The arrival of a «new» Labrador Sea Water signal in the tropical Atlantic in 1996

Abstract

We describe results inferred from the tracking, in the tropical Atlantic, of CFC signals linked to the intensification of convection processes in the Labrador Sea since 1988. CFC and hydrology series (1993-1997) off French Guiana (7°N) have been investigated in order to analyse LSW characteristics and their variability. A dramatic increase of the CFC concentrations below 2000 m at the level of the classical LSW has been observed in April 1996. Using CFC and salinity data, the comparison of the (1993-1997) series at 7°N with a (1989-1999) series at 35°W indicates that the sporadic 1996 event has been followed in the equatorial Atlantic in the late 90s by the arrival of a more continuous newly ventilated LSW flow. This study evaluates a transit time from the Labrador basin to the tropics of less than one decade, in agreement with direct current measurements.