• Aoki, S., , M. Harimaya, , H. Mitsudera, , H. Sasaki, , and Y. Sasai, 2007: Formation regions of Subantarctic Mode Water detected by OFES and Argo profiling floats. Geophys. Res. Lett., 34, L10606, doi:10.1029/2007GL029828.

    • Search Google Scholar
    • Export Citation
  • Bacon, S., 2002: RRS James Clark Ross cruise 67, 19 Nov–17 Dec 2001. Drake Passage repeat hydrography: WOCE southern repeat section 1b—Burdwood Bank to Elephant Island. Southampton Oceanography Centre Cruise Rep. 38, 118 pp.

  • Bacon, S., 2003: RRS James Clark Ross cruise 81, 18 Dec 2002–02 Jan 2003. Drake Passage repeat hydrography: WOCE southern repeat section 1b—Elephant Island to Burdwood Bank. Southampton Oceanography Centre Cruise Rep. 43, 86 pp.

  • Bacon, S., , and S. Cunningham, 2005: Drake Passage summary report: Cruises on RRS “James Clark Ross,” 1993–2000. Drake Passage repeat hydrography: WOCE southern repeat section 1b—Elephant Island to Burdwood Bank. Southampton Oceanography Centre Cruise Rep. 44, 151 pp.

  • Baines, P. G., , and K. Fraedrich, 1989: Topographic effects on the mean tropospheric flow patterns around Antarctica. J. Atmos. Sci., 46, 34013415.

    • Search Google Scholar
    • Export Citation
  • Bindoff, N. L., , and J. A. Church, 1992: Warming of the water column in the southwest Pacific Ocean. Nature, 357, 5962, doi:10.1038/357059a0.

    • Search Google Scholar
    • Export Citation
  • Bindoff, N. L., , and T. J. McDougall, 2000: Decadal changes along an Indian Ocean section at 32°S and their interpretation. J. Phys. Oceanogr., 30, 12071222.

    • Search Google Scholar
    • Export Citation
  • Bindoff, N. L., and Coauthors, 2007: Observations: Oceanic climate change and sea level. Climate Change 2007: The Physical Science Basis, S. Solomon et al., Eds., Cambridge University Press, 385–432.

  • Biuw, M., and Coauthors, 2007: Variations in behavior and condition of a Southern Ocean top predator in relation to in situ oceanographic conditions. Proc. Natl. Acad. Sci. USA, 104, 13 70513 710, doi:10.1073/pnas.0701121104.

    • Search Google Scholar
    • Export Citation
  • Boehme, L., , M. P. Meredith, , S. E. Thorpe, , M. Biuw, , and M. Fedak, 2008a: Antarctic Circumpolar Current frontal system in the South Atlantic: Monitoring using merged Argo and animal-borne sensor data. J. Geophys. Res., 113, C09012, doi:10.1029/2007JC004647.

    • Search Google Scholar
    • Export Citation
  • Boehme, L., , S. Thorpe, , M. Biuw, , M. Fedak, , and M. Meredith, 2008b: Monitoring Drake Passage with elephant seals: Frontal structures and snapshots of transport. Limnol. Oceanogr., 53, 23502360, doi:10.4319/lo.2008.53.5_part_2.2350.

    • Search Google Scholar
    • Export Citation
  • Boehme, L., , P. Lovell, , M. Biuw, , F. Roquet, , J. Nicholson, , S. E. Thorpe, , M. P. Meredith, , and M. Fedak, 2009: Technical note: Animal-borne CTD-satellite relay data loggers for real-time oceanographic data collection. Ocean Sci., 5, 685695.

    • Search Google Scholar
    • Export Citation
  • Böning, C. W., , A. Dispert, , M. Visbeck, , S. R. Rintoul, , and F. U. Schwarzkopf, 2008: The response of the Antarctic Circumpolar Current to recent climate change. Nat. Geosci., 1, 864–869, doi:10.1038/ngeo362.

    • Search Google Scholar
    • Export Citation
  • Boyer, T. P., and Coauthors, 2009: World Ocean Database 2009. NOAA Atlas NESDIS 66, 217 pp.

  • Bromwich, D. H., , and R. L. Fogt, 2004: Strong trends in the skill of the ERA-40 and NCEP–NCAR reanalyses in the high and midlatitudes of the Southern Hemisphere, 1958–2001. J. Climate, 17, 46034619.

    • Search Google Scholar
    • Export Citation
  • Bryden, H., , E. McDonagh, , and B. King, 2003: Changes in ocean water mass properties: Oscillations or trends? Science, 300, 2086–2088, doi:10.1126/science.1083980.

    • Search Google Scholar
    • Export Citation
  • Carleton, A. M., 2003: Atmospheric teleconnections involving the Southern Ocean. J. Geophys. Res., 108, 8080, doi:10.1029/2000JC000379.

  • Carval, T., and Coauthors, 2008: User's manual: Version 2.1. Argo Data Management Tech. Rep. ar-um-02-01, 61 pp. [Available online at http://w3.jcommops.org/FTPRoot/Argo/Doc/argo-dm-user-manual.pdf.]

  • Cavalieri, D., , C. Parkinson, , P. Gloersen, , and H. J. Zwally, cited 2008: Sea ice concentrations from Nimbus-7 SMMR and DMSP SSM/I passive microwave data [1978–2007]. National Snow and Ice Data Center. [Available online at http://nsidc.org/data/nsidc-0051.html.]

  • Charrassin, J.-B., and Coauthors, 2008: Southern Ocean frontal structure and sea-ice formation rates revealed by elephant seals. Proc. Natl. Acad. Sci. USA, 105, 11 63411 639, doi:10.1073/pnas.0800790105.

    • Search Google Scholar
    • Export Citation
  • Chen, B., , S. R. Smith, , and D. H. Bromwich, 1996: Evolution of the tropospheric split jet over the South Pacific Ocean during the 1986–89 ENSO cycle. Mon. Wea. Rev., 124, 17111731.

    • Search Google Scholar
    • Export Citation
  • Church, J. A., , J. S. Godfrey, , D. R. Jackett, , and T. J. McDougall, 1991: A model of sea level rise caused by ocean thermal expansion. J. Climate, 4, 438456.

    • Search Google Scholar
    • Export Citation
  • Ciasto, L. M., , and M. H. England, 2011: Observed ENSO teleconnections to Southern Ocean SST anomalies diagnosed from a surface mixed layer heat budget. Geophys. Res. Lett., 38, L09701, doi:10.1029/2011GL046895.

    • Search Google Scholar
    • Export Citation
  • Close, S. E., 2011: Southern Ocean water mass variability and its causes. Ph.D. thesis, University of Southampton, 244 pp.

  • Close, S. E., , and A. C. Naveira Garabato, 2012: Baroclinic adjustment in Drake Passage driven by tropical Pacific forcing. Geophys. Res. Lett., 39, L19610, doi:10.1029/2012GL053402.

    • Search Google Scholar
    • Export Citation
  • Cunningham, S., 2001: RRS James Clark Ross cruise JR55, 21 Nov-14 Dec 2000. Drake Passage repeat hydrography: WOCE southern section 1b—Burdwood Bank to Elephant Island. Southampton Oceanography Centre Cruise Rep. 35, 75 pp.

  • Curry, R., , B. Dickson, , and I. Yashayaev, 2003: A change in the freshwater balance of the Atlantic Ocean over the past four decades. Nature, 426, 826829, doi:10.1038/nature02206.

    • Search Google Scholar
    • Export Citation
  • de Boyer Montégut, C., , G. Madec, , A. S. Fischer, , A. Lazar, , and D. Iudicone, 2004: Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology. J. Geophys. Res., 109, C12003, doi:10.1029/2004JC002378.

    • Search Google Scholar
    • Export Citation
  • Dee, D. P., and Coauthors, 2011: The ERA-Interim reanalysis: Configuration and performance of the data assimilation system. Quart. J. Roy. Meteor. Soc., 137, 553597, doi:10.1002/qj.828.

    • Search Google Scholar
    • Export Citation
  • Durack, P. J., , and S. E. Wijffels, 2010: Fifty-year trends in global ocean salinities and their relationship to broad-scale warming. J. Climate, 23, 43424362.

    • Search Google Scholar
    • Export Citation
  • Durack, P. J., , S. E. Wijffels, , and R. J. Matear, 2012: Ocean salinities reveal strong global water cycle intensification during 1950 to 2000. Science, 336, 455458, doi:10.1126/science.1212222.

    • Search Google Scholar
    • Export Citation
  • Fogt, R. L., , D. H. Bromwich, , and K. M. Hines, 2011: Understanding the SAM influence on the South Pacific ENSO teleconnection. Climate Dyn., 36, 15551576, doi:10.1007/s00382-010-0905-0.

    • Search Google Scholar
    • Export Citation
  • Ganachaud, A., , and C. Wunsch, 2000: Improved estimates of global ocean circulation, heat transport and mixing from hydrographic data. Nature, 408, 453457, doi:10.1038/35044048.

    • Search Google Scholar
    • Export Citation
  • Gille, S. T., 2002: Warming of the Southern Ocean since the 1950s. Science, 295, 12751277, doi:10.1126/science.1065863.

  • Gille, S. T., 2008: Decadal-scale temperature trends in the Southern Hemisphere ocean. J. Climate, 21, 47494765.

  • Gough, A. J., , A. R. Mahoney, , P. J. Langhorne, , M. J. M. Williams, , and T. G. Haskell, 2012: Sea ice salinity and structure: A winter time series of salinity and its distribution. J. Geophys. Res., 117, C03008, doi:10.1029/2011JC007527.

    • Search Google Scholar
    • Export Citation
  • Hanawa, K., , and L. Talley, 2001: Mode waters. Ocean Circulation and Climate: Observing and Modelling the Global Ocean, G. Siedler and J. Church, Eds., Academic Press, 373–386.

  • Harangozo, S. A., 2006: Atmospheric circulation impacts on winter maximum sea ice extent in the west Antarctic Peninsula region (1979–2001). Geophys. Res. Lett., 33, L02502, doi:10.1029/2005GL024978.

    • Search Google Scholar
    • Export Citation
  • Hawker, E., , B. King, , and M. Sparrow, 2005: RRS James Clark Ross cruise 94, 01 Dec–15 Dec 2003. Drake Passage repeat hydrography: WOCE southern repeat section 1b—Burdwood Bank to Elephant Island. Southampton Oceanography Centre Cruise Rep. 55, 56 pp.

  • Herraiz-Borreguero, L., , and S. R. Rintoul, 2010: Subantarctic Mode Water variability influenced by mesoscale eddies south of Tasmania. J. Geophys. Res., 115, C04004, doi:10.1029/2008JC005146.

    • Search Google Scholar
    • Export Citation
  • Herraiz-Borreguero, L., , and S. R. Rintoul, 2011: Subantarctic mode water: Distribution and circulation. Ocean Dyn., 61, 103126, doi:10.1007/s10236-010-0352-9.

    • Search Google Scholar
    • Export Citation
  • Hines, K. M., , D. H. Bromwich, , and G. J. Marshall, 2000: Artificial surface pressure trends in the NCEP–NCAR reanalysis over the Southern Ocean and Antarctica. J. Climate, 13, 39403952.

    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., , and A. H. Orsi, 1997: Southwest Pacific Ocean water-mass changes between 1968/69 and 1990/91. J. Climate, 10, 306316.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77, 437471.

  • King, B., , E. Firing, , and T. M. Joyce, 2001: Shipboard observations during WOCE. Ocean Circulation and Climate: Observing and Modelling the Global Ocean, G. Siedler, Ed., Academic Press, 99–122.

  • Lefebvre, W., , H. Goosse, , R. Timmermann, , and T. Fichefet, 2004: Influence of the southern annular mode on the sea ice–ocean system. J. Geophys. Res., 109, C09005, doi:10.1029/2004JC002403.

    • Search Google Scholar
    • Export Citation
  • Levitus, S., , J. I. Antonov, , T. P. Boyer, , and C. Stephens, 2000: Warming of the World Ocean. Science, 287, 22252229, doi:10.1126/science.287.5461.2225.

    • Search Google Scholar
    • Export Citation
  • Levitus, S., , J. I. Antonov, , T. P. Boyer, , R. A. Locarnini, , H. E. Garcia, , and A. V. Mishonov, 2009: Global ocean heat content 1955–2008 in light of recently revealed instrumentation problems. Geophys. Res. Lett., 36, L07608, doi:10.1029/2008GL037155.

    • Search Google Scholar
    • Export Citation
  • Lumpkin, R., , and K. Speer, 2007: Global ocean meridional overturning. J. Phys. Oceanogr., 37, 25502562.

  • Marshall, G. J., 2003: Trends in the southern annular mode from observations and reanalyses. J. Climate, 16, 41344143.

  • McCartney, M. S., 1977: Subantarctic Mode Water. A Voyage of Discovery: George Deacon 70th Anniversary Volume, M. V. Angel, Ed., Pergamon Press, 103–119.

  • McCartney, M. S., 1982: The subtropical recirculation of mode waters. J. Mar. Res., 40 (Suppl.), 427464.

  • McDonagh, E. L., 2009: RRS James Cook cruise JC031, 03 Feb-03 Mar 2009. Hydrographic sections of Drake Passage. National Oceanography Centre, Southampton Cruise Rep. 39, 170 pp.

  • McDonagh, E. L., , H. L. Bryden, , B. A. King, , R. J. Sanders, , S. A. Cunningham, , and R. Marsh, 2005: Decadal changes in the south Indian Ocean thermocline. J. Climate, 18, 15751590.

    • Search Google Scholar
    • Export Citation
  • Meredith, M. P., , K. E. Grose, , E. L. McDonagh, , K. J. Heywood, , R. D. Frew, , and P. F. Dennis, 1999: Distribution of oxygen isotopes in the water masses of Drake Passage and the South Atlantic. J. Geophys. Res., 104 (C9), 20 94920 946.

    • Search Google Scholar
    • Export Citation
  • Meredith, M. P., , E. J. Murphy, , E. J. Hawker, , J. C. King, , and M. I. Wallace, 2008: On the interannual variability of ocean temperatures around south Georgia, Southern Ocean: Forcing by El Niño/Southern Oscillation and the southern annular mode. Deep-Sea Res. II, 55, 20072022, doi:10.1016/j.dsr2.2008.05.020.

    • Search Google Scholar
    • Export Citation
  • Naveira Garabato, A. C., , H. Leach, , J. T. Allen, , R. T. Pollard, , and V. H. Strass, 2001: Mesoscale subduction at the Antarctic Polar Front driven by baroclinic instability. J. Phys. Oceanogr., 31, 20872107.

    • Search Google Scholar
    • Export Citation
  • Naveira Garabato, A. C., , L. Jullion, , D. P. Stevens, , K. J. Heywood, , and B. A. King, 2009: Variability of Subantarctic Mode Water and Antarctic Intermediate Water in the Drake Passage during the late-twentieth and early-twenty-first centuries. J. Climate, 22, 36613688.

    • Search Google Scholar
    • Export Citation
  • Quartly, G., 2010: RRS James Clark Ross cruise 194, 12–23 Dec 2008. Drake Passage repeat hydrography: WOCE southern repeat section 1b—Burdwood Bank to Elephant Island. National Oceanography Centre, Southampton Cruise Rep. 54, 46 pp.

  • Quartly, G., , and H. Venables, 2010: RRS James Clark Ross cruise 193, 29 Nov–08 Dec 2007. Drake Passage repeat hydrography: WOCE southern repeat section 1b—Burdwood Bank to Elephant Island. National Oceanography Centre, Southampton Cruise Rep. 26, 75 pp.

  • Rintoul, S. R., , and M. H. England, 2002: Ekman transport dominates local air–sea fluxes in driving variability of Subantarctic Mode Water. J. Phys. Oceanogr., 32, 13081321.

    • Search Google Scholar
    • Export Citation
  • Sabine, C. L., and Coauthors, 2004: The oceanic sink for anthropogenic CO2. Science, 305, 367–371, doi:10.1126/science.1097403.

  • Saenko, O. A., , and A. J. Weaver, 2001: Importance of wind-driven sea ice motion for the formation of Antarctic Intermediate Water in a global climate model. Geophys. Res. Lett., 28, 41474150.

    • Search Google Scholar
    • Export Citation
  • Sallée, J.-B., , N. Wienders, , K. Speer, , and R. Morrow, 2006: Formation of Subantarctic Mode Water in the southeastern Indian Ocean. Ocean Dyn., 56, 525542, doi:10.1007/s10236-005-0054-x.

    • Search Google Scholar
    • Export Citation
  • Sallée, J.-B., , K. Speer, , S. Rintoul, , and S. Wijffels, 2010: Southern Ocean thermocline ventilation. J. Phys. Oceanogr., 40, 509529.

  • Santoso, A., , and M. H. England, 2004: Antarctic Intermediate Water circulation and variability in a coupled climate model. J. Phys. Oceanogr., 34, 21602179.

    • Search Google Scholar
    • Export Citation
  • Sarmiento, J. L., , N. Gruber, , M. A. Brzezinski, , and J. P. Dunne, 2004: High-latitude controls of thermocline nutrients and low latitude biological productivity. Nature, 427, 5660, doi:10.1038/nature02127.

    • Search Google Scholar
    • Export Citation
  • Schneider, W., , M. Fukasawa, , H. Uchida, , T. Kawano, , I. Kaneko, , and R. Fuenzalida, 2005: Observed property changes in eastern South Pacific Antarctic Intermediate Water. Geophys. Res. Lett., 32, L14602, doi:10.1029/2005GL022801.

    • Search Google Scholar
    • Export Citation
  • Simmonds, I., , and J. C. King, 2004: Global and hemispheric climate variations affecting the Southern Ocean. Antarct. Sci., 16, 401413, doi:10.1017/S0954102004002226.

    • Search Google Scholar
    • Export Citation
  • Sloyan, B. M., , and S. R. Rintoul, 2001: The Southern Ocean limb of the global deep overturning circulation. J. Phys. Oceanogr., 31, 143173.

    • Search Google Scholar
    • Export Citation
  • Smith, C. A., , and P. D. Sardeshmukh, 2000: The effect of ENSO on the intraseasonal variance of surface temperatures in winter. Int. J. Climatol., 20, 15431557.

    • Search Google Scholar
    • Export Citation
  • Sokolov, S., , and S. R. Rintoul, 2002: Structure of Southern Ocean fronts at 140°E. J. Mar. Syst., 37, 151184, doi:10.1016/S0924-7963(02)00200-2.

    • Search Google Scholar
    • Export Citation
  • Sokolov, S., , and S. R. Rintoul, 2009: Circumpolar structure and distribution of the Antarctic Circumpolar Current fronts: 2. Variability and relationship to sea surface height. J. Geophys. Res., 114, C11019, doi:10.1029/2008JC005248.

    • Search Google Scholar
    • Export Citation
  • Sparrow, M., , and E. Hawker, 2005: RRS James Clark Ross cruise 115, 01 Dec–19 Dec 2004. Drake Passage repeat hydrography: WOCE southern repeat section 1b—Burdwood Bank to Elephant Island. Southampton Oceanography Centre Cruise Rep. 56, 80 pp.

  • Stansfield, K., , and M. Meredith, 2008: RRS James Clark Ross cruise 139, 05 Dec–12 Dec 2005. Drake Passage repeat hydrography: WOCE southern repeat section 1b—Burdwood Bank to Elephant Island. National Oceanography Centre, Southampton Cruise Rep. 24, 72 pp.

  • Sun, C., , and D. R. Watts, 2001: A circumpolar gravest empirical mode for the Southern Ocean hydrography. J. Geophys. Res., 106, 28332855.

    • Search Google Scholar
    • Export Citation
  • Talley, L. D., 1996: Antarctic Intermediate Water in the South Atlantic. The South Atlantic: Present and Past Circulation, G. Wefer et al., Eds., Springer-Verlag, 219–238.

  • Thompson, D. W. J., , and S. Solomon, 2002: Interpretation of recent Southern Hemisphere climate change. Science, 296, 895–899, doi:10.1126/science.1069270.

    • Search Google Scholar
    • Export Citation
  • Thompson, D. W. J., , S. Solomon, , P. J. Kushner, , M. H. England, , K. M. Grise, , and D. J. Karoly, 2011: Signatures of the Antarctic ozone hole in Southern Hemisphere surface climate change. Nat. Geosci., 4, 741749, doi:10.1038/ngeo1296.

    • Search Google Scholar
    • Export Citation
  • Timmermann, R., , A. Worby, , H. Goosse, , and T. Fichefet, 2004: Utilizing the ASPeCt sea ice thickness data set to evaluate a global coupled sea ice–ocean model. J. Geophys. Res., 109, C07017, doi:10.1029/2003JC002242.

    • Search Google Scholar
    • Export Citation
  • Turner, J., and Coauthors, 2009: Non-annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent. Geophys. Res. Lett., 36, L08502, doi:10.1029/2009GL037524.

    • Search Google Scholar
    • Export Citation
  • Verdy, A., , J. Marshall, , and A. Czaja, 2006: Sea Surface temperature variability along the path of the Antarctic Circumpolar Current. J. Phys. Oceanogr., 36, 13171331.

    • Search Google Scholar
    • Export Citation
  • von Schuckmann, K., , F. Gaillard, , and P.-Y. Le Traon, 2009: Global hydrographic variability patterns during 2003–2008. J. Geophys. Res., 114, C09007, doi:10.1029/2008jc005237.

    • Search Google Scholar
    • Export Citation
  • Watanabe, T., , M. Ikeda, , and M. Wakatsuchi, 2004: Thermohaline effects of the seasonal sea ice cover in the Sea of Okhotsk. J. Geophys. Res., 109, C09S02, doi:10.1029/2003JC001905.

    • Search Google Scholar
    • Export Citation
  • Williams, A., , R. Hadfield, , and G. Quartly, 2008: RRS James Clark Ross cruise 163, 07 Dec–15 Dec 2006. Drake Passage repeat hydrography: WOCE southern repeat section 1b—Burdwood Bank to Elephant Island. National Oceanography Centre, Southampton Cruise Rep. 25, 64 pp.

  • Wong, A., , A. Bindoff, , and J. Church, 1999: Large-scale freshening of intermediate waters in the Pacific and Indian Oceans. Nature, 400, 440443, doi:10.1038/22733.

    • Search Google Scholar
    • Export Citation
  • Wong, A., , A. Bindoff, , and J. Church, 2001: Freshwater and heat changes in the North and South Pacific Oceans between the 1960s and 1985–94. J. Climate, 14, 16131633.

    • Search Google Scholar
    • Export Citation
  • Yuan, X., , and C. Li, 2008: Climate modes in southern high latitudes and their impacts on Antarctic sea ice. J. Geophys. Res., 113, C06S91, doi:10.1029/2006JC004067.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 123 123 30
PDF Downloads 45 45 1

Control of Mode and Intermediate Water Mass Properties in Drake Passage by the Amundsen Sea Low

View More View Less
  • 1 University of Southampton, National Oceanography Centre, Southampton, Southampton, United Kingdom
  • | 2 National Oceanography Centre, Southampton, Southampton, United Kingdom
  • | 3 Norwegian Institute for Nature Research, Tromsø, Norway
  • | 4 Scottish Oceans Institute, St. Andrews, United Kingdom
© Get Permissions
Restricted access

Abstract

The evolution of the physical properties of Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) in the Drake Passage region is examined on time scales down to intraseasonal, within the 1969–2009 period. Both SAMW and AAIW experience substantial interannual to interdecadal variability, significantly linked to the action of the Amundsen Sea low (ASL) in their formation areas. Observations suggest that the interdecadal freshening tendency evident in SAMW over the past three decades has recently abated, while AAIW has warmed significantly since the early 2000s. The two water masses have also experienced a substantial lightening since the start of the record. Examination of the mechanisms underpinning water mass property variability shows that SAMW characteristics are controlled predominantly by a combination of air–sea turbulent heat fluxes, cross-frontal Ekman transport of Antarctic surface waters, and the evaporation–precipitation balance in the Subantarctic zone of the southeast Pacific and Drake Passage, while AAIW properties reflect air–sea turbulent heat fluxes and sea ice formation in the Bellingshausen Sea. The recent interdecadal evolution of the ASL is consistent with both the dominance of the processes described here and the response of SAMW and AAIW on that time scale.

Corresponding author address: Sally E. Close, Centre de Recherches sur la Terre et le Climat Georges Lemaître, Earth and Life Institute, Université catholique de Louvain, Place Louis Pasteur 3, 1348 Louvain-la-Neuve, Belgium. E-mail: sally.close@uclouvain.be

Abstract

The evolution of the physical properties of Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) in the Drake Passage region is examined on time scales down to intraseasonal, within the 1969–2009 period. Both SAMW and AAIW experience substantial interannual to interdecadal variability, significantly linked to the action of the Amundsen Sea low (ASL) in their formation areas. Observations suggest that the interdecadal freshening tendency evident in SAMW over the past three decades has recently abated, while AAIW has warmed significantly since the early 2000s. The two water masses have also experienced a substantial lightening since the start of the record. Examination of the mechanisms underpinning water mass property variability shows that SAMW characteristics are controlled predominantly by a combination of air–sea turbulent heat fluxes, cross-frontal Ekman transport of Antarctic surface waters, and the evaporation–precipitation balance in the Subantarctic zone of the southeast Pacific and Drake Passage, while AAIW properties reflect air–sea turbulent heat fluxes and sea ice formation in the Bellingshausen Sea. The recent interdecadal evolution of the ASL is consistent with both the dominance of the processes described here and the response of SAMW and AAIW on that time scale.

Corresponding author address: Sally E. Close, Centre de Recherches sur la Terre et le Climat Georges Lemaître, Earth and Life Institute, Université catholique de Louvain, Place Louis Pasteur 3, 1348 Louvain-la-Neuve, Belgium. E-mail: sally.close@uclouvain.be
Save