winter, a probable result of the increased mixing of the shelf waters due to stormier conditions during the fall-winter season. During the summer, the sharp gradients of temperature and salinity still occur in the seaward direction below the seasonal thermocline (Beardsley et al., 1976). Exchange of water, salt, heat, and momentum occur across the frontal zone; Wright (1976) reports parcels of coastal waters over the slope region, particularly in late summer. However, the mechanisms of transport and movement of the frontal zone are not well understood. Williams and Godshall (1977) point to evidence of a line of divergence at the 100-m isobath that may compensate for the converging fluxes at the surface usually associated with frontal

zones.

A hydrographic feature of interest is the presence in the outer shelf of the "cold band." Beginning on the Georges Bank and extending to Cape Hatteras, this band is present in the Middle Atlantic Bight from spring through early fall. The cold band acquires its temperature characteristics during the winter months when low temperatures and increased wind effects-which enhance vertical mixing-produce a fairly homogeneous (in terms of temperature) water mass over the shelf. With the onset of spring, warmer weather and lessened winds allow formation of a seasonal thermocline that separates the upper or mixed layer from the cold waters of the bottom. During the time of the year that it is present, the cold band is bounded above by the seasonal thermocline, and to the east and west by the shelfslope front and the well-mixed waters of the inner shelf, respectively (EG&G, 1981b). The advent of fall signals the demise of the thermocline and the cold band's identity. Great concern exists about the reduced mixing between the cold band and the surrounding waters. Because of this reduced mass transfer, contaminants entrained in the band may not travel beyond its boundaries, but will move along the continental shelf margin (EG&G, 1981b). Until the flushing rates of the band, the sources of its waters, and the mixing coefficients at the boundaries are better understood, however, the possible fate and effects of any entrained pollutants cannot be fully assessed.

Until recently, evidence was inconclusive as to whether the flow in the East Coast submarine canyons was up or down the axis. Trumbull and McCamis (1967) reported a down-axis flow. A flow up Hatteras Canyon was observed by Rowe (1971); transport of sediments down this canyon's axis, however, is also reported by the same author. It should be noted, though, that sediment transport is dependent on gravity and speed of the flow. EG&G (1981b) discuss various mechanisms that seemingly play an important role in the physical processes of these canyons. Internal waves, tidal effects, atmospheric forcing on the shelf and slope, and slope and shelf hydrography are all suspect in playing a significant role in the canyon's environment. Of great significance, too, may be the effect that Gulf Stream eddies may have when interacting with waters on the slope and shelf regions. According to EG&G (1981a), internal waves and tide-generated internal wave energies are focused at the canyonheads where they break, enhancing erosion and resuspension of sediments. Atmospheric forcing plays a role in the up-down canyon flow (EG&G, 1981a). Depending on the direction of the wind, upwelling pulls water up the canyon, whereas downwelling would drive the waters down the canyon's axis. Although details are lacking, heavy fishing in the vicinity of canyonheads seems to indicate that upwelling of nutrients takes place here. Atmospheric forcing effects

are stronger in those canyons close to shore; thus, the effect of this forcing in the canyons of the mid-Atlantic is greater than in the north Atlantic. The passage of a Gulf Stream warm-core eddy seems to play a significant role in a canyon's flow by pulling water off the shelf, resulting in a down-canyon flow. Study results from Lamont-Doherty (1982b) mention both up- and down-axis flow at all depths twice a day because of tidal influences. Not only currents but temperatures as well are dominated by tidal fluctuations. Topographical influences may also direct flow from the shelf into the canyons. The study also mentions down-canyon flow of bottom currents at depths of approximately 275 m, but up-canyon at sites in 600-m depths. This pattern of circulation, however, does not necessarily apply to all canyons. According to results reported in Butman et al. (1982), circulation in Lydonia Canyon, in the north Atlantic region, is more complex. summary, the canyon circulation seems to be strongly influenced not only by topographic characteristics, but also by internal waves (including tidegenerated internal waves), atmospheric forcing, and the passage of warm-core eddies.

In

The Gulf Stream plays an important role in global scale heat, momentum and mass flux. It flows east and south of the sale area, roughly paralleling the slope. The Stream's volume, flow, and persistence influence the physics as well as the chemical and biological processes in the mid-Atlantic region. The conditions and flow of the Gulf Stream are highly variable on time scales ranging from 2 days to whole seasons, and possibly longer. At all times, the flow of the Stream is toward the northeast with a mean speed of 2 kt.

The location of the Gulf Stream's western boundary is quite variable because of meanders and eddies. Meandering events of the Gulf Stream have been attributed to atmospheric forcing, or bathymetric features. Meanders can best be described as lateral oscillations of the mean flow field which are produced by migrating waves having periods in the 2-to-14 day range. With passage of a meander, the Gulf Stream boundary oscillates sequentially onshore (crest) and offshore (trough). Such meandering, depending on its phase, causes the Gulf Stream to shift slightly shoreward or well offshore into deeper waters. Meanders have definite circulation patterns and conditions which are superimposed on the statistical mean condition. As a meander trough migrates in the direction of the Stream's flow at approximately 50 to 60 cm/s, it upwells cool nutrient-rich water which at times can move on the shelf. In any case, meanders may evolve into eddies (warm- and cold-core). These boundary features move south-southwest and transport momentum, mass, heat, and nutrients to the vicinity of the shelf break.

About 5 to 10 warm-core, anticyclonic eddies that originate in meanderings of the Gulf Stream move through the continental rise and the slope waters of the proposed lease area each year. This causes, for example, in the North Atlantic region a net exchange of 10 to 20 percent of Georges Bank waters (EG&G, 1981b). Warm-core eddies have a typical radius of 100 km (63 mi) and rotate clockwise at approximate speeds of 100 cm/s (2 kt) while moving westward and southward at approximately 5 km/day (about 3 mi/day) (Lai and Richardson, 1977). They remain between the Gulf Stream and the shelf break, playing a seemingly important role in the mixing of shelf and slope waters (Morgan and Bishop, 1977). The hydrographic characteristics such as temperature and salinity (T-S) of warm-core eddies differ markedly from those of its surroundings. In the western north Atlantic, slope

waters are cooler and less saline than in warm-core eddies moving through them. Once detached from the Gulf Stream, the temperature differences between the core of the eddies and their surroundings supply the potential energy that, upon conversion, maintains the circulation (Keer, R.A., 1977). Disappearance of these temperature differences and/or coalescence with the Gulf Stream marks the demise of eddies. Fornshell and Criess (1979) surveyed the same warm-core eddy twice at an interval of 60 days. In their first survey they found, in general, that certain isotherms were found at greater depths than is normally the case in slope waters. Also observed were relatively little mixing of eddy and slope waters and a T-S range for the eddy that coincided with that of the Gulf Stream. At 3,000 m (10,000 ft), the greatest depth surveyed, very little of the eddy showed mixing with North Atlantic Deep Water (NADW). Comparison of these results with those of the second survey showed the eddy had moved 300 km to the southwest (approximately 5 km/day). They also found a decrease in the diameter and changes in the shape of the eddy; the 15 °C isotherm was found at twice its normal depth, at 1,600-m depth (4,800 ft)--the T-S diagrams showed little difference from those for NADW, and a significant amount of surface cooling which was accelerated by two storm events during the survey. The author suggests that interaction with the New England seamounts may have influenced the obvious decay that had taken place during the time interval between surveys.

As reported in Science, Vol. 198, No. 4315 by R.A. Keer, (1977), William Holland suggested that eddies, under certain contraints, respond to bottom topography. According to this article internal friction also may contribute to the decay process by drawing water from outside into the core of the eddy. As eddies decay, salt, heat, and kinetic energy are added to the surrounding environment. Also, a net transfer of water on and off the shelf may result from the interaction of eddies and the continental shelf waters. Eddies are known to push higher salinity water onto the shelf and pull fresher water off the shelf. Trying to predict the effect of eddies on spilled pollutants is, at present, mostly guess-work. According to Flier and William (1983) (In: Research in Ocean Engineering-Newsletter, University Sources and Resources, Vol. 5, No. 1, Spring 1983; MIT-NOAA), waste materials unloaded south of normal eddy tracks could be transported southwestward for long distances; if discharged within the eddy, they could swirl around, eventually finding their way into the Gulf Stream system or beyond. There could also be transport of pollutants onto the shelf regions, and in some cases, materials could be deposited behind the eddy, where, given the right set of conditions, further transport could carry them to shore.

In this region, tidal motion is semi-diurnal and rotary. The mean tidal range is approximately 4 ft (1.2 m) at Atlantic City, New Jersey. Except in shoal areas, tidal currents are generally weak in offshore regions and less than 0.1 kt over most of the shelf. In embayments and shoal areas near the coast, tidal currents can reach speeds as high as 2 to 3 kt. In Raritan Bay, tidal currents range from 1 kt in the Bay up to 3 kt in the Narrows and the Main ship channel (Bumpus, 1973). Tidal currents in the Delaware Bay range from 0.4 to 3 kt between Cape May and Cape Henlopen. the lower part of the Bay, tidal current speeds are between 0.5 and 2 kt, while speeds of up to 3 kt occur in the upper parts. As tidal currents move in and out of these basins, a component to the right of the flow influences the non-tidal flow, resulting in the piling of water on the shore to the right of the current. However, the actual circulation pattern in any area is the net result of the tidal and non-tidal currents (see Visual No. 5).

In

The highest waves in the area are observed in December, January, and February. During January, the percent frequency of waves equal to or greater than 5 ft (1.5 m) is less than 40 percent, and less than 10 percent for waves equal to or greater than 12 ft (3.6 m). There are isolated extreme events: CNA (1977) mentions waves generated by hurricanes in the Baltimore Canyon area with heights of 58, 65, and 72 ft, with return periods of 25, 50, and 100 years, respectively. Generally, extratropical cyclones generate higher waves than hurricanes. Extratropical cyclones are, for the most part, very extensive and, when coupled with a location northeast of the Middle Atlantic Bight, have the expanse of the north Atlantic Ocean for available fetch. The available fetch for wave generation depends on the trajectories followed by cyclones. Passage of the low pressure centers over land is not likely to result in waves of great heights, except possibly along the southern shore of Long Island, New York. Hurricane David's center followed an inland path from Georgia north during August and September 1979. Wave and swell heights associated with its passage were reported to be 5 to 13 ft, respectively, both moving southeast (report by the Liberian vessel Cape Mandalena; coord: 38° N, 74.4° W; NOAA's Mariners Weather Log, March 1980 Vol. 24, No. 2). By comparison, waves generated by the extratropical cyclone of March 5-8, 1962, reached heights of more than 27 ft (CNA, 1977). Not all high waves, however, are associated with low pressure systems. On November 17, 1977, a high pressure system (1,035 mb) centered at approximately 42° N, 67° W generated easterly winds that, blowing over a long fetch, created higher than normal waves and surf (NOAA's Mariners Weather Log, 1978, Vol. 22, No. 1). This storm resulted in serious beach erosion along the exposed coastline.

The most destructive phenomenon accompanying cyclones are storm surges. Defined as the difference between the observed sea level and the sea level that would have occurred in the absence of the storm, storm surges result from a combination of atmospheric pressure, direct winds, water transport by waves and swell, rainfall, bathymetry, coastline configuration, and the earth's rotation (CNA, 1977). Waves breaking near the shore greatly amplify the storm surge height in the immediate vicinity of the shoreline. The most dangerous storms, in terms of wave generation, are those that pass well offshore.

Icebergs, another destructive phenomenon, rarely occur in this sale region. Bay ice occurs in many bays and inlets along the coast from December to March. This, however, is only a minor inconvenience.

More information on physical oceanography can be found in FEIS OCS Sale No. 49, PP. 98-121.

Over

The proposed Sale No. 111 region is shown in Figure I.A.1. the entire region, surface winds, temperature, visibility, precipitation, hurricanes, and icing potential may present obstacles to OCS oil and gas activities.

The combined effects of surface winds and the Coriolis force play an important role in the movement of pollutants at the sea surface, moving waters to the right of the wind direction in the Northern Hemisphere. Air pollutant transport, however, is determined by surface and upper level wind characteristics. In the mixed layer, transport and sea state are also dependent on surface wind characteristics. Over the western half of the region, the January mean wind vectors are west-northwesterly at approximately 8 to 10 kt; in July, the flow is mostly south-southwesterly at about 4 to 5 kt (Williams and Godshall, 1977). There is a marked increase in the wind speed in the eastern portion of the proposed sale region as well as a shift in the direction of the wind relative to the wind direction in the western half. Table III.A.3 shows mean speed and prevailing direction of average surface winds over the eastern portion. Figure III.A.3-1 shows the western area divided into 15 subareas where wind vectors have been plotted for the January, April, July, and October mean vector winds.

Table III.A.3.

Average Surface Winds in the Eastern Portion of the Proposed Sale Region, by Month, Speed, and Direction (Weather-ship Hotel data)