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Long-term temperature records in Antarctica: The view from ice cores. David Schneider Department of Earth and Space Sciences University of Washington Seattle, WA 98195 USA. Acknowledgements. Cecelia Bitz – U. Washington Daniel Dixon – U. Maine Joseph Flaherty – U. Washington
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Long-term temperature records in Antarctica: The view from ice cores David Schneider Department of Earth and Space Sciences University of Washington Seattle, WA 98195 USA
Acknowledgements Cecelia Bitz – U. Washington Daniel Dixon – U. Maine Joseph Flaherty – U. Washington Julie Jones – GKSS, Germany Paul Mayewski – U. Maine David Noone – U. Colorado Eric Steig – U. Washington Tas van Ommen – Australian Antarctic Division National Science Foundation Scientific Committee on Antarctic Research
Overview ►Antarctic temperature reconstruction from ice cores ►Climate model applications ►Antarctic connections to global water isotopic records
Temperature variability Correlation r PC1 of T correlation with 2-m T from Polar MM5 “Antarctic hindcast” project (EOF 1)
Temperature variability Correlation r PC1 of T correlation with 2-m T SAM index correlation with 2-m T Surface energy balance implies tight coupling to atmospheric circ.; poleward transport of heat and mass and katabatic winds are modified by SAM
Temperature reconstruction • ►WHY? • We know a fair amount about monthly to interannual variability, nothing about timescales between interannual and glacial • Trend studies, although apparently conflicting, are in agreement when seasonality, period of record, and region are accounted for • SAM signal is robust; SAM explains up to 50% of variance in Antarctic station records & a significant amount of the trends in all seasons • Data only back to 1950s. No clear signal of climate change on the continent outside Peninsula
Temperature reconstruction ►APPROACH • ►δ18O and δD records gathered from multiple locations (ITASE traverses, Law Dome, Dronning Maud Land) • ►Dating: • Annual layers reasonably obvious • Volcanic signatures • Radar traces of isochrons between some sites 200-year cores used in this study
Temperature reconstruction ►APPROACH • Prediction: • Multiple records will share SAM-related signal • In addition, Rayleigh models give δ-T relationship • Isotopic spatial signal analogous to T signal Model prediction of SAM signal in isotopes (Noone and Simmonds, 2002)
Temperature reconstruction ►APPROACH Correlation r Ice core stack shows significant correlation with temperatures, also with SAM directly but less significant
Temperature reconstruction ►RESULTS ► Direct calibration from instrumental records ► Remarkable variability in long record ► Late 20th century temperatures (1961-1999) were ~0.20°C higher than late 19th century temperatures (1861-1899)
Temperature reconstruction ►RESULTS ► SAM explains anti-correlation of Orcadas T record and reconstructed continental T record ►Independent SAM reconstructions (e.g. Jones and Widmann, 2003) are consistent with this reconstruction
Temperature reconstruction ►RESULTS ► Orcadas (and perhaps the rest of the AP region) has experienced much 20th-century warming; the continent has not. ► Notably, however, the reconstructed continental record is largely in-phase with the global mean; the Orcadas record is not.
Climate model applications ►Uses of models: 1) Data – model comparison; e.g. Antarctic T reconstruction vs. model temperature Late 20th century minus late 19th century Surface warming under SRES A1B in CCM3 ► Polar amplification? ► Just a continental effect? ► What are the model deficiencies? ► Has the reconstruction missed something?
Climate model applications ►Uses of models: 2) Model prediction of proxy quantity, compare to reality DJF δ180 in NCAR atmosphere model (Noone, unpublished) Isotopic signature of SAM in MUGCM (Noone and Simmonds, 2002) ► Water isotopic schemes are much improved in recent years. Isotopic tracers are now in the atmospheric version of the NCAR CCSM3, in addition to older schemes in the GISS models.
Antarctic connections to globe ►Uses of models: 3) Model – data integration Water isotope “prediction” for a particular day constrained by reanalysis ►Proposed global-scale synthesis ► Opportunities for collaborations. ► Model output useful for identifying future sites, examining teleconnections. ► Reconstructions constrained by model physics and a wealth of proxy data.
