No abstract

Objectively analyzed surface hydrographic fields and NCEP-NCAR reanalysis fluxes are used to estimate water mass transformation and formation rates in the Labrador Sea, focusing on Labrador Sea Water (LSW). The authors estimate a mean long-term transformation of between 2.1 Ϯ 0.2 and 3.9 Ϯ 0.3 Sv (Sv ϵ 10 6 m 3 s Ϫ1 ) over the years 1960-99 to water with densities greater than ϭ 27.65 kg m Ϫ3 , depending on the correction used for the latent and sensible heat fluxes. Mean long-term formation rates are found between 0.9 Ϯ 0.2 and 1.7 Ϯ 0.3 Sv for ϭ 27.675 Ϫ 27.725 kg m Ϫ3 and 1.2 Ϯ 0.2 and 2.0 Ϯ 0.3 Sv for Ͼ 27.725 kg m Ϫ3 . There is tremendous variability associated with these formation rates with years of strong water formation (5.7-6.6 Ϯ 0.5-0.7 or 9.5-10.8 Ϯ 0.7-1.1 Sv) mixed with years of little or no formation in the given density ranges. The North Atlantic Oscillation (NAO) is linked (correlation coefficient of 0.45, significant at the 99% level) with the overall formation rate for Ͼ 27.625 kg m Ϫ3 . The observed long-term increase in net precipitation over the Labrador Sea does not seem to have had any significant effect on LSW, potentially reducing LSW transformation rates by 0.1 Sv. A reduction in surface salinity leads to formation occurring at a reduced density, but with little change in the amount of water transformed.