A Sedimentary record from Burial lake, AK, reveals a covariance between erosion rate, permafrost thaw, and climate

The interaction between permafrost thaw and soil erosion may meaningfully influence the Arctic ecosystem through re-distribution of sediment and soil organic carbon, which may also influence global climate. Although permafrost thaw generally increases soil erosion, the relations between permafrost thaw, soil erosion, and climate are yet to be quantified. To quantify these relations, we analyzed sediments from Burial Lake, an Arctic lake with a small watershed nested in the Brooks Range, AK. Erosion rates for the lake's watershed were reconstructed from sedimentation rate, lake area, and watershed area. Additionally, age offsets (difference between a bulk sediment age and the sediment's depositional age approximated from macro-fossils), which indicates the presence of old carbon sourced from thawed permafrost, were calculated from the lake's sedimentary record of 36 ka. Results show a rough correlation between age-offset and erosion rate, both of which appear to respond to local and regional climatic changes. This correlation likely reflects increased erosion rate and sediment flux in warm periods when the active layer thickens. Both erosion rate and age-offset are high during the mid-Wisconsin interstadial (past interglacial period) and erosion rate is low during the Last Glacial Maximum. During the recent interglacial period erosion rate shows long term increase with short term fluctuations, while age-offset only shows short term fluctuations similar to those observed in erosion rate. A particularly large peak in age-offset occurs during the mid-Wisconsin interstadial. We find that paleo-erosion rate, age-offset, and summer temperature generally covary, where age-offset responds differently to the mid-Wisconsin interstadial compared to the recent interglacial. This suggests that erosion and transport of old carbon from thawed permafrost is not only a function of climate and may dependent on additional factors such as vegetation cover, changes in sediment sources, or the erosional history of the watershed.