A 45 THOUSAND YEAR RECORD OF AGED CARBON DYNAMICS IN ARCTIC ALASKA IDENTIFIED USING RADIOCARBON AGE-OFFSET FROM LAKE E5

The timing and mechanisms of permafrost thaw and erosion prior to human influence provide essential context for permafrost carbon mobility under arctic warming. Because arctic lake sediments archive erosional products from permafrost that age significantly on the landscape before remobilizing into the lake, the range of radiocarbon ages (age-offset) present in the lake sediment can indicate the relative contribution of ancient permafrost-derived organic carbon (OC) through time. We use age-offsets from Lake E5, northeastern Alaska, to reveal changes in the contribution of aged permafrost-derived OC deposited in the lake sediment over the last 45-thousand-years. To do this, we combine the <sup>14</sup>C dating of paired bulk sediment and plant macrofossils from the same stratigraphic layer of lake sediment and ramped pyrolysis-oxidation (RPO) <sup>14</sup>C analysis. Lake E5 revealed small age-offsets (1,580 yr) during the post-glacial period, large age-offsets (27,200 yr) during the Last Glacial Maximum, and moderate age-offsets (15,100 yr) during the MIS 3 interstadial. These temporal patterns broadly align with our recently published findings from Burial Lake, northwestern Alaska, highlighting the importance of vegetation, soil development, moisture availability, and erosional mechanisms in controlling carbon mobility in Arctic Alaska while key differences emphasize the individuality of lake basins.