A detached eddy in the Gulf of Mexico

This note presents some preliminary results of a still-incomplete detailed analysis of observations on the property distributions and currents in the eastern part of the Gulf of Mexico, with primary emphasis on the Eastern Loop Current. Observations were obtained aboard the R/V ALAMINOS in June 1966, 1967

Coastal studies in support of the Sargent Beach, Texas, Erosion Control Project

Source: https://erdc-library.erdc.dren.mil/jspui/One of the areas of highest coastal erosion along the Texas coast is located in the deltaic headland coastal segment of the Brazos River in the vicinity of Sargent Beach. Because of this erosion, a section of the Gulf Intracoastal Waterway (GIWW) from Cedar Lakes to East Matagorda Bay is in danger of intrusion from breaching of the narrow (less than 300-m-wide) shorefront. Owing to its deltaic origin, the beach is composed of cohesive fine-grained clay and silt material, overlain by a narrow layer of coastal peat and topped by a thin veneer of fine-grained quartz beach sand with a high percentage of shell fragments. Within the 24-year study period (1965-1989), the northeastern half of the study area measured an average erosion rate of 25 ftlyr (7.6 mlyr) and consisted of a thin sandy flat sloping beach over the clay deposit. The southwestern section has up to I-m-high clay bluffs outcropping into the surf zone and measured an average 36 ftlyr (1 1 m/yr) erosion rate. It is speculated that this high erosion rate is a result of intermittent wave cutting of large chunks of the clay bluff material. The overall erosion rate along this coast is due to a general lack of sand

Nitrate sources and sinks in Elkhorn Slough, California: Results from long-term continuous in situ nitrate analyzers

Nitrate and water quality parameters (temperature, salinity, dissolved oxygen, turbidity, and depth) were measured continuously with in situ NO₃ analyzers and water quality sondes at two sites in Elkhorn Slough in Central California. The Main Channel site near the mouth of Elkhorn Slough was sampled from February to September 2001. Azevedo Pond, a shallow tidal pond bordering agricultural fields further inland, was sampled from December 1999 to July 2001. Nitrate concentrations were recorded hourly while salinity, temperature, depth, oxygen, and turbidity were recorded every 30 min. Nitrate concentrations at the Main Channel site ranged from 5 to 65 µM. The propagation of an internal wave carrying water from ;100 m depth up the Monterey Submarine Canyon and into the lower section of Elkhorn Slough on every rising tide was a major source of nitrate, accounting for 80–90% of the nitrogen load during the dry summer period. Nitrate concentrations in Azevedo Pond ranged from 0–20 µM during the dry summer months. Nitrate in Azevedo Pond increased to over 450 µM during a heavy winter precipitation event, and interannual variability driven by differences in precipitation was observed. At both sites, tidal cycling was the dominant forcing, often changing nitrate concentrations by 5-fold or more within a few hours. Water volume flux estimates were combined with observed nitrate concentrations to obtain nitrate fluxes. Nitrate flux calculations indicated a loss of 4 mmol NO₃ m⁻² d⁻¹ for the entire Elkhorn Slough and 1 mmol NO₃ m⁻² d⁻¹ at Azevedo Pond. These results suggested that the waters of Elkhorn Slough were not a major source of nitrate to Monterey Bay but actually a nitrate sink during the dry season. The limited winter data at the Main Channel site suggest that nitrate was exported from Elkhorn Slough during the wet season. Export of ammonium or dissolved organic nitrogen, which we did not monitor, may balance some or all of the NO₃ flux.Journal ArticleFinal article publishe