IOUSP

Carbon flux and sedimentation dynamics on the Northwest Atlantic margin.

25 de março, quarta-feira, 16:30

Dra. Cynthia Pilskaln, Professor of Oceanography, UMass Dartmouth School for Marine Science and Technology, USA

Local: Anfiteatro do IOUSP

Continental margins play a substantial role in the global carbon cycle due to their elevated annual rates of carbon fixation, remineralization and burial as compared to the adjacent interior ocean. Compilation of U.S. east coast margin data sets of particulate organic carbon (POC) fluxes, resuspension, offshore advection, and sediment accumulation rates reveals that the Gulf of Maine contributes significantly to the total east coast domain budget of POC export and burial. Our regional synthesis indicates that although a majority of the surface-produced, sinking POC is rapidly remineralized in the relatively shallow Gulf of Maine water column, sedimentary carbon accumulation is 2-3 times larger than that reported for the Mid- and South Atlantic Bight regions. Additionally, a large, previously over-looked carbon inventory exists in benthic nepheloid layers (BNLs) on the shelf. The persistent BNLs, exhibiting elevated biological activity, represent geochemical transformation layers which modulate the balance between carbon remineralization, benthic delivery and offshore transport. Estimated potential lateral movement of the shelf BNLs to the adjacent deep North Atlantic slope represents an offshore input of approximately 11 Tg C per year. Multi-year, time-series particle fluxes collected in the Gulf of Maine reveal decadal decreases in carbon delivery coincident with surface warming and decreasing salinity. Near-bottom pCO2, pH, DIC, total alkalinity and particle beam attenuation data sets provide evidence of seasonal carbon remineralization driven by coupled biological-carbonate pump dissolution reactions occurring in shelf benthic nepheloid layers.