Tidal asymmetry

Tidal asymmetry could also occur if the selected creek cross section was not situated within a closed creek network, which would mean that a parcel of water could exit from a different place to where it entered. This could occur if two creek systems were connected, or could exchange water during an overtopping tide. The proportion of water entering and leaving the marsh from the two mouths would depend on wind direction and tidal flow patterns. 

Boon, J. (Ill) (1975) Tidal discharge asymmetry in a saltmarsh drainage system. Limnology and Oceanography 20, 71-80. 

Even given Europa s orbital eccentricity e, the rotation might be synchronous if a non-spherically symmetric, frozen-in density distribution (like that of the Earth s Moon) were locked to the direction of Jupiter. Given that Europa is substantially heated by tidal friction, it may not be able to support such a frozen-in asymmetry. It is also conceivable that the silicate interior is locked to the direction of Jupiter by a mass asymmetry, while the ice crust, uncoupled from the silicate by an intervening liquid water layer, rotates non-synchronously due to the tidal torque. 

However, even a completely solid Europa would rotate non-synchronously as long as mass asymmetries are small enough. Non-synchronous rotation does not in itself imply the existence of an ocean. However, both the existence of an ocean and Non-synchronous rotation are made possible by the substantial tidal heating. 

E. E. Carr and N. C. Kraus, Morphologic asymmetries at entrances to tidal inlets, ERDC/CHL CHETN-IV-33, U.S. Army Eng. Res. and Develop. Center, Vicksburg, MS (2001), http //chl.wes.army.mil/library/publications/chetn. 

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