Fig. 2: Isotope (¹⁴C and δ¹³C) composition of all carbon forms.

a Dissolved organic carbon (DOC), particulate organic carbon (POC), and dissolved carbon dioxide (CO₂) and methane (CH₄) across all sample locations; the bars on the left indicate the ¹⁴C (not δ¹³C) values (mean ± 1σ) of the five sources used in the isotope mass balance; ¹⁴C ages are indicative (years before present; yBP); δ¹³C signatures of potential carbon sources are indicated at the top: modern atmospheric CH₄ (ref. ⁴⁵), bacterial methanogensis and bacterial methyl-type fermentation²⁴, aquatic (permafrost freshwaters) respiration CO₂ (refs. ^19,26), soil respiration CO₂ and soil organic matter from the study site (including Yedoma soils)²², and modern atmospheric CO₂ (ref. ²⁵). b ¹⁴C signatures across all carbon forms by sample location; the thick horizontal lines represent the median, limits of the boxes represent upper and lower quartiles, whiskers extend to 1.5 times the interquartile range, dots represent all data points, letters indicate statistical differences between the sample locations using ANOVA (see Methods).