body. This resulted in a stratified pool of CH4 fluxes and allowed a bootstrapping approach to estimate uncertainty in the CH4 fluxes for Beringian coastal wetlands based on the variability of CH4 fluxes associated to the different wetland types. For each of 258 sites, the dataset includes a site description, calculated CH4 flux from this research, wetland type, wetland class, method of CH4 measurement, major vegetation type, site location, the originally published CH4 value ("orig val") in the referenced paper, original units of measurement, citation and persistent identifier for the original data source, and comments. For some of the data points no coordinates information was given in the original publication, therefore the latitude and longitude fields were left blank.