[Edge-all] Lecture today (2/4) at 3:30 pm - Lorraine Lisiecki - Pleistocene Glacial Cycles

[Sandra Kirtland Turner]

Hi everyone,

I wanted to share details for the next EPS Hewett Club Speaker, Dr. Lorraine
Lisiecki from the University of California, Santa Barbara.

Dr. Lisiecki is a Professor in the Department of Earth Sciences at UC Santa
Barbara. Her research focuses on computational approaches to interpreting
paleoclimate records, with a particular interest in understanding
Plio-Pleistocene climate evolution, including Milankovitch cycles, 100-kyr
glacial cycles, and deep-ocean circulation. She also develops software for
age model development and stratigraphy, using tools like stratigraphic
correlation, time series analysis, and Bayesian statistics.

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. Lorraine Lisiecki*
Date & Time: *Tuesday, February 4th at 3:30 **PM** - 4:20 PM*
Location:      * Winston Chung Hall 138  *
Grad Lunch:  *Tuesday, **February 4th**, Sub Station in the GEO courtyard
at 12:00 PM*
Dinner:          *“The Getaway” after the talk - 5:00 PM*

*Title: **The Role of Precession in Pleistocene Glacial Cycles *


*Abstract: *Over the past one million years, Earth’s climate variability
has been dominated by large-amplitude glacial cycles, each approximately
100,000 years in duration. The cause of these glacial cycles and their
timing has long been a topic of debate. Leading hypotheses today focus on
climate’s relative sensitivity to two orbital cycles, precession and
obliquity, which each affect the seasonal and latitudinal distribution of
the sun’s energy differently. Identifying the impacts of these two orbital
cycles provides information about the sensitivity of ice sheets and
atmospheric CO2 to changes in radiative forcing and the roles of climate
feedbacks in glacial cycles.


Recent research indicates that the rapid warming following each glacial
maximum is most sensitive to changes in 23,000-year precession cycles,
accompanied by modest sensitivity to 41,000-yr obliquity cycles. These new
results are based on improvements in the accuracy of estimated ages for
benthic δ18O (a proxy for ice volume and ocean temperature) over the past
640,000 years (Hobart et al., 2023). Whereas age estimates of Pleistocene
climate change are most commonly based on assuming certain responses to
obliquity and precession, Hobart et al. (2023) generated ages for benthic δ
18O records by correlating North Atlantic ice rafting events to
radiometrically dated speleothem records of Asian monsoon variability
(Cheng et al., 2016). These new age estimates demonstrate that the timing
of deglaciation (warming and ice melt) has statistically significant
relationships with both obliquity and precession; however, we find a
tighter correlation to precession than obliquity. Furthermore, we find a
particularly strong relationship between the timing of deglacial ice
rafting and precession forcing (Gleason et al., in prep).


Additionally, we find evidence for the precession sensitivity of ice sheets
in the early Pleistocene (prior to 1 Myr ago), a time when most climate
records were dominated by 41,000-yr obliquity cycles. Newly described
differences between benthic δ18O responses in the Atlantic and Pacific
Oceans at ~1.8 Myr ago suggest that Northern and Southern Hemisphere ice
sheets were each responding to local variations in radiative forcing
associated with precession forcing (Zhou et al., 2024). This type of
precession response is difficult to detect in early Pleistocene climate
records because local precession forcing is anti-phased between
hemispheres, causing the northern and southern precession responses to
largely cancel in records of global mean change (Raymo et al., 2006).

-- 
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/20250204/a8badb48/attachment.htm>