HR: 09:05h
AN: OS51D-05    [Abstracts]
TI: Using the Silica Cycle to Re-assess the Role of Continental Margin Systems in the Deep Biological Carbon Pump
AU: * Jahnke, R A
EM: rick@skio.peachnet.edu
AF: Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411 United States
AU: Jahnke, D B
EM: djahnke@skio.peachnet.edu
AF: Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411 United States
AB: Predictions of future climate require that the long-term partitioning of carbon dioxide between the oceans and atmosphere be estimated. Deep sea sediments receive only a small amount of organic carbon and waters above the base of the main thermocline exchange with the atmosphere on time scales of generally less than a few decades. Therefore, the most important oceanic reservoir for carbon storage on climate-change time-scales is oceanic deep water. Studies of the biological pump must focus on those ecosystems that supply the majority of the flux to the deep ocean, i.e. to below approximately 1000 m. Previous studies of deep organic fluxes based on benthic flux compilations have indicated that regions near continental boundaries, particularly those that experience significant, wind-driven coastal upwelling, supply a disproportionately large proportion of the organic carbon to the deep ocean. Margin systems in general were estimated to account for approximately 1/2 of the total deep biological pump. Despite this potential role, process studies of carbon fluxes have not focused on these environments. Because processes such as benthic exchange, iron input from shelf sediments, denitrification, and nepheloid layer transport are unique to margin systems, open ocean process studies may not provide an accurate assessment of carbon dynamics in margin settings. Recent publications report that 1. POC and opal fluxes are not strongly correlated in open ocean sediment trap samples, 2. measured opal fluxes in traps are less than those inferred from a global circulation model (GCM) and 3. silica burial is greater in continental margin sediments and less in the southern ocean than previously reported. Here we present a compilation of benthic flux chamber results from margin systems that confirm a strong correlation between POC and opal fluxes, consistent with ecological models. These results support the conclusion that there is a strong link between organic carbon and Si cycles and suggest that the discrepancy between GCM and open ocean trap fluxes may be balanced by an opal flux along continental margins. Taken together, these results support previous benthic flux studies that suggest that continental margin systems significantly contribute to the deep biological carbon pump.
DE: 4804 Benthic processes/benthos
DE: 4805 Biogeochemical cycles (1615)
DE: 4806 Carbon cycling
DE: 4203 Analytical modeling
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting