Evaluation of the Abandoned Huanghe Delta as an important carbon source of the Chinese marginal seas in recent decades
Description
The manuscript has been accepted by Journal of Geophysical Research - Oceans. Increasing organic carbon (OC) inputs from coastal erosion contribute large uncertainties to carbon cycling in coastal seas. The Abandoned Huanghe Delta (AHD) is a typical coastal erosion region, with large amounts of eroded sediments transported to the Chinese marginal seas. Here we investigated the organic geochemical characteristics of sedimentary organic matter (OM) from the heavily eroded region of AHD and estimated the OC and lignin fluxes caused by coastal erosion. The eroded sedimentary OM was characterized by low carbon loading and low lignin content with high degradation and influenced by the Changjiang . Owing to the sharp decline in the sediment fluxes from large rivers (Changjiang and Huanghe) since the 1990s, the total fluxes to CMS decreased from 11.5 to 5.0 Mt/yr for OC and from 11.5 ×10-2 to 4.7 ×10-2 Mt/yr for lignin, therefore the contribution from the coastal erosion of AHD increased from 24±8% to 56±10% for OC and from 21±9% to 52±15% for lignin. The high proportion contributed by AHD to the Central Yellow Sea Mud area (74±11%) also accounted for the high terrestrial OC burial efficiency there (69%). Considering the different nature of OM and increasing contribution, as in this case, the significance of OC input caused by coastal erosion to the coastal seas are expected to overwhelmed that of rivers and influnce the regional and even global carbon budgets and cycles under the scenarios of global warming and sea level rising. Keywords :coastal erosion, Abandoned Huanghe Delta, Chinese marginal seas, lignin