(Woods Hole Oceanographic Institution, 1980-12)
McCartney, Michael S.; Worthington, L. Valentine; Raymer, Mary E.
A hydrographic section made in July 1977 from the research vessel KNORR revealed a
large-scale meridional distortion of the normal water mass distributions at 55W in the North
Atlantic. Cells of pure Labrador Sea Water were found within both the Gulf Stream and the
westward recirculation of the gyre. A large cell of Mediterranean Water was found in the Slope
Water, in contact with a cell of Subarctic Intermediate Water. Water at 11°C to 13°C within
both the Gulf Stream and the Slope Water was anomalously saline. Throughout the Slope
Water, Gulf Stream, and northern Sargasso Sea there was very little standard Western North
Atlantic Water in the temperature ranges 3.4° to 9.0°C and 11° to 13°C. It is suggested that
these meridional distortions are due in part to an increase in the amount of rotation of the
horizontal velocity vector with depth during 1977 that was observed with current meters in the
northern Sargasso Sea. An increase in the westward return flow strength may also have contributed.
The ultimate cause of the anomalous property distributions and currents may be
changes in the production rate and strength of the source waters for North Atlantic Deep Water
and western North Atlantic Water such as Labrador Sea Water, Mediterranean Water, and
Eighteen Degree Water. The first and the last are known to have undergone convective formation
events, in March 1976, and March 1977, respectively, in the period preceding the 1977
survey. The July 1977 section shows evidence of the recirculation of the new convectively
formed Eighteen Degree Water.
