"Assessing the strength of climate feedbacks, and their dependence on climate mean state, from paleoclimate records"

Bradley Markle

Assistant Professor, CU Boulder, INSTAAR and Earth Science

Summary - Geochemical records from ice cores and other archives can provide proxies of environmental conditions over a vast range of timescales from sub-annual to multi-millennial. The relationship between variability at different timescales can inform us about the dominant forcing on the Earth’s climate system, such as changes in insolation owing to the Earth’s orbit and variations in it. The relationships between variability across these timescales can also inform us about features internal to the Earth system such as thermal inertia and feedback processes, which each have distinct influence on the spectra of climate variations (that is how the amplitude of variations depend on the timescale we examine). Investigation of the spectra of ice-core geochemical records can thus inform us about these internal climate process, like feedbacks, and how they vary with mean climate. These influences on proxy spectra must contend with nuances of the proxies themselves. This includes depositional noise which could overwhelm information about the climate. Post-depositional process can also dramatically influence the spectra recorded in ice-core geochemistry, such as the well-known influence of vapor diffusion in the firn on water isotope ratios.  By analyzing spectra of multiple distinct proxies, we can investigate the relative influence of large-scale climate and local proxy-specific processes on these spectra. Here we combine data, modeling, and theory to disentangle these influences.

Bio 

• In general my research is in the climate system and how it varies across timescales. Especially icy places and the polar regions.

• I did my PhD at the University of Washington (2017), and did some postdocs after -a short one at UW, a slightly longer one at UC Santa Barbara, and a longer one at Caltech.

• I started here at CU in the fall of 2020 - a pleasant and calm time to start a new faculty job (this is a joke).

• I get to work with a lot of great people here at INSTAAR. I'm co-advising students with Tom Marchitto, Bob Anderson, and Tyler Jones. I get to work with all the wonderful people in the Stable Isotope Lab

• I'm also the Director of Academic of the Juneau Icefield Research Program (a CU sponsored summer school in Alaska https://www.juneauicefield.org/). Many of our CU undergrads attend, many of our INSTAAR grad students have attended as researchers, teaching instructors, and (as of this year) as student on our new graduate course. INSTAAR faculty can join as researchers and/or teaching faculty. Everyone should apply!

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INSTAAR Seminar Series

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Audience: All are welcome

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