[Edge-all] Hewett Club Lecture Tuesday January 14: Dr. Mathis Hain

[Sandra Kirtland Turner]

Hi everyone,

We are pleased to announce the first Hewett Club Speaker of 2025, Dr.
Mathis P. Hain from the University of California, Santa Cruz.
Dr. Hain is an Associate Professor in the Departments of Earth and
Planetary Sciences and Ocean Sciences at UC Santa Cruz. His research
focuses on advancing our understanding of natural geochemical, biological,
and physical Earth system processes, with particular attention to their
interactions over time. He also uses computational methods to reconstruct
the biogeochemical evolution of the ocean and atmosphere, with a special
emphasis on the global carbon cycle and the biological utilization of
nutrients in the ocean.

Please note that the seminar will be held in *Winston Chung Hall 138*.

There will be *Tuesday Tea Time at 3:00 pm* before the talk in the GEO
hallway. Come grab snacks and coffee or tea and socialize before the talk!

Speaker:        *Dr. Mathis P Hain*
Date & Time: *Tuesday, January 14th at 3:30 **PM** - 4:20 PM*
Location:      * Winston Chung Hall 138  *
Dinner:          *“The Getaway” after the talk - 5:00 PM*

*Abstract: CO2 in Earth’s Ice Age Cycles *
This talk is about the observed but not fully explained reduction of
atmospheric carbon dioxide (CO2) at the peaks of recurring ice ages of the
last million or more years. The “ice age CO2 problem” is that we need to
understand the climatic influences that regulate CO2 change before we can
learn what role CO2 played in shaping ice age climate cycles.

Here we describe an analytical framework that accurately predicts
preindustrial atmospheric CO2 from mean ocean data (black marker), and we
use it to project CO2 changes for key ice age changes and CaCO3compensation
(solid/dashed arrows). We find that direct “Climate Change”
effects—reconstructed ice sheet growth, cooling and the contraction of
terrestrial carbon stocks—reduce CO2 by only 4%, from 280 to 267 ppm. Early
hypotheses trying to link ice sheet-driven sea level lowering to increases
in the weathering supply of alkalinity and phosphate nutrient to the ocean
have largely been contradicted by reconstructions of deep ocean calcite
saturation horizon (CSH), global ocean productivity, and the sequencing of
deglacial events. Plausible changes in the efficiency of the ocean’s
biological pump, most easily driven by changes in the Southern Ocean, would
lower atmospheric CO2 by 25% in large part by raising ocean alkalinity by
59µmol/kg, with a 136µmol/kg decline in average deep ocean O2. If we allow
for no more than 200m of steady state CSH deepening, then the direct
“Climate Change” effects and “Ocean Biological Pump” effects, taken
together, account for 29% CO2 reduction (280 to 199ppm), with mean
alkalinity rising from 2364 to 2551µmol/kg, and deep ocean O2 declining
from 165 to 49µmol/kg.

We find that nine environmental factors effectively determine steady state
CO2 in the atmosphere, but their individual effects are not additive but
rather must be multiplied. Consequently, the radiative climate forcing
attributed to each environmental factor simply adds up. Our analytical
framework can be used both to assimilate diverse paleo reconstructions and
to quantitatively diagnose numerical carbon cycle models, opening new ways
of data-driven modeling of the Earth system.

Thank you,
Gayatri, Anthony, Xianglin, Ginny, and Karlee

-- 
Sandra Kirtland Turner, Ph.D.
Associate Professor of Paleoclimate/Paleoceanography
Vice-chair, Department of Earth and Planetary Sciences
Director, Environmental Dynamics and GeoEcology (EDGE) Institute
University of California, Riverside
Riverside, CA  92521
(951) 827-3191 (office)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.ucr.edu/pipermail/edge-all/attachments/20250113/fbd58c70/attachment.htm>