The circulation features include the West Greenland Current and the Labrador Current. The Labrador Sea is part of the pathway through which the low salinity outflows of the Arctic Ocean move southward and downward toward denser surfaces. This low salinity can follow two pathways: mixing across fronts and subsequent incorporation into the subpolar and eventually the subtropical gyre circulation; or the water can move offshore into the Labrador and Irminger Seas and be mixed down the following winter as Irminger Sea Water or LSW.
Observations indicate considerable fluctuations of salinity in the upper waters on both a seasonal and interannual basis, which renders it difficult to create an average picture of the hydrography from historical data (of which there is much in this region). Climatologically, this is a region where the first effects of atmospheric warming induced by CO2 or other greenhouse gases might be seen. Milder winters would lead to less overturning and accumulation of low salinity waters in the upper layers, an affect which would be exacerbated by increased glacial and polar ice melt as well as increased high latitude precipitation. This could very well turn off the production of LSW with possible global consequences. See Tomczak and Godfrey (1994) and U. S. Science Steering Committee for WOCE (1986).
LSW mixes with ABW and eventually becomes part of NADW, although the abovementioned variability is not wholly passed on to NADW. The ABW/LSW mixture recirculates around the Labrador Sea an estimated 2 to 3 times over 12 to 18 months, a process which serves to smooth out interannual fluctuations and results in NADW receiving water with about half the original variation in magnitude of LSW. See Tomczak and Godfrey (1994).
where 
are longitude and latitude with corresponding
velocity components (u,v), 
the ocean surface elevation,
the tide-generating potential, D the variable depth of
the ocean, a the earth's radius, g the gravitational acceleration
at the earth's surface, and 
the earth's angular rate of
rotation.
These equations were eventually found to not be uniformly valid, a problem that was eventually fixed by relaxing the assumption of homogeneous fluid to allow stratification and developing a similar equation set called the long wave equations. Both sets are used to investigate such long ocean waves as Rossby waves, Poincare waves, Kelvin waves and the like, although these are more commonly and easily studied using an equation set written in cartesian coordinates on a beta plane or an f-plane. For example, the LTEs simplified for long waves in a uniformly rotating flat-bottomed ocean, i.e. an f-plane, are
where 
, equal to 
, is the
Coriolis parameter.
See Lamb (1932), sect. 213-221 and
Hendershott (1981).
for condensation
or evaporation,
for fusion or
melting, and
for deposition
or sublimation, with the sign depending on the direction of the
change.