Climatology of the southeastern United States continental shelf waters

Abstract

Data from 2872 hydrographic stations have been used to determine the oceanographie climatology of the southeastern United States continental shelf waters. The data were sorted by each degree of latitude and by depth into three zones (0–20 m, 21–40 m, 41–60 m). Inner shelf water temperatures were similar to adjacent land air temperatures, while outer shelf temperatures were moderated by the Gulf Stream. Minimum and maximum water temperatures occurred in Georgia and South Carolina inner shelf water. Bottom temperatures were unusually low off Florida in the summer probably because of shelf break upwelling. Surface salinity was lowest adjacent to the rivers and reached minimums in the spring at the time of high runoff. An exception to this occurred in the fall, when strong southward winds apparently advected low salinity coastal water southward and offshore flow was restricted. Heat flux was calculated from changes in monthly mean depth‐averaged inner shelf water temperatures. Heating occurred from March through July with maximum rates of 103 W m−2. Cooling occurred from October through February with maximum rates of −90 W m−2. Bulk stratification was estimated from the difference in near‐surface and near‐bottom monthly mean density. In the spring, stratification increases in inner shelf areas because of decreasing winds and increasing heat flux and runoff. By summer the whole shelf is highly stratified reflecting the contrast between high surface water temperatures and cooler bottom waters. Highest bulk stratification is found over the outer shelf. Stratification decreased with the approach offall with the associated cooling and high winds. Mean flow at midshelf was northward and appears to be produced by an along‐shelf slope of sea level of oceanic origin. Data are available with entire article on microfiche. Order from the American Geophysical Union, 2000 Florida Avenue, N.W. Washington, D.C. 20009. Document C82‐002; $2.50. Payment must accompany order.

Routes and rates of larval fish transport from the southeast to the northeast United States continental shelf

“…CTD (conductivity, temperature, depth) casts and XBT (expendable bathythermograph) drops were made, and observed temperature-salinity (TS) properties were compared to the TS properties of the water masses typically observed in the SEUSCS and southern NEUSCS during springtime (Atkinson et al 1983;Churchill et al 1993). To gain a sense of the speed of entrained SEUSCS * Crossed from the Gulf Stream to the northeast U.S. continental shelf edge in a discharge of water emanating from a Gulf Stream meander.…”

“…The southeast U.S. continental shelf (SEUSCS) extends from the Straits of Florida to Cape Hatteras and contains relatively warm, salty water (Atkinson et al 1983). The northeast U.S. continental shelf (NEUSCS) reaches from Cape Hatteras to Georges Bank and contains relatively cold, fresher water (Beardsley et al 1985;Aikman et al 1988;Churchill et al 1993).…”

Benthic primary productivity on the Georgia midcontinental shelf: Benthic flux measurements and high‐resolution, continuous in situ PAR records

“…The timing of reduction in benthic PAR flux in fall correlates very well with an observed increase in wave height (Figure 7d). Increased significant wave height in the R2 record accompanies the fall transition, when there is a shift from the light to moderate southeasterly winds typical of summer to much stronger north-to-northeasterly winds associated with autumn cold fronts [Atkinson et al, 1983;Blanton et al, 2003]. Although elevated mean values are observed from the February to September time period, it is important to note that there is significant variability throughout the year with numerous zero to near-zero values in all seasons.…”

Shelf edge tide correlated eddies along the southeastern United States

“…Secondly, SETC eddies could transfer momentum and define the process by which the GS directly affects subtidal variability on the outer shelf. While the correlation between subtidal variability on the outer shelf and Gulf Stream variability is well-known [Atkinson et al, 1983], the physical processes to support causation have not been defined. As a pulsed process affecting momentum transport between the GS and the outer shelf, they should be represented in horizontal eddy diffusivities along ocean basin boundaries -a topic of interest since Munk [1950], continuing to the present [Jochum et al, 2008].…”

“…[2] In the southeastern United States, Gulf Stream (GS) variability correlates strongly with energetic alongshelf currents on the outer shelf [Atkinson et al, 1983]. Semidiurnal tides are also large, with an M 2 maximum on the Georgia shelf falling from 0.4m/s midshelf to 0.3 m/s on the outer shelf [Pietrafesa et al, 1985;Blanton et al, 2004].…”