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SUMMARY:Overturning ideas: Using the mean state of the ocean to understand
  its role in transient climate change - Jan Zika\, National Oceanography C
 entre\, Southampton
DTSTART:20141029T110000Z
DTEND:20141029T120000Z
UID:TALK53736@talks.cam.ac.uk
CONTACT:Dr. Joakim Kjellsson
DESCRIPTION:I will start by asking how we can detect changes in the global
  water cycle from changes in ocean salinity. The water cycle transports ov
 er 2.5 x 10^9 litres of fresh water from high salinity regions to low sali
 nity regions of the surface ocean every second. This fresh water is return
 ed within the ocean by mixing. I frame this balance in terms of a distribu
 tion function of water mass in salinity coordinates. The distribution is m
 ade wider by the water cycle – creating greater contrast between high an
 d low salinity – and collapsed by mixing – bringing these waters back 
 towards a single salinity. The latter is characterised by an e-folding tim
 escale of approximately 50 years. The salinity distribution has been found
  to widen over the observational period suggesting an amplification of the
  water cycle of approximately 3%.\n\nI will then investigate the mechanism
 s by which heat is transported from the earth’s surface to the ocean int
 erior offsetting global warming. To this end I will project ocean circulat
 ion into pressure-temperature coordinates - analogous to the Carnot Diagra
 m of classical thermodynamics. Traditional models describe the deep circul
 ation as a thermally direct ‘heat engine’ balanced by vertical mixing.
  It is suggested here that the deep ocean may have both a thermally direct
  and a thermally indirect ‘heat pump’ component – the latter driven 
 by either wind and/or salinity effects. The two components of the circulat
 ion\, the pump and the engine\, can balance one and other in steady state.
  As the surface of the ocean warms under transient climate change\, the pu
 mp continues to warm the deep ocean while the engine can be temporarily ex
 tinguished. Whether the ocean is purely a weak heat engine or has both a v
 igorous engine and pump is a strong predictor of how fast the ocean will a
 bsorb heat with global warming.\n\nFinally\, I will review some recent wor
 k on distilling the ‘thermohaline circulation’ of the ocean and the an
 alogous ‘hydrothermal circulation’ of the atmosphere using thermodynam
 ic coordinates and discuss opportunities for future work.\n\n
LOCATION:British Antarctic Survey\, Room 307
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