Sack Lunch Seminar (SLS)

Variability in the Labrador Sea Water within the Deep Western Boundary
Current
southeast of Cape Cod






Water properties measured by the Line W mooring array southeast of Cape Cod
document a large character shift during the period of November 2001 to April
2008. The vertical structure of the variability at Line W is characterized by
alternating layers of colder (warmer) and fresher (more saline) anomalies
located at the depths where Upper Labrador Sea Water (ULSW), Classical Labrador
Sea Water (CLSW) and Overflow Water (OW) are typically found. During the
observation period, the PPV minimum (in the anomaly field) originally found at
1500m, migrated to a shallower position (lower density), centered at 700m. The
structure of these anomalies is consistent with observations within the
Labrador Sea, and their transit time to the Line W site agrees well with
tracer-derived advective times. In that context, the observed water properties
at Line W in the early 2000s reflected the intense deep convection that
occurred in the Labrador Sea in the mid 90s, with less intense convection
subsequently affecting lighter isopycnals.
A fraction of the total variability in the velocity field at Line W is
correlated with changes in the water mass properties and indicates a gradual
acceleration of the southwestward flow, with a corresponding increase in Deep
Western Boundary Current (DWBC) transport.