BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Causes of ice-age intensification across the Mid-Pleistocene Trans
 ition\, insights from a new boron isotope CO2 record - Thomas Chalk\, Nati
 onal Oceanography Centre\, Southampton
DTSTART:20170309T173000Z
DTEND:20170309T183000Z
UID:TALK69460@talks.cam.ac.uk
CONTACT:Dr Rachael Rhodes
DESCRIPTION:During the Mid-Pleistocene Transition (MPT\; 1200–800 thousa
 nd years ago\, kyrs) Earth’s orbitally paced ice-age cycles intensified\
 , lengthened from ~40 to ~100 kyrs\, and became distinctly asymmetrical. T
 esting hypotheses that implicate changing atmospheric CO2 levels as a driv
 er of the MPT has proven difficult with available observations. Here we us
 e orbitally resolved\, boron-isotope CO2 data to  demonstrate that the gla
 cial-to-interglacial CO2 difference increased from ~43 to ~75 µatm across
  the MPT\, mainly due to lower CO2 levels during glacials. Through carbon-
 cycle modelling\, we attribute this decline primarily to the initiation of
  substantive dust-borne iron fertilization of the Southern Ocean during pe
 ak glacial stages. We also observe a two-fold steepening of the relationsh
 ip between sea level and CO2-related climate forcing that is suggestive of
  a change in the dynamics that govern ice-sheet stability\, such as that e
 xpected from the removal of subglacial regolith. We argue that neither ice
 -sheet dynamics nor CO2 change in isolation can explain the MPT. Instead\,
  we infer that the MPT initiated by a change in ice-sheet dynamics\, and t
 hat longer and deeper post-MPT ice ages were sustained by carbon-cycle fee
 dbacks related to dust fertilization of the Southern Ocean as a consequenc
 e of larger ice sheets.\n\n\nThis talk is part of the Quaternary Discussio
 n Group (QDG).
LOCATION:Latimer Room (Old Court)\, Clare College\, Trinity Lane
END:VEVENT
END:VCALENDAR