Proxy Development

3-OH-FAs (3-Hydroxy Fatty Acids)

My group is working across disciplines with microbiologists and ecologists on the first systematic global surveys of 3-OH-FA biomarkers (3-OH-FAs – originating from bacteria), in soils, lakes and marine sediments. We were the first to calibrate 3-OH-FAs for reconstructing terrestrial temperature and pH in soils (2016, 2021) lakes (2021) and to apply 3-OH-FAs to a paleoclimate archive, using samples from a stalagmite to reconstruct temperature and hydrological changes over the last 9000 years (Wang, Bendle et al., 2018, 2019). These, hitherto overlooked, bacterial membrane lipids have wide-spread applicability and open up new avenues of molecular and isotopic research in paleoclimatology for both terrestrial and marine settings (see Header Image above). We are now working towards parallel studies of biomarkers paired with aDNA analyses.

Machine Learning

I am working closely with Prof. Ilya Mandel, and colleagues at Birmingham to pioneer the first machine learning based calibrations for GDGT biomarkers. We are now exploring these techniques for the development of 3-OH-FA biomarker based paleoclimate proxies (see OPTiMAL). These Gaussian Process (GP) based calibrations reduce the root mean square uncertainty on predictions, compared to two dimensional linear regressions. GP calibrations search among a large space of smoothly varying functions of biomarker compositions for those functions which adequately describe environmental parameter variability, e.g.: temperature, pH, bacterial ecology. We recently published the first application using OPTiMAL to reconstruct climatic change from the margins of the Antarctic over the last 45 myr.

Algal Biomarker Isotopic Proxies for Antarctic Climate Change

We recently published the first paleoclimate reconstruction to use algal biomarker hydrogen isotopes, as a proxy for Antarctic glacial meltwater inputs during the Holocene, which follows the pioneering use of this proxy by Pagani et al. (2006) for polar freshwater inputs in the Arctic in the Eocene. We are doing this to tackle the mismatch between both modern and paleoclimate observations and model predictions and address two key outstanding and interlinked questions  “What drove the rapid Neoglacial sea-ice expansion in the mid Holocene” and “What is driving the recent rise and fall of Antarctic sea ice?”. We are also exploring algal biomarker carbon isotopes as indicators of marine Antarctic paleo-productivity.

Previous Work

Biomarkers in ice archives

I was part of a team that was the first to successfully measure organic biomarkers originating from terrestrial plants and soils (and transported by wind) extracted from an ice-core, finding evidence of greater transport of fine, carbonaceous dust to the Arctic during positive phases of the Arctic Oscillation (AO). This study has implications for future climate scenarios. An increasingly positive phase AO is a predicted response to anthropogenic greenhouse gas forcing. In such a scenario, our work predicts that supplies of Asian dust to the Arctic would increase further amplifying future warming (acting as a positive feedback).

Biomarkers in atmospheric dust

During my JSPS Post-Doctoral Fellowship at Hokkaido University (Japan) I studied the carbon cycle in the western Pacific to the Southern Ocean by using the molecular and isotopic distributions of lipid compounds present in aerosols as tracers.

Alkenones and GDGTs

My early career interests included the development and refinement of alkenone proxies for SST (U^K₃₇), water-mass (%C_37:4) and past sea-level change. I also developed calibrations and explored caveats for applying GDGT based proxies in tropical to high-latitude continental shelf settings.