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SUMMARY:How are water isotopes influencing our understanding of Antarctic 
 climate variability over the past 2000 years? - Anaïs Orsi
DTSTART:20210318T150000Z
DTEND:20210318T160000Z
UID:TALK156100@talks.cam.ac.uk
CONTACT:Daniel Field
DESCRIPTION:Under the current global warming trend\, the Arctic is warming
  the\nfastest\, and strangely\, many parts of Antarctica are not warming a
 t all.\nThe delayed response of the high latitudes of Southern Hemisphere 
 to the\nGreenhouse warming is an important observation that is not reprodu
 ced by\nthe current generation of global climate models. One of the leadin
 g\nhypotheses to explain this discrepancy is that natural variability is\n
 particularly large in the southern high latitudes\, masking the\nanthropog
 enic forcing\, and that this large variability is not well\nreproduced by 
 models. Quantifying internal variability and understanding\nits cause is i
 mportant for our understanding of the potential response\nof Antarctica to
  climate change\, and to improve projections.\nHere\, we will review our k
 nowledge of Antarctic climate variability from\nice cores covering the pas
 t 2000 years. This is an interval sufficiently\nshort to have observations
  from many places in Antarctica\, and\nsufficiently long to investigate va
 riability at decadal and longer\ntimescales. Temperature reconstructions c
 ome mainly from water isotopes\,\nbut they are not a perfect temperature r
 ecorder. The central thread of\nthis talk will be to discuss how our visio
 n of climate variability is\ndistorted by the water-isotopes lens. We will
  discuss the importance of\nprecipitation bias on the deposited ice water 
 isotope signal\, using\nisotope enabled climate models over the reanalysis
  period\n(1979-present)\, and illustrate the impact of this sampling bias 
 by\ncontrasting the expression of circulation modes (such as the SAM) on\n
 temperature and d18O. In the second part of the talk\, we will review\nevi
 dence from other temperature proxies\, especially borehole temperature\nre
 cords and temperature reconstructions from inert gas isotopes\n(d15N-exces
 s)\, and discuss how the different records can be reconciled\ninto a coher
 ent view of Antarctic climate evolution over the past 2ka.\nIf time allows
 \, we will briefly discuss model-data comparisons over the\nlast millenniu
 m\, and review hypothesis about why models (OA-GCM)\nunder-estimate intern
 al variability in the high latitude Southern\nHemisphere.
LOCATION:Zoom Seminar
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