Offshore currents were also examined by Vermersch and coworkers (1979). No 

 surface currents were observed but at 100 feet (33 m) the currents were 

 consistent with Bigelow's gyre (figure 4-8). The 100 feet (33 m) mean flow 

 approximately parallels the bathymetric contours to the southwest and with 

 depth the currents veer onshore. The authors note that these currents have 

 only a very weak coherence with the local winds and they suggest that possibly 

 the rough bottom topography interacts with the alongshore flow to produce 

 eddies . 



The major features of the nontidal circulation along the coast are summarized 

 by Graham (1970b; figure 4-10 and table 4-4). The westward surface flow is 

 more pronounced west of the Mt . Desert region (region 5) and more variable to 

 the east, especially in Grand Manan Channel (region 6), where it often 

 reverses. In the area just to the east of Penobscot Bay (region 4), the 

 surface drift is often offshore. Along the bottom the nontidal flow is 

 generally inshore, indicating that upwelling is the predominant feature of the 

 coastal circulation. This representation is extremely general. In many 

 areas, particularly the region between Grand Manan Island and Penobscot Bay, 

 very little is known about the mean circulation and almost nothing about the 

 short-term variability. 



Except for the results of Hartwell (1976) in New Hampshire, and Naval 

 Underwater Systems Center (NUSC; 1979) in Casco Bay (region 1), direct current 

 measurements in the coastal area of the Gulf of Maine are largely lacking. 

 Data from a current meter array located approximately 4.2 miles (7 km) 

 northeast of the Portland Buoy are being analyzed. These data will provide 

 additional local information on both the tidal and nontidal flow regimes. 



Nearshore data (Naval Underwater Systems Center 1979, and Hartwell 1976) 

 indicate that nontidal currents are correlated with meteorological events. 

 Data from New Hampshire waters (south of the characterization area; Hartwell 

 1976) show summer currents to be weaker and more dominated by tidal currents 

 than winter currents. In winter, currents quickly respond to winds associated 

 with storms. If low pressure systems pass to the south of an area southward 

 flows are produced and those passing to the north produce northward flows. In 

 spring and fall this bimodal tendency decreases and increases respectively. 



In summary, although general trends of currents in Maine's coastal waters can 

 be surmised, small-scale variability is considerable. The many factors that 

 affect coastal currents make predicting water movement and the accompanying 

 dispersal of nutrients, phytoplankton, and pollutants (e.g., oil) difficult. 

 Conditions (e.g., winds, and stage of tide) prevailing at a particular point 

 in time are critical in determining where and how fast a water mass will move. 



Climate 



Meteorological factors influence both abiotic factors (e.g., hydrography and 

 geology) and the biota. 



Wind. Winds play an important role in moving surface waters. The effect 

 depends on strength, duration, and fetch. The predominant winds in coastal 

 Maine are from the southwest in summer and from the northwest in winter (see 

 "Climate," page 2-9in chapter 2). Splash and surge from waves produced by 

 winds provide more moisture to the intertidal zone than a calm sea provides. 



4-25 



10-80 



