HR: 16:35h
AN: OS54A-02    [Abstracts]
TI: Nitrogen and Phosphorus Fluxes in the Gulf of California: Geostrophic Approach
AU: * Bustos-Serrano, H
EM: hbustos@uabc.mx
AF: University of Miami. Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Cswy, Miami, Fl 33149, United States
AU: * Bustos-Serrano, H
EM: hbustos@uabc.mx
AF: Universidad Autónoma de Baja California. Facultad de Ciencias Marinas., Km. 103 Carretera Tijuana-Ensenada, Ensenada, BC 22890, Mexico
AB: Continental margins exert a strong influence on global biogeochemical cycles. There have been relatively few studies to quantify either the magnitude or nature of temporal variability in material fluxes. Nutrient fluxes studies at the mouth of the Gulf of California (GC) are needed to estimate values from direct measurements. From 1995- 1999 during five cruises covering all seasons, seawater samples were collected and measured the nutrient content from the surface to the bottom (some deeper than 2500 m) from a repeated hydrographic sections at the mouth of the GC. This chemical and physical database is unique because it covers an area with important biogeochemical signs, which has been detected as one of the highest in primary productivity of the world oceans. These sections are perpendicular to the coastlines of the Mexican states of Baja California Sur (BCS) and Sinaloa. We choose only one section, with very dynamic surface water. Strong geostrophic currents appear in February 1999 with temperatures of 20±1.5°C; salinity 35.091°0.156; pH 8.16°0.13; phosphate 0.85°0.42μM, nitrate+nitrite 2.35°2.94μM, and ammonia 2.00°1.25μM (average ° standard deviation). The geostrophic velocities were computed from high-resolution CTD sections across the entrance to the GC. During winter and spring, the outflow occurred near BCS and the inflow occurred either through the center of the section and/or along the Sinaloa coast. Both inflow and outflow cores were 45 km wide and extended deeper than 700 m. Summer and fall showed a complex pattern, alternating cores of inflow and outflow but with inflow along Sinaloa on all cruises. The maximum flow into the Gulf occurs during May in the center of the section while outflow was concentrated along BCS. The section mean geostrophic velocity was composed of two alternating cores of inflow and outflow. The two cores that were adjacent to either coast were broader and contained the highest inflow (0.40 m s-1) and outflow (-0.25 m s-1) velocities, supporting the general idea of inflow along the Sinaloa and an outflow along BCS. The highest nutrient fluxes occur during El Niño conditions in November 1997 with outflows as high as 54.5 Tg yr-1 for phosphate, 43.0 Tg yr-1 for nitrate+nitrite and 31.7 Tg yr-1 for ammonia, this values were at least three times higher than in February 1999.
DE: 4223 Descriptive and regional oceanography
DE: 4243 Marginal and semi-enclosed seas
DE: 4522 ENSO (4922)
DE: 4805 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912)
DE: 4845 Nutrients and nutrient cycling (0470, 1050)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly