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SUMMARY:Seawater calcium concentration may be a key driver of long-term pC
 O2 - David Evans\, University of Southampton
DTSTART:20230606T110000Z
DTEND:20230606T120000Z
UID:TALK177035@talks.cam.ac.uk
CONTACT:Oscar Branson
DESCRIPTION:The drawdown of CO2 via the temperature-dependent weathering o
 f silicate minerals is canonically thought to be one of the key processes 
 acting to maintain Earth’s climate within narrow bounds. However\, the c
 limatic responsiveness of weathering on multi-million-year timescales\, to
  my knowledge\, remains to be demonstrated. If no such relationship exists
 \, or is weaker than typically presumed\, previously unexplored factors ma
 y be important in driving long-term carbon cycle changes. One such paramet
 er may be the calcium concentration of seawater\, via the effect that it h
 as on CaCO3 preservation in the ocean\, explored here using a new\, near-c
 ontinuous Cenozoic record of seawater major ion chemistry. The Cenozoic [C
 a2+sw] record closely corresponds to the timing of atmospheric CO2 changes
 \, potentially implying a common driver. Testing the causality of this rel
 ationship using a carbon cycle box model demonstrates that whether or not 
 this is the case depends to a large degree on the slope of the relationshi
 p between climate and silicate weathering\, with a shallow slope implying 
 that [Ca2+sw] is likely to drive the system. Given the recently identified
  major change in the Neogene global sea floor spreading rate\, this findin
 g potentially shifts the key driver of long-term climate from the terrestr
 ial to marine realm\, and at the very least\, highlights the need to deter
 mine whether silicate weathering is responsive to climate change on geolog
 ic timescales before the long-term drivers of CO2 can be determined.\n\n
LOCATION:Department of Earth Sciences\, Tilley Lecture Theatre
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