#  ClimaTea Journal Club 

 



####  calendar\_today Date and Time 

 **October 15, 2019** 

 03:00PM - 03:00PM EDT 

####  pin\_drop Location 

 **HUCE Seminar Room MCZ 429**  



 

 



 

 **Speaker:** Katherine Keller

 Katherine facilitate a discussion on the Thomas Chalk et al. (2017) [paper](/file_url/602) **"****Causes of ice age intensification across the Mid-Pleistocene Transition"**

 Here's the abstract:

 During the Mid-Pleistocene Transition (MPT; 1,200–800 kya), Earth’s orbitally paced ice age cycles intensified, lengthened from ∼40,000 (∼40 ky) to ∼100 ky, and became distinctly asymmetrical. Testing hypotheses that implicate changing atmospheric CO2 levels as a driver of the MPT has proven difficult with available observations. Here, we use orbitally resolved, boron isotope CO2 data to show that the glacial to interglacial CO2 difference increased from ∼43 to ∼75 μatm across the MPT, mainly because of lower glacial CO2 levels. Through carbon cycle modeling, we attribute this decline primarily to the initiation of substantive dust-borne iron fertilization of the Southern Ocean during peak glacial stages. We also observe a twofold steepening of the relationship 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 expected from the removal of subglacial regolith or interhemispheric ice sheet phase-locking. We argue that neither ice sheet dynamics nor CO2 change in isolation can explain the MPT. Instead, we infer that the MPT was initiated by a change in ice sheet dynamics and that longer and deeper post-MPT ice ages were sustained by carbon cycle feedbacks related to dust fertilization of the Southern Ocean as a consequence of larger ice sheets.



 

 



 

 See also:- [ ClimaTea ](/type-event/climatea-lecturejournal-club)
 
 

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