"What chemical signatures can we use to trace ancient climate change?"

My role on the cruise

As a palaeoclimatologist, trained in molecular biogeochemistry, I am interested in the source, structure, and distribution of naturally occurring compounds or biomarkers. Biomarkers can tell us a great deal about modern and ancient environments. Certain compounds (especially lipids) are quite resistant to decay, so after the producer organisms expire they are preserved in sediments as sort of molecular fossils. On the cruise I will be collecting water, sea-ice and sediment samples for biomarker analysis. If we understand what environmental factors control the distribution of such compounds in the modern environment and we can find them in ancient sediments, they can be used to reconstruct changes in parameters such temperature over thousands to millions of years; allowing us to reconstruct past changes in climate.
  

My institution

I am a Lecturer and group leader of the  new Glasgow Molecular Organic Geochemistry Laboratory (D-MOL) at the University of Glasgow.

Personal thoughts on the cruise

What are you most looking forward to about the cruise?
"The Aurora Borealis and a few “naval strength” sundowners made with sea-ice!"

What will you miss most when you are away?

"My little boy George, I’ll get back just in time for his 2nd birthday."

What are you dreading most about this cruise?

"Nothing, just the pile of work will build up while I’m away."

What was your most exciting experience on a cruise?

"Getting into a force 11 storm in the North Atlantic on the RRS James Cook."

What was your worst experience on a cruise?

"Getting into a force 11 storm in the North Atlantic on the RRS James Cook."

More detail about my science

Most palaeoclimate proxy records are concentrated in the mid- to low-latitudes, far fewer records are available from the sub-polar and polar environments. However, recent advances in biomarker¹ techniques mean that there are now available a number of proxies which can be applied to reconstruct climate variables from Arctic shelf sediment cores. We wish to examine the link between distribution of these proxies to their precursor organisms and modern environmental parameters in the Arctic. This will give insights into modern biogeochemical processes and will help to refine their palaeoceanographic application.

We wish to collect samples to conduct a full organic geochemical investigation of the biomarker distributions in the recent sediment, sea-water and sea-ice samples. We require 5-20g sediment per sample for sediments. For sea-water samples >10 litres of water filtered for particulate organic matter would be the ideal. We hope to explore this unique opportunity to collaborate with marine microbiologists to conduct in-situ measurements and experiments to identify precursor organisms and to calibrate/tune the biomarker proxies to measured  environmental, climate and hydrological data.

We are also keen to explore opportunities to conduct batch culture experiments using known or suspected precursor organisms; to evaluate the influence of  changes in sea water temperature, salinity, light and nutrients on various biomarker proxies.

The aim is to measure the distributions/variations of multiple biomarkers in sediments, water and ice. Specific biomarkers of interest include:

1. IP25, a novel biomarker produced by sea-ice algae, may be used to reconstruct palaeo sea ice cover. Further work is needed to confirm which sea-ice algae produce this compound and how closely the its occurrence can be calibrated to sea ice-cover.
2. Alkenones (produced by hapotphyte algae). Alkenones are mostly produced by the coccolithophore Emiliania Huxleyi in the mid to low latitudes. It is not clear if E.Huxleyi is responsible for polar water production of alkenones. E.huxleyi is rare in polar waters and may be difficult to identify (especially as fossils in sediments) as it may occur as a naked (coccolith free) variety. Alkenones in polar and sub-polar waters are characterised by an unusual “fingerprint” with high relative abundances of the tetra-unsaturated alkenone (%C37:4). It has been proposed that this tetra-unsaturated alkenone could be a novel biomarker for sea-surface salinity and water mass. Further work needs to be done to indentify the source organism of polar/sub-polar alkenones and to clarify the relationship of such alkenones to environmental parameters.
3. Glycerol Diether Glycerol Tetraethers, produced by both marine crenarchaea and terrestrial bacteria (in the latter case these may have been eroded and transported to fjordic/coastal sites). GDGTs may be used to reconstruct changes in relative inputs of marine versus terrestrial organic matter (the BIT index) and temperatures (both marine SST from the TEX86 index and terrestrial soil temp from the MBT index).
4. Higher plant wax n-alkanes, n-alkanoic acids and n-alkanols. Higher plant waxes can record the transport of terrestrial organic material (fluvially or by atmospheric transport) to the remote Arctic ocean.
5. Additionally we wish to link the relative abundances of different biomarker classes to changes in the productivity of different algal groups (e.g. dinosterol for dinoflagellates, alkenones for haptophytes, highly branched isoprenoids and brassicasterol for diatoms).

We will also conduct compound specific isotopic analysis on the samples collected from the cruise. Examples of how compound specific isotopic analysis could be applied include:

• Investigations of how compound specific delta-D measurements of algal biomarkers relate to changes in the ocean water delta-D, which itself is a function of changes in temperature, upwelling, evaporation/precipitation and sea-ice controlled air-sea exchange.
• To obtain compound specific AMS 14C dates to elucidate differences in the marine carbon reservoir ages for different algal and bacterial classes (both variations between the different sedimentary biomarker classes and variations over time).

¹ The term “biomarker” refers to an organic compound found in the modern environment or geosphere and which can be linked to a precursor organism

James'
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