HR: 1340h
AN: OS13A-0504    [Abstracts]
TI: Characterizing the Chemical Composition of the Columbia River Plume: the use of Silicic Acid, Nitrate, Manganese and Salinity as Tracers of Sources of Waters Contributing to the Plume.
AU: * Bruland, K W
EM: bruland@ucsc.edu
AF: Institute of Marine Sciences University of California Santa Cruz, Earth and Marine Science Building 1156 High Street, Santa Cruz, CA 95064
AU: Aguilar-Islas, A M
EM: aaguilar@ucsc.edu
AF: Institute of Marine Sciences University of California Santa Cruz, Earth and Marine Science Building 1156 High Street, Santa Cruz, CA 95064
AU: Lohan, M C
EM: mlohan@es.ucsc.edu
AF: Institute of Marine Sciences University of California Santa Cruz, Earth and Marine Science Building 1156 High Street, Santa Cruz, CA 95064
AB: The RISE program is examining the influence of the Columbia River plume on the coastal waters off Washington and Oregon. It is important to define the macro and micro nutrient chemistry of the plume as it enters these coastal waters. Low salinity waters of the Columbia River are encountered just a short distance inside the mouth of the Columbia River estuary. These low salinity waters (salinities of 1 to 5) are low in nitrate (3 to 10 $\mu$M), high in silicic acid (140 to 160 $\mu$M), high in dissolved manganese and relatively high in dissolved iron. Within a remarkably short distance of exiting the mouth of the estuary into the coastal waters, the plume has attained salinities of roughly 13 to 22. The source of seawater that is entrained together with the river water in this near-field mixing regime to form the Columbia River plume can be defined using silicic acid, nitrate, manganese and salinity as tracers. During June and July of 2004, it appears that the seawater being initially entrained with the plume is subsurface, high salinity (>33), nutrient rich (nitrate 25 $\mu$M and silicic acid 35 $\mu$M) water. This is particularly important for the macronutrient nitrate, as this adds a substantial amount of additional nitrate to the plume. The plume water then advects and mixes further away from the source. The combination of these same tracers is useful in identifying the far-field mixing as well. We will present examples of these processes and tracers using data from the 2004 RISE cruises.
DE: 4805 Biogeochemical cycles (1615)
DE: 4808 Chemical tracers
DE: 4815 Ecosystems, structure and dynamics
DE: 4219 Continental shelf processes
DE: 4271 Physical and chemical properties of seawater
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting