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NACLIM annual meeting 2013, Trieste

Predictability of North Atlantic subpolar gyre strength with focus on the mid-1990s weakening. Katja Lohmann , Daniela Matei , Johann Jungclaus. NACLIM annual meeting 2013, Trieste. Motivation. Blue Whiting catches. Mid-1990s weakening of subpolar gyre

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NACLIM annual meeting 2013, Trieste

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  1. Predictability of North Atlantic subpolar gyre strength with focus on the mid-1990s weakening KatjaLohmann, Daniela Matei, Johann Jungclaus NACLIM annualmeeting2013, Trieste

  2. Motivation Blue Whitingcatches • Mid-1990s weakeningof subpolar gyre • followedby large biogeographicalshift in • northeastern North Atlantic • was caused not onlybyatmosphericforcing, but also oceaninitialstate Hatun et al., 2009

  3. Predictionsystem • PreCMIP5 predictionexperiments (Matei et al., 2012a, b) 19482007 Assimilation run: coupled model simulation with data assimilation (T and S anomalies from ocean model simulation forced with atmospheric reanalysis fields) 10 years • Initialized hindcasts: • coupled model simulations with inititial conditions from assimilation run • 1 hindcast every year • every 5th year plus in 1990s: 3 hindcasts Mateiet al. (2012b): Two tales of initializing decadal climate predictions experiments with the ECHAM5/MPI-OM model. Journalof Climate, 25, 8502-8523 Mateiet al. (2012a): Multiyear prediction of monthly mean Atlantic Meridional Overturning Circulation at 26.5oN. Science, 335 (6064), 76-79 Construct time seriesaccordingtolead time

  4. Predictionsystem Subpolar gyreindex: Minimum of subpolar barotropicstreamfunction (maximumgyrestrength)

  5. Predictabilityof subpolar gyrestrength

  6. Predictabilityof subpolar gyrestrength

  7. Predictabilityof subpolar gyrestrength Subpolar gyreindex: assimilationrun, individual hindcasts, meanofhindcasts

  8. Predictabilityof subpolar gyrestrength Subpolar gyreindex: assimilationrun, individual hindcasts, meanofhindcasts

  9. Predictabilityof subpolar gyrestrength Why mid-1990s weakeningwithrespectto area-averagedgyrestrengthlesspredictable?

  10. Conclusions • Apart frompredictiveskillbased on relativelylong time series, predictabilityofcertainevents (casestudies) isofinterest • Mid-1990s weakeningof subpolar gyre, withrespecttomaximumgyrestrength, mainlycausedbyoceaninitialstateandthereforemorepredictablethansubpolar gyrestrength in general • Weakeningof subpolar gyreisfound in hindcastsfromabout 1991 on; oceaninitialstatein 1994 and 1995 sufficienttopredict a realisticamplitudeofweakening in all hindcasts

  11. Predictability of sea surface temperature and sea ice in the Nordic Seas (Helene Langehaug et al.) 19602010 10 years Initialized hindcastsfrom CMIP5: Several hindcastsevery 5th year Construct time seriesaccordingtolead time, whicharecomparedtoHadISST

  12. Predictability of sea surface temperature and sea ice in the Nordic Seas (Helene Langehaug et al.) COR skillseasurfacetemperature Inflowof warm Atlanticwaterleadstopredictiveskillofeastern Nordic Seas / Barents SeaseasurfacetemperatureaswellasBarents Seaseaice?

  13. Thank you! The research leading to these results has received funding from the European Union 7th Framework Programme (FP7 2007-2013) under grant agreement n.308299 (NACLIM).

  14. Predictionsystem

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