The role of short-term and long-term water level and wave variability in coastal carbon budgets

We investigated soil organic carbon dynamics at three freshwater coastal sites in the Laurentian Great Lakes using a simple carbon budget box model. Long-term carbon budgets (1939–2018) were developed using aerial photography and then compared to short-term carbon export (2018–2019) developed using drone data. This study puts forth a refined coastal carbon budget model that advances previous model iterations by: (1) examining spatial variability in carbon budgets, (2) including a temporally dynamic carbon inventory term, and (3) updating the erosional term. Half of the initial carbon stock of the combined sites was lost in the 80-year study period, which is severely imbalanced with the age of those coastal habitats (400–2000 cal years BP). Major periods of carbon loss corresponded to periods of elevated water level. Short-term loss of carbon during 2018–2019 corresponded to northeasterly extreme wave events during a period of above-average water level.