We have learned that the cross-estuary tilt of the pycno- 
cline resulting from the rotation of the earth can be upset by 
the wind. A cross-sectional view looking up the Chesapeake Bay 
at Mid-Bay shows a higher salinity water along the eastern 
shore. A cross estuary wind can not only reverse this slope, 
but also drive upwelling along the side. 
Mixing: The crux of the ocean circulation problem has for a 
long time been with the small-scale motions of the ocean we call 
turbulence and which causes mixing. We don't understand it very 
well, but we try hard, for the rewards are a more accurate de¬ 
scription of the larger scale circulation processes. Mixing pro 
cesses in the estuary were traditionally thought to be moving 
back and forth over the bottom with the tidal currents. We see 
it as a balance between the horizontal motions tending to pro¬ 
duce what's called buoyancy flux versus the act of vertical mo¬ 
tions to destroy that stratification. 
If we apply bottom-generated turbulence and turbulence 
generated by the wind at the surface to the salinity versus the 
depth profile, then this smooth increase in salt with depth 
would change. Classical entrainment theory would predict that 
this smooth change would become abrupt. It turns out that the 
Bay looks more like the smooth profile, even with winds stirring 
the upper layers. We are forced therefore to examine the mixing 
processes in more detail. Internal waves and shear instability 
mechanisms are throught to be important here, but the precise 
mechanisms are still unknown. 
I list in Table 1 a category called "topographically induced 
circulation" that comprises many flow processes. If you are a 
kayaker or canoeist or a stream fisherman, you would laugh at 
what we consider discoveries in this area -- superimposed on the 
steady flow of the estuary are many eddies and jets and regions 
of high and low currents. This LANDSAT satellite image shows 
the dendritic nature of the Chesapeake Bay's geometry. The 
channel curvature and the complex side boundaries generate many 
local flow features that influence the transport of water and 
waterborne materials in the estuary. An intense array of 
instruments such as this one deployed in the Potomac River is 
necessary to examine such flow features. With this array we 
revealed small-scale jets, eddies, and both coupled and 
independent flows in the upper and lower layers. 
Tributary — main stem interaction: This area of research 
is of particular interest at the moment. We are finding that 
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