• Böning, C. W., , F. O. Bryan, , W. R. Holland, , and R. Döscher, 1996: Deep-water formation and meridional overturning in a high resolution model of the North Atlantic. J. Phys. Oceanogr., 26 , 11421164.

    • Search Google Scholar
    • Export Citation
  • Bullister, J. L., , and R. F. Weiss, 1988: Determination of CCl3F and CCl2F2 in seawater and air. Deep-Sea Res., 35 , 839853.

  • Clarke, A., , and J-C. Gascard, 1983: The formation of Labrador Sea Water: Part I: Large scale processes. J. Phys. Oceanogr., 13 , 17641778.

    • Search Google Scholar
    • Export Citation
  • Cunnold, D. M., , P. J. Fraser, , R. F. Weiss, , R. G. Prinn, , P. G. Simmonds, , S. R. Miller, , F. N. Alyea, , and A. J. Crawford, 1994: Global trends and annual releases of CCl3F and CCl2F2 estimated from ALE/GAGE and other measurements from July 1987 to June 1991. J. Geophys. Res., 99 , 11071126.

    • Search Google Scholar
    • Export Citation
  • Curry, R. G., , M. S. McCartney, , and T. M. Joyce, 1998: Oceanic transport of subpolar climate signals to mid-depth subtropical waters. Nature, 391 , 575577.

    • Search Google Scholar
    • Export Citation
  • Davis, R. E., 1998: Preliminary results from directly measuring middepth circulation in the tropical and South Pacific. J. Geophys. Res., 103 , 2461924639.

    • Search Google Scholar
    • Export Citation
  • Delworth, T. L., , and R. J. Greatbatch, 2000: Multidecadal thermohaline circulation variability driven by atmospheric surface flux forcing. J. Climate, 13 , 14811495.

    • Search Google Scholar
    • Export Citation
  • Delworth, T. L., , S. Manabe, , and R. J. Stauffer, . 1993: Interdecadal variations of the thermohaline circulation in a coupled ocean–atmosphere model. J. Climate, 6 , 19932010.

    • Search Google Scholar
    • Export Citation
  • Dickson, R. R., , J. Lazier, , J. Meincke, , P. Rhines, , and J. Swift, 1996: Long term coordinated changes in the convective activity of the North Atlantic. Progress in Oceanography, Vol. 38, Pergamon, 241–295.

    • Search Google Scholar
    • Export Citation
  • Fischer, J., , and F. Schott, 2002: Labrador Sea Water tracked by profiling floats—From the boundary current into the open North Atlantic. J. Phys. Oceanogr, 32 , 573584.

    • Search Google Scholar
    • Export Citation
  • Fleischmann, U., , H. Hildebrandt, , A. Putzka, , and R. Bayer, 2002: Transport of Iceland Scotland Overflow Water from the Iceland Basin to the West European Basin. Deep-Sea Res., in press.

    • Search Google Scholar
    • Export Citation
  • Harvey, J. G., , and A. Theodorou, 1986: The circulation of Norwegian Sea overflow water in the eastern North Atlantic. Oceanol. Acta, 9 , 393402.

    • Search Google Scholar
    • Export Citation
  • Hurrell, J. W., 1995: Decadal trends in the North Atlantic Oscillation: Regional temperatures and precipitation. Science, 269 , 676679.

    • Search Google Scholar
    • Export Citation
  • Körtzinger, A., , M. Rhein, , and L. Mintrop, 1999: Anthropogenic CO2 and CFCs: Man made tracers in unison in the North Atlantic Ocean. Geophys. Res. Lett., 26 , 20652068.

    • Search Google Scholar
    • Export Citation
  • Lazier, J. R. N., 1988: Temperature and salinity changes in the deep Labrador Sea, 1962–1986. Deep-Sea Res., 35 , 12471253.

  • Lilly, J. M., , P. B. Rhines, , M. Visbeck, , R. Davies, , J. Lazier, , F. Schott, , and D. Farmer, 1999: Observing deep convection in the Labrador Sea during winter 1994/95. J. Phys. Oceanogr., 29 , 20652098.

    • Search Google Scholar
    • Export Citation
  • Marsh, R., 2000: Recent variability of the North Atlantic thermohaline circulation inferred from surface heat and freshwater fluxes. J. Climate, 13 , 32393260.

    • Search Google Scholar
    • Export Citation
  • McCartney, M. S., 1992: Recirculating components to the deep boundary current of the northern North Atlantic. Progress in Oceanography, Vol. 29, Pergamon, 283–383.

    • Search Google Scholar
    • Export Citation
  • McCartney, M. S., , and L. D. Talley, 1984: Warm-to-cold conversion in the northern North Atlantic Ocean. J. Phys. Oceanogr., 14 , 922935.

    • Search Google Scholar
    • Export Citation
  • Molinari, R. L., , R. A. Fine, , W. D. Wilson, , R. G. Curry, , J. Abell, , and M. S. McCartney, 1998: The arrival of recently formed Labrador Sea Water in the Deep Western Boundary Current at 26.5°N. Geophys. Res. Lett., 25 , 22492252.

    • Search Google Scholar
    • Export Citation
  • Nurser, A. J. G., , R. Marsh, , and R. G. Williams, 1999: Diagnosing water mass formation from air–sea fluxes and surface mixing. J. Phys. Oceanogr., 29 , 14681487.

    • Search Google Scholar
    • Export Citation
  • Pickart, R. S., 1992: Water mass components of the North Atlantic deep western boundary current. Deep-Sea Res., 9 , 15531572.

  • Price, J. F., and O'Neil-Baringer, 1994: Outflow and deepwater production by marginal seas. Progress in Oceanography, Vol. 33, 161–200.

    • Search Google Scholar
    • Export Citation
  • Rhein, M., 1991: Ventilation rates of the Greenland and Norwegian Seas derived from distributions of the chlorofluoromethanes F11 and F12. Deep-Sea Res., 38 , 485503.

    • Search Google Scholar
    • Export Citation
  • Rhein, M., . 1995: Deep water formation in the Western Mediterranean. J. Geophys. Res., 100 , 69436959.

  • Rhein, M., . 1996: Convection in the Greenland Sea 1982–1993. J. Geophys. Res., 101 , 1818318192.

  • Rossby, H. T., 1996: The North Atlantic Current and surrounding waters: At the crossroads. Rev. Geophys., 34 , 463481.

  • Schmitz, W. J., , and M. S. McCartney, 1993: On the North Atlantic circulation. Rev. Geophys., 31 , 2949.

  • Smethie, W. M., , and J. H. Swift, 1989: The tritium:krypton-85 age of Denmark Strait Overflow waters and Gibbs Fracture Zone Water just south of Denmark Strait. J. Geophys. Res., 94 , 82658275.

    • Search Google Scholar
    • Export Citation
  • Smethie, W. M., , and R. A. Fine, 2001: Rates of North Atlantic Deep Water formation calculated from chlorofluorocarbon inventories. Deep-Sea Res., 48, 189–215.

    • Search Google Scholar
    • Export Citation
  • Smethie, W. M., , R. A. Fine, , A. Putzka, , and E. P. Jones, . 2000: Tracing the flow of North Atlantic Deep Water using chlorofluorocarbons. J. Geophys. Res., 105 , 1429714323.

    • Search Google Scholar
    • Export Citation
  • Speer, K., , and E. Tziperman, 1992: Rates of water mass formation in the North Atlantic Ocean. J. Phys. Oceanogr., 22 , 93104.

  • Swift, J. H., 1984: The circulation of the Denmark Strait and Iceland–Scotland overflow waters in the North Atlantic. Deep-Sea Res., 31 , 13391355.

    • Search Google Scholar
    • Export Citation
  • Sy, A., , M. Rhein, , J. R. N. Lazier, , K. P. Koltermann, , J. Meincke, , A. Putzka, , and M. Bersch, 1997: Surprisingly rapid spreading of newly formed intermediate waters across the North Atlantic Ocean. Nature, 386 , 675679.

    • Search Google Scholar
    • Export Citation
  • Talley, L. D., , and M. S. McCartney, 1982: Distribution and circulation of Labrador Sea Water. J. Phys. Oceanogr., 12 , 11891205.

  • Walker, S. J., , R. F. Weiss, , and P. K. Salameh, 2000: Reconstructed histories of the annual mean atmospheric mole fractions of the halocarbons CFC-11, CFC-12, CFC-113 and carbon tetrachloride. J. Geophys. Res., 105 , 1426514296.

    • Search Google Scholar
    • Export Citation
  • Wallace, D. W. R., , and J. R. N. Lazier, 1988: Anthropogenic chlorofluoromethanes in newly formed Labrador Sea Water. Nature, 332 , 6163.

    • Search Google Scholar
    • Export Citation
  • Wood, R. A., , A. B. Keen, , J. F. B. Mitchell, , and J. M. Gregory, 1999: Changing spatial structure of the thermohaline circulation in response to atmospheric CO2 forcing in a climate model. Nature, 399 , 572575.

    • Search Google Scholar
    • Export Citation
  • Worthington, L. V., 1976: On the North Atlantic Circulation. The John Hopkins Oceanography Studies, No. 6, The Johns Hopkins University Press, 110 pp.

    • Search Google Scholar
    • Export Citation
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Labrador Sea Water: Pathways, CFC Inventory, and Formation Rates

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  • * Institut für Meereskunde Kiel, Kiel, Germany
  • | + Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York
  • | # Southampton Oceanography Centre, Southampton, United Kingdom
  • | @ Scripps Institution of Oceanography, La Jolla, California
  • | 5 Institut für Umweltpbysik, Universität Bremen, Bremen, Germany
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Abstract

In 1997, a unique hydrographic and chlorofluorocarbon (CFC: component CFC-11) dataset was obtained in the subpolar North Atlantic. To estimate the synopticity of the 1997 data, the recent temporal evolution of the CFC and Labrador Sea Water (LSW) thickness fields are examined. In the western Atlantic north of 50°N, the LSW thickness decreased considerably from 1994–97, while the mean CFC concentrations did not change much. South of 50°N and in the eastern Atlantic, the CFC concentration increased with little or no change in the LSW thickness. On shorter timescales, local anomalies due to the presence of eddies are observed, but for space scales larger than the eddies the dataset can be treated as being synoptic over the 1997 observation period.

The spreading of LSW in the subpolar North Atlantic is described in detail using gridded CFC and LSW thickness fields combined with Profiling Autonomous Lagrangian Circulation Explorer (PALACE) float trajectories. The gridded fields are also used to calculate the CFC-11 inventory in the LSW from 40° to 65°N, and from 10° to 60°W. In total, 2300 ± 250 tons of CFC-11 (equivalent to 16.6 million moles) were brought into the LSW by deep convection. In 1997, 28% of the inventory was still found in the Labrador Sea west of 45°W and 31% of the inventory was located in the eastern Atlantic.

The CFC inventory in the LSW was used to estimate the lower limits of LSW formation rates. At a constant formation rate, a value of 4.4–5.6 Sv (Sv ≡ 106 m3 s−1) is obtained. If the denser modes of LSW are ventilated only in periods with intense convection, the minimum formation rate of LSW in 1988–94 is 8.1–10.8 Sv, and 1.8–2.4 Sv in 1995–97.

Current affiliation: Institut für Umweltphysik, Universität Bremen, Bremen, Germany

Current affiliation: School of Oceanography, University of Washington, Seattle, Washington

Corresponding author address: Dr. Monika Rhein, Universität Bremen, FB1, Institut für Umweltphysik, Abt. Ozeanographie, Kufsteiner Strasse, Geb. NW1, 28359 Bremen, Germany. Email: mrhein@physik.uni-bremen.de

Abstract

In 1997, a unique hydrographic and chlorofluorocarbon (CFC: component CFC-11) dataset was obtained in the subpolar North Atlantic. To estimate the synopticity of the 1997 data, the recent temporal evolution of the CFC and Labrador Sea Water (LSW) thickness fields are examined. In the western Atlantic north of 50°N, the LSW thickness decreased considerably from 1994–97, while the mean CFC concentrations did not change much. South of 50°N and in the eastern Atlantic, the CFC concentration increased with little or no change in the LSW thickness. On shorter timescales, local anomalies due to the presence of eddies are observed, but for space scales larger than the eddies the dataset can be treated as being synoptic over the 1997 observation period.

The spreading of LSW in the subpolar North Atlantic is described in detail using gridded CFC and LSW thickness fields combined with Profiling Autonomous Lagrangian Circulation Explorer (PALACE) float trajectories. The gridded fields are also used to calculate the CFC-11 inventory in the LSW from 40° to 65°N, and from 10° to 60°W. In total, 2300 ± 250 tons of CFC-11 (equivalent to 16.6 million moles) were brought into the LSW by deep convection. In 1997, 28% of the inventory was still found in the Labrador Sea west of 45°W and 31% of the inventory was located in the eastern Atlantic.

The CFC inventory in the LSW was used to estimate the lower limits of LSW formation rates. At a constant formation rate, a value of 4.4–5.6 Sv (Sv ≡ 106 m3 s−1) is obtained. If the denser modes of LSW are ventilated only in periods with intense convection, the minimum formation rate of LSW in 1988–94 is 8.1–10.8 Sv, and 1.8–2.4 Sv in 1995–97.

Current affiliation: Institut für Umweltphysik, Universität Bremen, Bremen, Germany

Current affiliation: School of Oceanography, University of Washington, Seattle, Washington

Corresponding author address: Dr. Monika Rhein, Universität Bremen, FB1, Institut für Umweltphysik, Abt. Ozeanographie, Kufsteiner Strasse, Geb. NW1, 28359 Bremen, Germany. Email: mrhein@physik.uni-bremen.de

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